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AimsQuantile regression is an alternate type of regression analysis that has been shown to have numerous advantages over standard linear regression. Unlike linear regression, which uses the mean to fit a linear model, quantile regression uses a data set's quantiles (or percentiles), which leads to a more comprehensive analysis of the data. However, while relatively common in other scientific fields such as economic and environmental modeling, it is infrequently used to understand biological and microbiological systems.Methods and resultsWe analyzed a set of bacterial growth rates using quantile regression analysis to better understand the effects of antibiotics on bacterial fitness. Using a bacterial model system containing 16 variant genotypes of the TEM β-lactamase enzyme, we compared our quantile regression analysis to a previously published study that uses the Tukey's range test, or Tukey honestly significantly difference (HSD) test. We find that trends in the distribution of bacterial growth rate data, as viewed through the lens of quantile regression, can distinguish between novel genotypes and ones that have been clinically isolated from patients. Quantile regression also identified certain combinations of genotypes and antibiotics that resulted in bacterial populations growing faster as the antibiotic concentration increased-the opposite of what was expected. These analyses can provide new insights into the relationships between enzymatic efficacy and antibiotic concentration.ConclusionsQuantile regression analysis enhances our understanding of the impacts of sublethal antibiotic concentrations on enzymatic (TEM β-lactamase) efficacy and bacterial fitness. We illustrate that quantile regression analysis can link patterns in growth rates with clinically relevant mutations and provides an understanding of how increasing sub-lethal antibiotic concentrations, like those found in our modern environment, can affect bacterial growth rates, and provide insight into the genetic basis for varied resistance.

BackgroundAquatic opportunistic pathogen Aeromonas hydrophila, known to persist in low-nutrient chlorinated waters, can cause life-threatening infections. Two intensive care units experienced a cluster of Aeromonas infections following outdoor temperature spikes coinciding with recurrent plumbing issues, with fatalities due to severe underlying comorbidities co-occurring with extensively-drug resistant (XDR) Aeromonas.MethodsWe investigated this cluster using whole genome sequencing to assess genetic relatedness of isolates and identify antimicrobial resistance determinants. Three A. hydrophila were isolated from patients staying in or adjacent to rooms with plumbing issues during or immediately after periods of elevated outdoor temperatures. Sinks and faucets were swabbed for culture.ResultsAll A. hydrophila clinical isolates exhibited carbapenem resistance but were not genetically related. Diverse resistance determinants corresponding to extensively-drug resistant were found, including co-occurring KPC-3 and VIM-2, OXA-232, and chromosomal CphA-like carbapenemase genes, contributing to major treatment challenges. All 3 patients were treated with multiple antibiotic regimens to overcome various carbapenemase classes and expired due to underlying comorbidities. Environmental culture yielded no Aeromonas.ConclusionsWhile the investigation revealed no singular source of contamination, it supports a possible link between plumbing issues, elevated outdoor temperatures and incidence of nosocomial Aeromonas infections. The diversity of carbapenemase genes detected in these wastewater-derived Aeromonas warrants heightened infection prevention precautions during periods of plumbing problems especially with heat waves.

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii (CRAb) is 1 of the most problematic antimicrobial-resistant bacteria. We sought to elucidate the international epidemiology and clinical impact of CRAb. METHODS: In a prospective observational cohort study, 842 hospitalized patients with a clinical CRAb culture were enrolled at 46 hospitals in five global regions between 2017 and 2019. The primary outcome was all-cause mortality at 30 days from the index culture. The strains underwent whole-genome analysis. RESULTS: Of 842 cases, 536 (64%) represented infection. By 30 days, 128 (24%) of the infected patients died, ranging from 1 (6%) of 18 in Australia-Singapore to 54 (25%) of 216 in the United States and 24 (49%) of 49 in South-Central America, whereas 42 (14%) of non-infected patients died. Bacteremia was associated with a higher risk of death compared with other types of infection (40 [42%] of 96 vs 88 [20%] of 440). In a multivariable logistic regression analysis, bloodstream infection and higher age-adjusted Charlson comorbidity index were independently associated with 30-day mortality. Clonal group 2 (CG2) strains predominated except in South-Central America, ranging from 216 (59%) of 369 in the United States to 282 (97%) of 291 in China. Acquired carbapenemase genes were carried by 769 (91%) of the 842 isolates. CG2 strains were significantly associated with higher levels of meropenem resistance, yet non-CG2 cases were over-represented among the deaths compared with CG2 cases. CONCLUSIONS: CRAb infection types and clinical outcomes differed significantly across regions. Although CG2 strains remained predominant, non-CG2 strains were associated with higher mortality. Clinical Trials Registration. NCT03646227.

The dissemination of antibiotic resistance in Escherichia coli poses a significant threat to public health worldwide. This review provides a comprehensive update on the diverse mechanisms employed by E. coli in developing resistance to antibiotics. We primarily focus on pathotypes of E. coli (e.g., uropathogenic E. coli) and investigate the genetic determinants and molecular pathways that confer resistance, shedding light on both well-characterized and recently discovered mechanisms. The most prevalent mechanism continues to be the acquisition of resistance genes through horizontal gene transfer, facilitated by mobile genetic elements such as plasmids and transposons. We discuss the role of extended-spectrum β-lactamases (ESBLs) and carbapenemases in conferring resistance to β-lactam antibiotics, which remain vital in clinical practice. The review covers the key resistant mechanisms, including: 1) Efflux pumps and porin mutations that mediate resistance to a broad spectrum of antibiotics, including fluoroquinolones and aminoglycosides; 2) adaptive strategies employed by E. coli, including biofilm formation, persister cell formation, and the activation of stress response systems, to withstand antibiotic pressure; and 3) the role of regulatory systems in coordinating resistance mechanisms, providing insights into potential targets for therapeutic interventions. Understanding the intricate network of antibiotic resistance mechanisms in E. coli is crucial for the development of effective strategies to combat this growing public health crisis. By clarifying these mechanisms, we aim to pave the way for the design of innovative therapeutic approaches and the implementation of prudent antibiotic stewardship practices to preserve the efficacy of current antibiotics and ensure a sustainable future for healthcare.

This study investigated the prevalence and antimicrobial resistance (AMR) of Escherichia coli (E. coli) in Nile tilapia from fresh markets and supermarkets. A total of samples (n = 828) were collected from Nile tilapia including fish flesh (n = 276), liver and kidney (n = 276), and intestine (n = 276). Overall prevalence of fecal coliforms (61.6%) and E. coli (53.0%) were observed. High prevalence of E. coli was found in the intestine (71.4%), followed by the liver and kidney (45.7%). The highest prevalence of resistance was commonly found against tetracycline (78.5%), ampicillin (72.8%), and sulfamethoxazole (45.6%) with resistance to only tetracycline (15.2%) as the most common antibiogram. The prevalence of multidrug resistance (MDR) (54.4%) and Extended-spectrum beta-lactamases (ESBLs) (5.7%) were examined. The predominant virulence genes (n = 158) were st (14.6%), followed by eaeA (0.6%). The blaTEM (73.4%), tetA (65.2%), and qnrS (57.6%). There is statistical significance between Nile tilapia from fresh markets and supermarkets. Based on logistic regression analysis, ampicillin-resistant E. coli was statistically associated with the phenotypic resistance to tetracycline and trimethoprim, and the presence of blaTEM and tetA (p < 0.05). Further investigation of AMR transference and their mechanisms is needed for AMR control.

AmpC enzymes are a class of beta-lactamases produced by Gram-negative bacteria, including several Enterobacterales. When produced in sufficient amounts, AmpCs can hydrolyze third-generation cephalosporins (3GCs) and piperacillin/tazobactam, causing resistance. In Enterobacterales, the AmpC gene can be chromosomal- or plasmid-encoded. Some species, particularly Enterobacter cloacae complex, Klebsiella aerogenes, and Citrobacter freundii, harbor an inducible chromosomal AmpC gene. The expression of this gene can be derepressed during treatment with a beta-lactam, leading to AmpC overproduction and the consequent emergence of resistance to 3GCs and piperacillin/tazobactam during treatment. Because of this phenomenon, the use of carbapenems or cefepime is considered a safer option when treating these pathogens. However, many areas of uncertainty persist, including the risk of derepression related to each beta-lactam; the role of piperacillin/tazobactam compared to cefepime; the best option for severe or difficult-to-treat cases, such as high-inoculum infections (e.g., ventilator-associated pneumonia and undrainable abscesses); the role of de-escalation once clinical stability is obtained; and the best treatment for species with a lower risk of derepression during treatment (e.g., Serratia marcescens and Morganella morganii). The aim of this review is to collate the most relevant information about the microbiological properties of and therapeutic approach to AmpC-producing Enterobacterales in order to inform daily clinical practice. [ABSTRACT FROM AUTHOR]

Background: Environmental reservoirs of antibiotic resistance pose a threat to human and animal health. Aquatic biofilms impacted by wastewater effluent (WW) are known environmental reservoirs for antibiotic resistance; however, the relative importance of biotic factors and abiotic factors from WW on the abundance of antibiotic resistance genes (ARGs) within aquatic biofilms remains unclear. Additionally, experimental evidence is limited within complex aquatic microbial communities as to whether genes bearing low sequence similarity to validated reference ARGs are functional as ARGs. Results: To disentangle the effects of abiotic and biotic factors on ARG abundances, natural biofilms were previously grown in flume systems with different proportions of stream water and either ultrafiltered or non-ultrafiltered WW. In this study, we conducted deep shotgun metagenomic sequencing of 75 biofilm, stream, and WW samples from these flume systems and compared the taxonomic and functional microbiome and resistome composition. Statistical analysis revealed an alignment of the resistome and microbiome composition and a significant association with experimental treatment. Several ARG classes exhibited an increase in normalized metagenomic abundances in biofilms grown with increasing percentages of non-ultrafiltered WW. In contrast, sulfonamide and extended-spectrum beta-lactamase ARGs showed greater abundances in biofilms grown in ultrafiltered WW compared to non-ultrafiltered WW. Overall, our results pointed toward the dominance of biotic factors over abiotic factors in determining ARG abundances in WW-impacted stream biofilms and suggested gene family-specific mechanisms for ARGs that exhibited divergent abundance patterns. To investigate one of these specific ARG families experimentally, we biochemically characterized a new beta-lactamase from the Planctomycetota (Phycisphaeraceae). This beta-lactamase displayed activity in the cleavage of cephalosporin analog despite sharing a low sequence identity with known ARGs. Conclusions: This discovery of a functional planctomycete beta-lactamase ARG is noteworthy, not only because it was the first beta-lactamase to be biochemically characterized from this phylum, but also because it was not detected by standard homology-based ARG tools. In summary, this study conducted a metagenomic analysis of the relative importance of biotic and abiotic factors in the context of WW discharge and their impact on both known and new ARGs in aquatic biofilms. DkJa1T-YWptaXXeH_hsDtB Video Abstract [ABSTRACT FROM AUTHOR]

We describe a case of New Delhi metallo-β-lactamase 1-producing carbapenem-resistant Pseudomonas aeruginosa (CRPA) in a transplant patient with multiple hospitalizations in California, USA. Whole-genome sequencing revealed the isolate was genetically distinctive, despite ≈95% similarity to other global strains. The patient's lack of international travel suggests this CRPA was acquired domestically.

Carbapenem-resistant Acinetobacter baumannii (CRAb) is an urgent public health threat, according to the CDC. This pathogen has few treatment options and causes severe nosocomial infections with > 50% fatality rate. Although previous studies have examined the proteome of CRAb, there have been no focused analyses of dynamic changes to β-lactamase expression that may occur due to drug exposure. Here, we present our initial proteomic study of variation in β-lactamase expression that occurs in CRAb with different β-lactam antibiotics. Briefly, drug resistance to Ab (ATCC 19606) was induced by the administration of various classes of β-lactam antibiotics, and the cell-free supernatant was isolated, concentrated, separated by SDS-PAGE, digested with trypsin, and identified by label-free LC-MS-based quantitative proteomics. Thirteen proteins were identified and evaluated using a 1789 sequence database of Ab β-lactamases from UniProt, the majority of which were Class C β-lactamases (≥ 80%). Importantly, different antibiotics, even those of the same class (e.g. penicillin and amoxicillin), induced non-equivalent responses comprising various isoforms of Class C and D serine-β-lactamases, resulting in unique resistomes. These results open the door to a new approach of analyzing and studying the problem of multi-drug resistance in bacteria that rely strongly on β-lactamase expression.

ABSTRACT Pseudomonas aeruginosa is a highly problematic opportunistic pathogen that causes a range of different infections. Infections are commonly treated with β-lactam antibiotics, including cephalosporins, monobactams, penicillins, and carbapenems, with carbapenems regarded as antibiotics of last resort. Isolates of P. aeruginosa can contain horizontally acquired bla genes encoding β-lactamase enzymes, but the extent to which these contribute to β-lactam resistance in this species has not been systematically quantified. The overall aim of this research was to address this knowledge gap by quantifying the frequency of β-lactamase-encoding genes in P. aeruginosa and by determining the effects of β-lactamases on susceptibility of P. aeruginosa to β-lactams. Genome analysis showed that β-lactamase-encoding genes are present in 3% of P. aeruginosa but are enriched in carbapenem-resistant isolates (35%). To determine the substrate antibiotics, 10 β-lactamases were expressed from an integrative plasmid in the chromosome of P. aeruginosa reference strain PAO1. The β-lactamases reduced susceptibility to a variety of clinically used antibiotics, including carbapenems (meropenem, imipenem), penicillins (ticarcillin, piperacillin), cephalosporins (ceftazidime, cefepime), and a monobactam (aztreonam). Different enzymes acted on different β-lactams. β-lactamases encoded by the genomes of P. aeruginosa clinical isolates had similar effects to the enzymes expressed in strain PAO1. Genome engineering was used to delete β-lactamase-encoding genes from three carbapenem-resistant clinical isolates and increased susceptibility to substrate β-lactams. Our findings demonstrate that acquired β-lactamases play an important role in β-lactam resistance in P. aeruginosa, identifying substrate antibiotics for a range of enzymes and quantifying their contributions to resistance.IMPORTANCEPseudomonas aeruginosa is an extremely problematic pathogen, with isolates that are resistant to the carbapenem class of β-lactam antibiotics being in critical need of new therapies. Genes encoding β-lactamase enzymes that degrade β-lactam antibiotics can be present in P. aeruginosa, including carbapenem-resistant isolates. Here, we show that β-lactamase genes are over-represented in carbapenem-resistant isolates, indicating their key role in resistance. We also show that different β-lactamases alter susceptibility of P. aeruginosa to different β-lactam antibiotics and quantify the effects of selected enzymes on β-lactam susceptibility. This research significantly advances the understanding of the contributions of acquired β-lactamases to antibiotic resistance, including carbapenem resistance, in P. aeruginosa and by implication in other species. It has potential to expedite development of methods that use whole genome sequencing of infecting bacteria to inform antibiotic treatment, allowing more effective use of antibiotics, and facilitate the development of new antibiotics.

This study aimed to identify and evaluate the antimicrobial susceptibility profile of extended-spectrum β-lactamase (ESBL)-producing Enterobacterales isolated from blood cultures of patients with suspected sepsis. This retrospective cross-sectional epidemiological study was performed for four years (2015 to 2018) by accessing the medical records of patients diagnosed with bloodstream infections in two tertiary public hospitals in Brazil. Culture results and susceptibility tests of bacterial strains isolated from blood samples were analyzed. During four years, 2,263 blood culture exams were performed, and Enterobacterales were isolated in 694 (30.7%) samples. The disk approximation test detected ESBL production in 171 (24.6%) of the 694 isolated Enterobacterales (p

While most detailed analyses of antibiotic resistance plasmids focus on those found in clinical isolates, less is known about the vast environmental reservoir of mobile genetic elements and the resistance and virulence factors they encode. We selectively isolated three strains of cefotaxime-resistant Escherichia coli from a wastewater-impacted coastal wetland. The cefotaxime-resistant phenotype was transmissible to a lab strain of E. coli after one hour, with frequencies as high as 10-3 transconjugants per recipient. Two of the plasmids also transferred cefotaxime resistance to Pseudomonas putida, but these were unable to back-transfer this resistance from P. putida to E. coli. In addition to the cephalosporins, E. coli transconjugants inherited resistance to at least seven distinct classes of antibiotics. Complete nucleotide sequences revealed large IncF-type plasmids with globally distributed replicon sequence types F31:A4:B1 and F18:B1:C4 carrying diverse antibiotic resistance and virulence genes. The plasmids encoded extended-spectrum β-lactamases blaCTX-M-15 or blaCTX-M-55, each associated with the insertion sequence ISEc9, although in different local arrangements. Despite similar resistance profiles, the plasmids shared only one resistance gene in common, the aminoglycoside acetyltransferase aac(3)-IIe. Plasmid accessory cargo also included virulence factors involved in iron acquisition and defense against host immunity. Despite their sequence similarities, several large-scale recombination events were detected, including rearrangements and inversions. In conclusion, selection with a single antibiotic, cefotaxime, yielded conjugative plasmids conferring multiple resistance and virulence factors. Clearly, efforts to limit the spread of antibiotic resistance and virulence among bacteria must include a greater understanding of mobile elements in the natural and human-impacted environments.

Recurrent urinary tract infections (rUTI) are common in kidney transplant recipients (KTR) and are associated with multidrug resistance and increased morbidity/mortality. Novel antibiotic alternatives to reduce UTI recurrence are critically needed. We describe a case of rUTI due to extended spectrum beta lactamase (ESBL) Klebsiella pneumoniae in a KTR that was treated successfully with 4 weeks of adjunctive intravenous bacteriophage therapy alone, without concomitant antibiotics, and with no recurrence in a year of follow-up.

BackgroundThe role of piperacillin/tazobactam for treatment of serious infections due to AmpC-producing organisms remains debatable, particularly in immunocompromised patients.MethodsThis was a retrospective cohort study in immunocompromised patients that investigated the effect of definitive treatment with either piperacillin/tazobactam versus cefepime or carbapenems for bacteraemia caused by cefoxitin-non-susceptible Enterobacterales. The primary endpoint was a composite of clinical and microbiological failure. A logistic regression model was constructed to assess the impact of definitive treatment choice on the primary endpoint.ResultsA total of 81 immunocompromised patients with blood cultures positive for cefoxitin-non-susceptible Enterobacterales were included for analysis. There was more microbiological failure in the piperacillin/tazobactam arm compared with the cefepime/carbapenem arm (11.4% versus 0.0%, P = 0.019). Definitive treatment with cefepime or a carbapenem was associated with a decreased odds of clinical or microbiological failure (OR 0.303, 95% CI 0.093-0.991, P = 0.048) when controlling for baseline characteristics.ConclusionsIn immunocompromised patients with bacteraemia due to cefoxitin-non-susceptible Enterobacterales, definitive treatment with piperacillin/tazobactam was associated with an increased risk of microbiological failure and higher odds of clinical or microbiological failure compared with cefepime or carbapenems.

Food contamination with pathogenic Escherichia coli can cause severe disease. Here, we report the isolation of a multidrug resistant strain (A23EC) from fresh spinach. A23EC belongs to subclade C2 of ST131, a virulent clone of Extraintestinal Pathogenic E. coli (ExPEC). Most A23EC virulence factors are concentrated in three pathogenicity islands. These include PapGII, a fimbrial tip adhesin linked to increased virulence, and CsgA and CsgB, two adhesins known to facilitate spinach leaf colonization. A23EC also bears TnMB1860, a chromosomally-integrated transposon with the demonstrated potential to facilitate the evolution of carbapenem resistance among non-carbapenemase-producing enterobacterales. This transposon consists of two IS26-bound modular translocatable units (TUs). The first TU carries aac(6)-lb-cr, bla OXA-1, ΔcatB3, aac(3)-lle, and tmrB, and the second one harbors bla CXT-M-15. A23EC also bears a self-transmissible plasmid that can mediate conjugation at 20°C and that has a mosaic IncF [F(31,36):A(4,20):B1] and Col156 origin of replication. Comparing A23EC to 86 additional complete ST131 sequences, A23EC forms a monophyletic cluster with 17 other strains that share the following four genomic traits: (1) virotype E (papGII+); (2) presence of a PAI II536-like pathogenicity island with an additional cnf1 gene; (3) presence of chromosomal TnMB1860; and (4) frequent presence of an F(31,36):A(4,20):B1 plasmid. Sequences belonging to this cluster (which we named C2b sublineage) are highly enriched in septicemia samples and their associated genetic markers align with recent reports of an emerging, virulent sublineage of the C2 subclade, suggesting significant pathogenic potential. This is the first report of a ST131 strain belonging to subclade C2 contaminating green leafy vegetables. The detection of this uropathogenic clone in fresh food is alarming. This work suggests that ST131 continues to evolve, gaining selective advantages and new routes of transmission. This highlights the pressing need for rigorous epidemiological surveillance of ExPEC in vegetables with One Health perspective.

BackgroundUrinary tract infections caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (ESBL-E. coli) may occur as outbreaks due to common-source exposures. Yet, it is currently unknown if they cluster geographically as would be expected as part of an outbreak.MethodsWe collected electronic health record data on all patients living in San Francisco with culture-documented community-onset E. coli bacteriuria in a safety-net public healthcare system from January 2014 to March 2020 (diagnosed

BackgroundAntimicrobial resistant infections continue to be a leading global public health crisis. Mobile genetic elements, such as plasmids, have been shown to play a major role in the dissemination of antimicrobial resistance (AMR) genes. Despite its ongoing threat to human health, surveillance of AMR in the United States is often limited to phenotypic resistance. Genomic analyses are important to better understand the underlying resistance mechanisms, assess risk, and implement appropriate prevention strategies. This study aimed to investigate the extent of plasmid mediated antimicrobial resistance that can be inferred from short read sequences of carbapenem resistant E. coli (CR-Ec) in Alameda County, California. E. coli isolates from healthcare locations in Alameda County were sequenced using an Illumina MiSeq and assembled with Unicycler. Genomes were categorized according to predefined multilocus sequence typing (MLST) and core genome multilocus sequence typing (cgMLST) schemes. Resistance genes were identified and corresponding contigs were predicted to be plasmid-borne or chromosome-borne using two bioinformatic tools (MOB-suite and mlplasmids).ResultsAmong 82 of CR-Ec identified between 2017 and 2019, twenty-five sequence types (STs) were detected. ST131 was the most prominent (n = 17) followed closely by ST405 (n = 12). blaCTX-M were the most common ESBL genes and just over half (18/30) of these genes were predicted to be plasmid-borne by both MOB-suite and mlplasmids. Three genetically related groups of E. coli isolates were identified with cgMLST. One of the groups contained an isolate with a chromosome-borne blaCTX-M-15 gene and an isolate with a plasmid-borne blaCTX-M-15 gene.ConclusionsThis study provides insights into the dominant clonal groups driving carbapenem resistant E. coli infections in Alameda County, CA, USA clinical sites and highlights the relevance of whole-genome sequencing in routine local genomic surveillance. The finding of multi-drug resistant plasmids harboring high-risk resistance genes is of concern as it indicates a risk of dissemination to previously susceptible clonal groups, potentially complicating clinical and public health intervention.

CTX-M β-lactamases are prevalent antibiotic resistance enzymes and are notable for their ability to rapidly hydrolyze the extended-spectrum cephalosporin, cefotaxime. We hypothesized that the active site sequence requirements of CTX-M-mediated hydrolysis differ between classes of β-lactam antibiotics. Accordingly, we use codon randomization, antibiotic selection, and deep sequencing to determine the CTX-M active-site residues required for hydrolysis of cefotaxime and the penicillin, ampicillin. The study reveals positions required for hydrolysis of all β-lactams, as well as residues controlling substrate specificity. Further, CTX-M enzymes poorly hydrolyze the extended-spectrum cephalosporin, ceftazidime. We further show that the sequence requirements for ceftazidime hydrolysis follow those of cefotaxime, with the exception that key active-site omega loop residues are not required, and may be detrimental, for ceftazidime hydrolysis. These results provide insights into cephalosporin hydrolysis and demonstrate that changes to the active-site omega loop are likely required for the evolution of CTX-M-mediated ceftazidime resistance.

Multiple mutations often have non-additive (epistatic) phenotypic effects. Epistasis is of fundamental biological relevance but is not well understood mechanistically. Adaptive evolution, i.e., the evolution of new biochemical activities, is rich in epistatic interactions. To better understand the principles underlying epistasis during genetic adaptation, we studied the evolution of TEM-1 β-lactamase variants exhibiting cefotaxime resistance. We report the collection of a library of 487 observed evolutionary trajectories for TEM-1 and determine the epistasis status based on cefotaxime resistance phenotype for 206 combinations of 2-3 TEM-1 mutations involving 17 positions under adaptive selective pressure. Gain-of-function (GOF) mutations are gatekeepers for adaptation. To see if GOF phenotypes can be inferred based solely on sequence data, we calculated the enrichment of GOF mutations in the different categories of epistatic pairs. Our results suggest that this is possible because GOF mutations are particularly enriched in sign and reciprocal sign epistasis, which leave a major imprint on the sequence space accessible to evolution. We also used FoldX to explore the relationship between thermodynamic stability and epistasis. We found that mutations in observed evolutionary trajectories tend to destabilize the folded structure of the protein, albeit their cumulative effects are consistently below the protein's free energy of folding. The destabilizing effect is stronger for epistatic pairs, suggesting that modest or local alterations in folding stability can modulate catalysis. Finally, we report a significant relationship between epistasis and the degree to which two protein positions are structurally and dynamically coupled, even in the absence of ligand.

Antimicrobial resistance in urinary tract infections (UTIs) is a major public health concern. This study aims to characterize the phenotypic and genetic basis of multidrug resistance (MDR) among expanded-spectrum cephalosporin-resistant (ESCR) uropathogenic Escherichia coli (UPEC) causing UTIs in California patient populations. Between February and October 2019, 577 ESCR UPEC isolates were collected from patients at 6 clinical laboratory sites across California. Lineage and antibiotic resistance genes were determined by analysis of whole-genome sequence data. The lineages ST131, ST1193, ST648, and ST69 were predominant, representing 46%, 5.5%, 4.5%, and 4.5% of the collection, respectively. Overall, 527 (91%) isolates had an expanded-spectrum β-lactamase (ESBL) phenotype, with blaCTX-M-15, blaCTX-M-27, blaCTX-M-55, and blaCTX-M-14 being the most prevalent ESBL genes. In the 50 non-ESBL phenotype isolates, 40 (62%) contained blaCMY-2, which was the predominant plasmid-mediated AmpC (pAmpC) gene. Narrow-spectrum β-lactamases, blaTEM-1B and blaOXA-1, were also found in 44.9% and 32.1% of isolates, respectively. Among ESCR UPEC isolates, isolates with an ESBL phenotype had a 1.7-times-greater likelihood of being MDR than non-ESBL phenotype isolates (P < 0.001). The cooccurrence of blaCTX-M-15, blaOXA-1, and aac(6')-Ib-cr within ESCR UPEC isolates was strongly correlated. Cooccurrence of blaCTX-M-15, blaOXA-1, and aac(6')-Ib-cr was associated with an increased risk of nonsusceptibility to piperacillin-tazobactam, cefepime, fluoroquinolones, and amikacin as well as MDR. Multivariate regression revealed the presence of blaCTX-M-55, blaTEM-1B, and the ST131 genotype as predictors of MDR. IMPORTANCE The rising incidence of resistance to expanded-spectrum cephalosporins among Escherichia coli strains, the most common cause of UTIs, is threatening our ability to successfully empirically treat these infections. ESCR E. coli strains are often MDR; therefore, UTI caused by these organisms often leads to treatment failure, increased length of hospital stay, and severe complications (D. G. Mark, Y.-Y. Hung, Z. Salim, N. J. Tarlton, et al., Ann Emerg Med 78:357-369, 2021, https://doi.org/10.1016/j.annemergmed.2021.01.003). Here, we performed an in-depth analysis of genetic factors of ESCR E. coli associated with coresistance and MDR. Such knowledge is critical to advance UTI diagnosis, treatment, and antibiotic stewardship.

The success of the discovery and development of antimicrobials is a milestone in modern medicine since it is considered that there is a before and after the beginning of the clinical use of antibiotics in the treatment of infectious diseases. Antibiotic treatment has had a great impact in reducing morbidity and mortality caused by infections that can be treated, reducing the duration of illness and the potential serious complications that could arise. However, since the beginning of the clinical use of antibiotics at the end of the first half of the 20th century, it was identified that there was specificity of antibiotics to perform their action against different bacteria naturally (intrinsic resistance) and even more so, that bacteria that by species were previously sensitive to the effect of an antibiotic, over time they appeared resistant to them (acquired resistance). [ABSTRACT FROM AUTHOR]

ObjectivesTo evaluate the in vitro antimicrobial susceptibilities of Gram-positive and Gram-negative isolates from patients in Jordan between 2010 and 2021, through the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme.MethodsMedical centres in Jordan collected bacterial isolates from hospitalised patients with defined infection sources between 2010 and 2021 (no isolates collected in 2014). Antimicrobial susceptibility was interpreted using CLSI standards. FDA-approved breakpoints were applied for tigecycline. The identification of β-lactamase genes was performed for a proportion of isolates using multiplex PCR assays.ResultsMore than 92% of Acinetobacter baumannii collected were multidrug-resistant (MDR) and/or carbapenem-resistant (CR), and > 50% susceptibility was reported only to minocycline (62.2% among both MDR and CR isolates). Rates of MDR and CR Pseudomonas aeruginosa were 14.3% and 20.5%, respectively, and among all P. aeruginosa collected from adults, susceptibility to ceftazidime/avibactam was 95.3% and to ceftolozane/tazobactam was 88.4%. For Escherichia coli from adults and MDR E. coli, susceptibility to ceftazidime/avibactam, ceftolozane/tazobactam, imipenem, meropenem and meropenem/vaborbactam was 92.1%–98.7%. Susceptibility to tigecycline was > 94% among Klebsiella pneumoniae from adult, paediatric, and ICU patients (all ages). CTX-M-15 was the most frequently identified β-lactamase gene among E. coli and K. pneumoniae. Susceptibility to most antimicrobial agents was < 50% among K. pneumoniae carrying CTX-M-15, CTX-M-9-type, NDM-5, and/or OXA-48 β-lactamase genes. All S. aureus collected were susceptible to teicoplanin, vancomycin, daptomycin, linezolid and tigecycline, with 96.1% of S. aureus from adults were susceptible to ceftaroline. Overall, 58.8% of Staphylococcus aureus were MRSA.ConclusionThis study provides valuable information regarding antimicrobial susceptibility in Jordan between 2010 and 2021. Continued monitoring of in vitro antimicrobial susceptibility is critical in the fight against antimicrobial resistance.

ABSTRACT Pseudomonas aeruginosa encodes the beta-lactamase AmpC, which promotes resistance to beta-lactam antibiotics. Expression of ampC is induced by anhydro-muropeptides (AMPs) released from the peptidoglycan (PG) cell wall upon beta-lactam treatment. AmpC can also be induced via genetic inactivation of PG biogenesis factors such as the endopeptidase DacB that cleaves PG crosslinks. Mutants in dacB occur in beta-lactam-resistant clinical isolates of P. aeruginosa, but it has remained unclear why DacB inactivation promotes ampC induction. Similarly, the inactivation of lytic transglycosylase (LT) enzymes such as SltB1 that cut PG glycans has also been associated with ampC induction and beta-lactam resistance. Given that LT enzymes are capable of producing AMP products that serve as ampC inducers, this latter observation has been especially difficult to explain. Here, we show that ampC induction in sltB1 or dacB mutants requires another LT enzyme called MltG. In Escherichia coli, MltG has been implicated in the degradation of nascent PG strands produced upon beta-lactam treatment. Accordingly, in P. aeruginosa sltB1 and dacB mutants, we detected the MltG-dependent production of pentapeptide-containing AMP products that are signatures of nascent PG degradation. Our results therefore support a model in which SltB1 and DacB use their PG-cleaving activity to open space in the PG matrix for the insertion of new material. Thus, their inactivation mimics low-level beta-lactam treatment by reducing the efficiency of new PG insertion into the wall, causing the degradation of some nascent PG material by MltG to produce the ampC-inducing signal.IMPORTANCEInducible beta-lactamases like the ampC system of Pseudomonas aeruginosa are a common determinant of beta-lactam resistance among gram-negative bacteria. The regulation of ampC is elegantly tuned to detect defects in cell wall synthesis caused by beta-lactam drugs. Studies of mutations causing ampC induction in the absence of drug therefore promise to reveal new insights into the process of cell wall biogenesis in addition to aiding our understanding of how resistance to beta-lactam antibiotics arises in the clinic. In this study, the ampC induction phenotype for mutants lacking a glycan-cleaving enzyme or an enzyme that cuts cell wall crosslinks was used to uncover a potential role for these enzymes in making space in the wall matrix for the insertion of new material during cell growth.

Background To limit the use of antimicrobials without disincentivising the development of novel antimicrobials, there is interest in establishing innovative models that fund antimicrobials based on an evaluation of their value as opposed to the volumes used. The aim of this project was to evaluate the population-level health benefit of cefiderocol in the NHS in England, for the treatment of severe aerobic Gram-negative bacterial infections when used within its licensed indications. The results were used to inform the National Institute for Health and Care Excellence guidance in support of commercial discussions regarding contract value between the manufacturer and NHS England. Methods The health benefit of cefiderocol was first derived for a series of high-value clinical scenarios. These represented uses that were expected to have a significant impact on patients’ mortality risks and health-related quality of life. The clinical effectiveness of cefiderocol relative to its comparators was estimated by synthesising evidence on susceptibility of the pathogens of interest to the antimicrobials in a network meta-analysis. Patient-level costs and health outcomes of cefiderocol under various usage scenarios compared with alternative management strategies were quantified using decision modelling. Results were reported as incremental net health effects expressed in quality-adjusted life-years, which were scaled to 20-year population values using infection number forecasts based on data from Public Health England. The outcomes estimated for the high-value clinical scenarios were extrapolated to other expected uses for cefiderocol. Results Among Enterobacterales isolates with the metallo-beta-lactamase resistance mechanism, the base-case network meta-analysis found that cefiderocol was associated with a lower susceptibility relative to colistin (odds ratio 0.32, 95% credible intervals 0.04 to 2.47), but the result was not statistically significant. The other treatments were also associated with lower susceptibility than colistin, but the results were not statistically significant. In the metallo-beta-lactamase Pseudomonas aeruginosa base-case network meta-analysis, cefiderocol was associated with a lower susceptibility relative to colistin (odds ratio 0.44, 95% credible intervals 0.03 to 3.94), but the result was not statistically significant. The other treatments were associated with no susceptibility. In the base case, patient-level benefit of cefiderocol was between 0.02 and 0.15 quality-adjusted life-years, depending on the site of infection, the pathogen and the usage scenario. There was a high degree of uncertainty surrounding the benefits of cefiderocol across all subgroups. There was substantial uncertainty in the number of infections that are suitable for treatment with cefiderocol, so population-level results are presented for a range of scenarios for the current infection numbers, the expected increases in infections over time and rates of emergence of resistance. The population-level benefits varied substantially across the base-case scenarios, from 896 to 3559 quality-adjusted life-years over 20 years. Conclusion This work has provided quantitative estimates of the value of cefiderocol within its areas of expected usage within the NHS. Limitations Given existing evidence, the estimates of the value of cefiderocol are highly uncertain. Future work Future evaluations of antimicrobials would benefit from improvements to NHS data linkages; research to support appropriate synthesis of susceptibility studies; and application of routine data and decision modelling to assess enablement value. Study registration No registration of this study was undertaken. Funding This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment Policy Research Programme (NIHR award ref: NIHR135591), conducted through the Policy Research Unit in Economic Methods of Evaluation in Health and Social Care Interventions, PR-PRU-1217-20401, and is published in full in Health Technology Assessment; Vol. 28, No. 28. See the NIHR Funding and Awards website for further award information. Plain language summary This project tested new methods for estimating the value to the NHS of an antimicrobial, cefiderocol, so its manufacturer could be paid fairly even if very little drug is used in order to reduce the risk of bacteria becoming resistant to the product. Clinicians said that the greatest benefit of cefiderocol is when used for complicated urinary tract infections and pneumonia acquired within hospitals caused by two types of bacteria (called Enterobacterales and Pseudomonas aeruginosa), with a resistance mechanism called metallo-beta-lactamase. Because there were no relevant clinical trial data, we estimated how effective cefiderocol and alternative treatments were by doing a systematic literature review of studies that grew bacteria from infections in the laboratory and tested the drugs on them. We linked this to data estimating the long-term health and survival of patients. Some evidence was obtained by asking clinicians detailed questions about what they thought the effects would be based on their experience and the available evidence. We included the side effects of the alternative treatments, some of which can cause kidney damage. We estimated how many infections there would be in the UK, whether they would increase over time and how resistance to treatments may change over time. Clinicians told us that they would also use cefiderocol to treat intra-abdominal and bloodstream infections, and some infections caused by another bacteria called Stenotrophomonas. We estimated how many of these infections there would be, and assumed the same health benefits as for other types of infections. The total value to the NHS was calculated using these estimates. We also considered whether we had missed any additional elements of value. We estimated that the value to the NHS was £18–71 million over 20 years. This reflects the maximum the NHS could pay for use of cefiderocol if the health lost as a result of making these payments rather than funding other NHS services is not to exceed the health benefits of using this antimicrobial. However, these estimates are uncertain due to limitations with the evidence used to produce them and assumptions that had to be made. Scientific summary This section reproduces and adapts, with permission, content previously published as part of the study protocol (Harnan SE, Woods B, Schmitt L, Kearns B, Srivastava T, Scope A, et al. Protocol for the technology evaluation of cefiderocol for treating severe aerobic Gram-negative bacterial infections. Health Technol Assess 2021.) Background The National Institute for Health and Care Excellence (NICE), NHS England and NHS Improvement are currently undertaking a project to assess the feasibility of innovative models that pay for antimicrobials (AMs) based on an evaluation of their value to the NHS as opposed to the volumes used. This project involves evaluation of two AMs to inform commercial discussions regarding contract value for a period of up to 10 years. This report details the evaluation phase of this project for cefiderocol (Fetcroja), which is manufactured by Shionogi. Cefiderocol is an injectable siderophore cephalosporin and received a marketing authorisation in April 2020 for treating infections due to aerobic Gram-negative organisms in adults with limited treatment options. Aim and objectives The aim of this evaluation is to assess the value of cefiderocol to the NHS in England when used within its licensed indications. Specific objectives are: To identify two high-value clinical scenarios (HVCSs), within its broad licensed indications, for which cefiderocol is expected to have a significant impact on patients’ outcomes in terms of reducing mortality risks and improving health-related quality of life (HRQoL). To undertake an ‘evidence mapping’ exercise and relevant systematic literature reviews to characterise the available clinical effectiveness evidence for the use of cefiderocol in the HVCSs. To establish an appropriate decision-analytic model to quantify the costs and health benefits of the use of cefiderocol under various usage scenarios compared with usage scenarios involving other available AMs in the HVCSs. The decision-analytic model was required to estimate costs and health effects at both the individual level and the aggregate population level, providing population-level incremental net health effects (INHEs). Drawing on the systematic reviews and evidence synthesis, national-level data on healthcare-associated infections and other sources as needed, to identify evidence to populate the decision-analytic models. To use structured expert elicitation as necessary to supplement the available evidence to populate the decision-analytic models. To use available evidence and, where necessary, expert opinion quantitatively to extrapolate estimated population-level INHEs associated with cefiderocol in the HVCSs to other expected uses for the product within the product’s licensed indications. Expected usage and high-value clinical scenarios The licensed indication for cefiderocol is broad. In practice, to control the spread of resistance to cefiderocol and to preserve its long-term viability as an effective treatment option against highly resistant pathogens, cefiderocol may be used in a more restricted group of patients than permitted by its license. Quantifying the health and cost implications of using cefiderocol across anticipated NHS usage, even within this restricted population, remains challenging, as the use is expected in infections which differ in causative organism (pathogen, resistance mechanism), site of the infection, healthcare setting and other patient characteristics. This evaluation characterises the value of cefiderocol across its range of expected uses via a two-step approach. First, decision modelling is used quantitatively to assess the value of cefiderocol in a set of scenarios defined by features of the pathogen, site of infection, healthcare setting and other patient characteristics, considered to represent important uses of cefiderocol; referred to as the HVCSs. Second, rescaling is used to estimate how this evidence can be used to provide quantitative assessments of value in the overall population expected to receive cefiderocol, including patients who fall outside the HVCSs but who are relevant to determining the overall value of cefiderocol to the English NHS. The HVCSs were selected to reflect areas of clinical use where there is a current significant burden from resistant infections, and cefiderocol is expected to offer significant improvements over existing treatments in terms of efficacy and/or safety. The HVCSs were selected based on feedback from the manufacturer, clinical advisors to the Policy Research Unit in Economic Methods of Evaluation in Health and Social Care Interventions (EEPRU) and broader stakeholders involved in the NICE scoping process. The HVCSs focus on the following patient populations: Empiric setting (ES): patients with an infection strongly suspected to be caused by metallo-beta-lactamase (MBL)-producing Enterobacterales or MBL-producing Pseudomonas aeruginosa in patients with hospital-acquired pneumonia or ventilator-associated pneumonia (HAP/VAP). In this patient group, the pathogen, resistance mechanism and antibiotic susceptibility have not yet been established, but treatment is initiated immediately due to the severity of the infection. Microbiology-directed setting (MDS): patients with an infection confirmed to be caused by MBL Enterobacterales or MBL P. aeruginosa, where antibiotic susceptibility testing results are available, and where the site of infection is HAP/VAP or complicated urinary tract infection (cUTI). The resourcing for this project was equivalent to that of a diagnostic assessment review or multiple technology assessment for NICE, but the levels of analysis extend from the typical focus of those evaluations on a single type of patient for one indication and setting. In this evaluation, we also include population-level health effects now and over time, and across several indications and settings. The objective is to use appropriate analyses of the available evidence at every level, but the detail in those analyses is inevitably constrained by the time and resources available for the project. Clinical evidence Methods There are evidential challenges when evaluating the use of new or nearly new AMs to treat infections caused by multidrug-resistant (MDR) pathogens. Randomised controlled trials (RCTs) are of generally low relevance as they tend not to recruit patients with MDR pathogens. Therefore, relative treatment effects between the intervention and comparator cannot be generalised to MDR pathogens, as this may overestimate the efficacy of the comparator. It was anticipated that RCTs were unlikely to be the primary source of evidence. Therefore, a mapping review was undertaken to establish available evidence and ascertain which approach to estimating comparative effectiveness could inform an economic model. Reviews 1 and 2 considered RCTs and observational studies of cefiderocol in patients with HAP/VAP or cUTI infections caused by MBL Enterobacterales or P. aeruginosa or suspected to be caused by carbapenem-resistant Enterobacterales or P. aeruginosa. In Review 3, in vitro susceptibility studies were considered. These studies provide evidence on the proportion of isolates that are susceptible to treatments and comparators as an indication of relative efficacy. Susceptibility studies were considered eligible if they reported susceptibility for MBL Enterobacterales or P. aeruginosa isolates, from any infection site (clinical advisors indicated that infection site was not associated with susceptibility profile), and reported susceptibility to cefiderocol and at least one comparator as defined by the HVCSs (colistin, meropenem, tigecycline, aztreonam, fosfomycin, gentamicin, amikacin, tobramycin). Susceptibility studies test isolates in vitro to ascertain the minimum concentration of any given treatment that is needed to inhibit growth of the microbe [the minimum inhibitory concentration (MIC)]. If this is below the clinical breakpoint published by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) [or by the Clinical Laboratory Standards Institute (CLSI) from the USA], the isolate is considered susceptible, and is likely to respond to treatment in vivo. In the UK, the British Society for Antimicrobial Chemotherapy (BSAC) recommends use of EUCAST guidelines. Systematic searches across relevant databases [MEDLINE, EMBASE and Centre for Review and Dissemination (CRD) database] were conducted in March 2021. EEPRU also considered evidence submitted by Shionogi and Public Health England (PHE). After mapping, only Review 3 was pursued, since there was insufficient evidence from Reviews 1 and 2. Risk of bias assessment was performed using a bespoke tool developed for this evaluation. No studies of fosfomycin were identified. An additional rapid review was conducted to identify studies reporting the susceptibility of fosfomycin and at least one other HVCS comparator. A random-effects network meta-analysis (NMA) of susceptibility studies was conducted to allow a comprehensive synthesis of evidence on all relevant treatments. A different network was constructed for each subgroup of pathogens (MBL Enterobacterales and MBL P. aeruginosa), since susceptibility profiles were expected to differ. For each of these, a network was constructed using EUCAST breakpoints and another using CLSI breakpoints. The EUCAST networks were considered the main analysis, while the CLSI networks were considered in sensitivity analyses. Sensitivity analyses were also conducted to test assumptions around the inclusion of comparators in the network, to assess the impact of missed data on the analysis, and prioritising PHE data where possible as these are from English isolates and, therefore, have the highest relevance. Two additional reviews were conducted to provide evidence on the link between susceptibility and clinical outcomes (Review 4) and between susceptibility and long-term outcomes (Review 5) in the sites of interest. A further review (Review 6) was conducted to identify any important safety implications of cefiderocol. Results The reviews of RCT and observational studies identified insufficient evidence to inform an assessment of clinical effectiveness. One RCT did report subgroup data relating to MBLs, but the subgroup was small (n = 16 in the cefiderocol arm, n = 7 in the best available therapy arm) and was, therefore, not used due to the chance of baseline imbalances introducing bias. The key limitations of the observational studies that were identified included small numbers of MBL infections (range n = 2–17 patients), high levels of heterogeneity with respect to prognostic factors, and data not being reported for the sites of interest. Review 3 identified in vitro susceptibility studies in relatively large samples of MBL Enterobacterales or P. aeruginosa isolates obtained from a range of clinical sites of infection. Three studies (SIDERO CR, SIDERO WT and Johnston et al.) reporting data for cefiderocol and at least one comparator met the inclusion criteria and were synthesised. The separate review of fosfomycin identified 10 studies. In the MBL Enterobacterales EUCAST analysis, cefiderocol was associated with a lower susceptibility relative to colistin [odds ratio (OR) 0.32, 95% credible intervals (CrI) 0.04 to 2.47], but the result was not statistically significant. Fosfomycin had a similar OR (OR 0.34, 95% CrI 0.06 to 1.96) compared to colistin as cefiderocol. The remainder of the treatments were also associated with lower susceptibility than colistin, but the results were not statistically significant. In the MBL P. aeruginosa EUCAST analysis, cefiderocol was associated with a lower susceptibility relative to colistin (OR 0.44, 95% CrI 0.03 to 3.94), but the result was not statistically significant. The remainder of the treatments were associated with no susceptibility. Heterogeneity was high in both networks. In the sensitivity analyses using CLSI breakpoints, where the breakpoint for cefiderocol is higher, cefiderocol was associated with a higher susceptibility relative to colistin. However, the results were very uncertain in some of the NMAs due to sparse data and a large number of treatment arms with either zero or 100% susceptibility. Review 4 (link between susceptibility and clinical outcomes) identified two studies that reported mortality or hospital length of stay (LoS) conditional on susceptibility to empiric treatment and were selected for use in the model for the ES. No useful evidence relating to the MDS was identified. Review 5 (link between susceptibility and long-term clinical outcomes) did not identify any relevant literature, but an unpublished study (CARBAR) was submitted by Shionogi that contained useful data. Review 6 indicated that cefiderocol does not appear to increase the risk of acute kidney injury (AKI), Clostridium difficile, or any other serious adverse events, compared to non-toxic comparators (i.e. comparators other than colistin or an aminoglycoside). No study reported a comparison of cefiderocol exclusively to colistin or aminoglycosides. Event rates were generally very low or zero. Discussion of clinical evidence: There were limitations to the approach selected and analyses done. Key limitations include: susceptibility could be considered, at best, a surrogate outcome, but no pre-specified criteria for judging the suitability of the surrogate or the linking evidence were applied; linking data were limited and not specific to the pathogen-mechanism combination, and expert elicitation had to be relied upon to evidence the link in the MDS; uncertainties relating to the determination and application of breakpoints; and the NMAs results were associated with high levels of heterogeneity. Economic evidence Methods No published existing economic evaluations assessed the use of cefiderocol in the HVCSs or areas of expected usage. The manufacturer did not submit a cost-effectiveness model. A de novo decision-analytic model was developed to predict the cost and health consequences of introducing cefiderocol within the HVCSs. These were summarised as INHEs. These are estimates of the quality-adjusted life-years (QALYs) associated with introducing cefiderocol if it was supplied free of charge to the NHS, taking in to account both its health benefits and the health benefits of freeing up NHS resources (e.g. via reduced time in hospital) calculated using an estimate of health opportunity cost of £20,000/QALY. This means that for every £20,000 saved, 1 QALY of health can be generated within the NHS. The estimates of INHE will be used in subsequent negotiations to determine an appropriate payment level for cefiderocol. This quantitative analysis comprises three components: an assessment of the INHEs of introducing cefiderocol within the HVCSs at the patient level; an assessment of INHEs within the HVCSs at the population level; and an assessment of how population-level INHEs within the HVCSs might appropriately be rescaled to reflect expected usage across the English NHS. The patient-level component is structured similarly to decision models developed as part of other NICE processes and characterises the cost, mortality and morbidity consequences of introducing cefiderocol over a patient’s lifetime. Separate but related models are developed for the ES and MDS. In the ES, empiric treatment with cefiderocol is compared to: empiric treatment with a non-colistin/aminoglycoside-based treatment (MBL P. aeruginosa only); empiric treatment with colistin/aminoglycoside-based treatment (considered more toxic). In the MDS, we compare outcomes in the overall microbiology-directed cohort who receive tailored therapy with cefiderocol available as a treatment option, to outcomes when this cohort receive tailored therapy with existing AMs only. In the ES, patients are suspected to have a MDR infection, so it is necessary to model outcomes for both patients in whom this suspicion is confirmed and for those in whom this suspicion turns out to be incorrect. The probability of having the suspected pathogen/resistance mechanism is informed by Second-Generation Surveillance System (SGSS) national surveillance data supplied by PHE for this evaluation. The key driver of effectiveness is in vitro susceptibility as estimated via the evidence syntheses discussed above. Higher susceptibility reduces mortality and LoS in hospital. These relationships are based on a combination of evidence from the literature and structured expert elicitation. Colistin or aminoglycoside-based therapy is expected to be associated with higher rates of AKI than other agents (including cefiderocol), which has significant consequences for patients’ short- and long-term mortality, morbidity and costs. Safety differences between colistin or aminoglycoside-based therapy and other agents are, therefore, modelled using evidence from published systematic reviews. Lifetime costs, quality of life and mortality were predicted accounting for the highly comorbid nature of the patient population and the increased risk of chronic kidney disease (CKD) resulting from AKI. The population-level component uses a forecast-based approach to aggregate the patient-level predictions to the population level accounting for the size of, and growth over time in, the eligible patient population in England within each HVCS. This component also reflects how resistance is likely to develop to cefiderocol and existing AMs over time. Predictions of population-level INHE are presented for patients initiated on treatment over the next 20 years. Current numbers of patients within the HVCSs were based on evidence from SGSS. Future growth in the number of patients in the HVCSs was based on statistical forecasting models fitted to time-series data from a national reference laboratory data set supplied by PHE for this evaluation. A series of scenarios reflects the potential emergence of resistance to cefiderocol. We did not model changes in resistance to existing AMs over time due to the sparsity of evidence available to inform these forecasts. Predicted overall population-level INHEs corresponding to the expected use of cefiderocol in the English NHS were generated by rescaling the population-level INHEs from the HVCSs to reflect additional areas of expected usage. These included patients with bloodstream and intra-abdominal infections (BSIs and IAIs) known or suspected to be caused by MBL Enterobacterales or MBL P. aeruginosa, and patients with infections caused by Stenotrophomonas across a range of sites (HAP/VAP, cUTI, BSIs and IAIs). This rescaling was based on population size estimates from SGSS and the use of expert opinion to inform the similarity in patient-level INHEs between the patients falling within the HVCSs and these additional sites and pathogens of interest. The literature on the economic evaluation of AMs has described a range of elements of value associated with these products that are not relevant to evaluations of other healthcare interventions. We also, therefore, summarise the extent to which these elements of value are captured within the quantitative estimates and, where this has not been possible, whether they are likely to substantively modify the quantitative estimates of value presented. Results Patient-level INHEs in the HVCS For HAP/VAP patients treated empirically, the base-case INHEs (0.15 QALYs) are similar in patients with suspected MBL Enterobacterales, and those with suspected P. aeruginosa. The results were very sensitive to the proportion of patients who have MBL Enterobacterales, use of the CLSI breakpoints, AKI risk, AKI-related mortality and long-term survival (range across scenarios: 0.00–0.23 QALYs). For patients treated in the MDS, the base-case INHEs associated with cefiderocol are much higher for MBL P. aeruginosa (0.15 QALYs for HAP/VAP and cUTI) than MBL Enterobacterales (0.02 QALYs for HAP/VAP and cUTI) as the latter patient group has a higher probability of being susceptible to a non-colistin/aminoglycoside-based treatment, and hence not requiring treatment with cefiderocol. There is a large degree of uncertainty in the patient-level INHE in the MBL P. aeruginosa population (range across scenarios 0.01–0.25). This reflects uncertainties in the susceptibility to non-colistin/aminoglycoside-based treatments. Results in the MBL P. aeruginosa populations are subject to additional uncertainty due to limitations in the evidence base for the comparators (fosfomycin plus meropenem and fosfomycin plus colistin), as fosfomycin does not have an established breakpoint for P. aeruginosa, making links to clinical outcomes more tenuous. Furthermore, the available evidence to inform the relative susceptibility of fosfomycin was based on very small studies (n = 7 in the EUCAST and n = 20 in the CLSI networks). We were unable to select a base case for the population-level results. Population-level results are, therefore, presented for two different approaches to estimating infection numbers (based on different methods to classify infections from clinical specimen sites); two alternative approaches to forecasting increases in infections over time (based on whether observed trends are assumed to persist indefinitely or not); and three different trajectories with respect to resistance emergence to cefiderocol (1%, 5% and 10% at 20 years). Across these scenarios, population-level INHEs range from 896 to 3559 QALYs. The results are particularly sensitive to the assumption about which clinical specimen sites are indicative of HAP/VAP. A substantial part of the value of cefiderocol (20 to 38% depending on scenario) is generated among patients with Stenotrophomonas who were outside of the HVCSs considered by EEPRU. Departures from the base-case assumptions in the patient-level model also had substantial effects on the mean population-level INHEs. The population size estimates used to generate the estimates of population-level INHEs are subject to additional uncertainties relating to the completeness of the national data, whether all tested patients would fall within the HVCS population for empiric treatment, the potential double counting of samples from the same infectious episode and inherent uncertainties in forecasting population size over time. In addition, estimates of population-level INHEs were generated using a number of strong assumptions about how evidence can be generalised between settings. Namely, that patient-level INHE of cefiderocol in patients with BSI can be approximated based on outcomes in HAP/VAP patients, and that the patient-level INHE of cefiderocol in patients with IAI can be proxied by that in patients with cUTI. These assumptions were based on discussions with clinical experts. Based on the available evidence, we concluded that diversity value, transmission value and spectrum value were unlikely to be significant drivers of population-level INHEs for cefiderocol. Insurance value was captured for the HVCS, though the benefits of cefiderocol use in novel future outbreaks were not captured and remain highly uncertain. EEPRU considers that it is possible that cefiderocol use will facilitate additional or at least more prompt receipt of required treatments/procedures for certain groups but that the magnitude of these enablement benefits remains highly uncertain. Conclusion The quantitative assessment of value in this report indicates that cefiderocol is associated with a base-case population-level INHE across its areas of expected usage of 896 to 3559 QALYs over 20 years. T

β-lactamases inactivate β-lactam antibiotics leading to drug resistance. Consequently, inhibitors of β-lactamases can combat this resistance, and the β-lactamase inhibitory protein (BLIP) is a naturally occurring inhibitor. The widespread CTX-M-14 and CTX-M-15 β-lactamases have an 83% sequence identity. In this study, we show that BLIP weakly inhibits CTX-M-14 but potently inhibits CTX-M-15. The structure of the BLIP/CTX-M-15 complex reveals that binding is associated with a conformational change of an active site loop of β-lactamase. Surprisingly, the loop structure in the complex is similar to that in a drug-resistant variant (N106S) of CTX-M-14. We hypothesized that the pre-established favorable loop conformation of the N106S mutant would facilitate binding. The N106S substitution results in a ~100- and 10-fold increase in BLIP inhibition potency for CTX-M-14 and CTX-M-15, respectively. Thus, this indicates that an active site loop in β-lactamase toggles between conformations that control antibiotic hydrolysis and inhibitor susceptibility. These findings highlight the role of accessible active site conformations in controlling enzyme activity and inhibitor susceptibility as well as the influence of mutations in selectively stabilizing discrete conformations.

ObjectivesThe gastrointestinal tract constitutes a complex and diverse ecosystem. Escherichia coli is one of the most frequently studied and characterised species in the gut ecosystem; nevertheless, there has been little research to determine their diversity and population dynamics in the intestines of children over time. We analysed the turnover or dominant E. coli isolates in children faecal matter during 1 year.MethodsIn this prospective study, a fresh faecal sample was obtained from children longitudinally over one year (30 faecal samples at sampling period 1 and 22 faecal samples at sampling periods 2 and 3). From each stool sample, five E. coli colonies were randomly selected (n = 405 E. coli isolates total) in order to characterize the genotype and phenotypic antimicrobial resistance patterns.ResultsWe were unable to find same E. coli dominant clone in faecal matter from 30 children in different sampling periods. Whole-genome sequencing of three isolates belonging to ST131 found in one child during the sampling period I and II indicated that isolates were three different ST 131 clones that carried extended-spectrum β-lactamase (ESBL) genes.ConclusionWe found that all numerically dominant E. coli lineages in children's intestines were transient colonisers, and antimicrobial resistance phenotypes of these strains varied significantly over time without any apparent selective force.

Introduction: Plasmid-mediated class C ß-lactamase (pAmpC) is a member of broad-spectrum ß-lactamase that spreads worldwide. However, its prevalence was under-evaluated. Objective: To characterize the prevalence and distribution of pAmpC types in 294 cefoxitin (FOX) and third-generation cephalosporin (3GC) resistant Enterobacteriaceae collected in several regions of Thailand and Vietnam in 2018 and 2020. Methods: Multiplex Polymerase Chain Reaction (PCR) for pAmpC identification was utilized to investigate prevalence and diversification of pAmpC among 294 cefoxitin and third-generation cephalosporin resistant Enterobacteriaceae isolated from Thailand (n= 197) and Vietnam (n= 97). Results: The prevalence of pAmpC was 37.1 % found in second and third-generation cephalosporin resistant Enterobacteriaceae. CMY-2 like was prominent in Thailand and Vietnam; however, prevalence of CMY-2 was varied in each hospital. DHA contributed 25.7 %, ACT/MIR rate was dominant in Chiang Rai hospital, reached 100 % in Thanh Hoa Pediatrics hospital. Worrisome, 3.7 % - isolates carried two types of pAmpC. The incidence of pAmpC in Vietnam was significantly higher than those in Thailand. Conclusions: These findings provide evidence-based of highly spreading and diversified distribution of transferable AmpC among Enterobacteriaceae in two Asia-Pacific countries.

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli cause severe health hazards. Migratory birds are reservoirs and transmitters of many pathogens including ESBL-producing E. coli. To examine migratory birds as potential carriers of ESBL-producing E. coli and E. coli-carrying antibiotic resistance genes, 55 PCR-positive E. coli isolates were screened using the disk diffusion method, double-disk synergy test, and further polymerase chain reaction (PCR) tests. Genes encoding resistance to tetracycline [tetA, 100% (35/35); tetB, 31.43% (11/35)], fluoroquinolone [qnrA, 35.71% (10/28); qnrB, 25% (7/28)], and streptomycin [aadA1, 90.24% (37/41)] were detected in the isolated E. coli. Of the 55 E. coli isolates, 21 (38.18%) were ESBL producers, and all of them were multidrug resistant. All the ESBL-producing E. coli isolates harbored at least two or more beta-lactamase genes, of which blaTEM, blaCMY, blaCTX-M, and blaSHV were detected in 95.24%, 90.48%, 85.71%, and 42.86% of isolates, respectively. All the beta-lactamase genes were present in four of the ESBL-producing E. coli isolates. Furthermore, 95.24% of ESBL-producing E. coli isolates were positive for one or more antibiotic resistance genes. To the best of our knowledge, this is the first study to detect E. coli-carrying antibiotic resistance genes including beta-lactamase blaCMY and blaSHV originating from migratory birds in Bangladesh. These results suggest that migratory birds are potential carriers of ESBL-producing E. coli along with other clinically important antibiotic resistance genes which may have detrimental impacts on human health.

Despite the advances in β-lactamase inhibitor development, limited options exist for the class D carbapenemase known as OXA-48. OXA-48 is one of the most prevalent carbapenemases in carbapenem-resistant Enterobacteriaceae infections and is not susceptible to most available β-lactamase inhibitors. Here, we screened various low-molecular-weight compounds (fragments) against OXA-48 to identify functional scaffolds for inhibitor development. Several biphenyl-, naphthalene-, fluorene-, anthraquinone-, and azobenzene-based compounds were found to inhibit OXA-48 with low micromolar potency despite their small size. Co-crystal structures of OXA-48 with several of these compounds revealed key interactions with the carboxylate-binding pocket, Arg214, and various hydrophobic residues of β-lactamase that can be exploited in future inhibitor development. A number of the low-micromolar-potency inhibitors, across different scaffolds, synergize with ampicillin to kill Escherichia coli expressing OXA-48, albeit at high concentrations of the respective inhibitors. Additionally, several compounds demonstrated micromolar potency toward the OXA-24 and OXA-58 class D carbapenemases that are prevalent in Acinetobacter baumannii. This work provides foundational information on a variety of chemical scaffolds that can guide the design of effective OXA-48 inhibitors that maintain efficacy as well as potency toward other major class D carbapenemases.

BackgroundThe rapid spread of extended-spectrum beta-lactamase-producing E. coli (ESBL-EC) is an urgent global health threat. We examined child caretaker knowledge, attitudes, and practices (KAP) towards proper antimicrobial agent use and whether certain KAP were associated with ESBL-EC colonization of their children.MethodsChild caretakers living in semi-rural neighborhoods in peri-urban Quito, Ecuador were visited and surveyed about their KAP towards antibiotics. Fecal samples from one child (less than 5 years of age) per household were collected at two time points between July 2018 and May 2019 and screened for ESBL-EC. A repeated measures analysis with logistic regression was used to assess the relationship between KAP levels and child colonization with ESBL-EC.ResultsWe analyzed 740 stool samples from 444 children living in households representing a range of environmental conditions. Of 374 children who provided fecal samples at the first household visit, 44 children were colonized with ESBL-EC (11.8%) and 161 were colonized with multidrug-resistant E. coli (43%). The prevalences of ESBL-EC and multidrug-resistant E. coli were similar at the second visit (11.2% and 41.3%, respectively; N = 366). Only 8% of caretakers knew that antibiotics killed bacteria but not viruses, and over a third reported that they "always" give their children antibiotics when the child's throat hurts (35%). Few associations were observed between KAP variables and ESBL-EC carriage among children. The odds of ESBL-EC carriage were 2.17 times greater (95% CI: 1.18-3.99) among children whose caregivers incorrectly stated that antibiotics do not kill bacteria compared to children whose caregivers correctly stated that antibiotics kill bacteria. Children from households where the caretaker answered the question "When your child's throat hurts, do you give them antibiotics?" with "sometimes" had lower odds of ESBL-EC carriage than those with a caretaker response of "never" (OR 0.48, 95% CI 0.27-0.87).ConclusionCaregivers in our study population generally demonstrated low knowledge regarding appropriate use of antibiotics. Our findings suggest that misinformation about the types of infections (i.e. bacterial or viral) antibiotics should be used for may be associated with elevated odds of carriage of ESBL-EC. Understanding that using antibiotics is appropriate to treat infections some of the time may reduce the odds of ESBL-EC carriage. Overall, however, KAP measures of appropriate use of antibiotics were not strongly associated with ESBL-EC carriage. Other individual- and community-level environmental factors may overshadow the effect of KAP on ESBL-EC colonization. Intervention studies are needed to assess the true effect of improving KAP on laboratory-confirmed carriage of antimicrobial resistant bacteria, and should consider community-level studies for more effective management.

BackgroundThe prevalence of infections caused by extended-spectrum beta-lactamase producing Escherichia coli (ESBL-E. coli) is increasing worldwide, but the setting in which this increase is occurring is not well defined. We compared trends and risk factors for ESBL-E. coli bacteriuria in community vs healthcare settings.MethodsWe collected electronic health record data on all patients with E. coli isolated from urine cultures in a safety-net public healthcare system from January 2014 to March 2020. All analyses were stratified by healthcare-onset/associated (bacteriuria diagnosed > 48 h after hospital admission or in an individual hospitalized in the past 90 days or in a skilled nursing facility resident, N = 1277) or community-onset bacteriuria (bacteriuria diagnosed  65 (RR 1.88, CI 1.17, 3.05), male gender (RR 2.12, CI 1.65, 2.73), and Latinx race/ethnicity (RR 1.52, CI 0.99, 2.33) were associated with community-onset ESBL-E. coli. Only male gender (RR 1.53, CI 1.03, 2.26) was associated with healthcare-onset/associated ESBL-E. coli.ConclusionsESBL-E. coli bacteriuria frequency increased at a faster rate in healthcare-associated settings than in the community between 2014 and 2020. Male gender was associated with ESBL-E. coli bacteriuria in both settings, but additional risks-age > 65 and Latinx race/ethnicity-were observed only in the community.

Here, we illustrate what happens inside the catalytic cleft of an enzyme when substrate or ligand binds on single-millisecond timescales. The initial phase of the enzymatic cycle is observed with near-atomic resolution using the most advanced X-ray source currently available: the European XFEL (EuXFEL). The high repetition rate of the EuXFEL combined with our mix-and-inject technology enables the initial phase of ceftriaxone binding to the Mycobacterium tuberculosis β-lactamase to be followed using time-resolved crystallography in real time. It is shown how a diffusion coefficient in enzyme crystals can be derived directly from the X-ray data, enabling the determination of ligand and enzyme-ligand concentrations at any position in the crystal volume as a function of time. In addition, the structure of the irreversible inhibitor sulbactam bound to the enzyme at a 66 ms time delay after mixing is described. This demonstrates that the EuXFEL can be used as an important tool for biomedically relevant research.

Backbone chemical shift assignments for the Toho-1 β-lactamase (263 amino acids, 28.9 kDa) are reported based on triple resonance solution-state NMR experiments performed on a uniformly 2H,13C,15N-labeled sample. These assignments allow for subsequent site-specific characterization at the chemical, structural, and dynamical levels. At the chemical level, titration with the non-β-lactam β-lactamase inhibitor avibactam is found to give chemical shift perturbations indicative of tight covalent binding that allow for mapping of the inhibitor binding site. At the structural level, protein secondary structure is predicted based on the backbone chemical shifts and protein residue sequence using TALOS-N and found to agree well with structural characterization from X-ray crystallography. At the dynamical level, model-free analysis of 15N relaxation data at a single field of 16.4 T reveals well-ordered structures for the ligand-free and avibactam-bound enzymes with generalized order parameters of ~ 0.85. Complementary relaxation dispersion experiments indicate that there is an escalation in motions on the millisecond timescale in the vicinity of the active site upon substrate binding. The combination of high rigidity on short timescales and active site flexibility on longer timescales is consistent with hypotheses for achieving both high catalytic efficiency and broad substrate specificity: the induced active site dynamics allows variously sized substrates to be accommodated and increases the probability that the optimal conformation for catalysis will be sampled.

Weiqiang Xiao,1,&ast; Xiaokun Wang,1,&ast; Yuanye Qu,1 Mingyue Sun,1 Yanmin Chang,1 Wenjiao Li,1 Yong Shen,1,2 Xiufang Shi,3 Min Jing,1 Qingxia Xu1,4 1Department of Clinical Laboratory, Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou, People’s Republic of China; 2Institute of Biophysics, Chinese Academy of Sciences, Foshan, People’s Republic of China; 3School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, People’s Republic of China; 4Zhengzhou Key Laboratory for Diagnosis of Digestive System Tumor Markers, Zhengzhou, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Qingxia Xu; Xiufang Shi, Email zlyyxuqingxia0575@zzu.edu.cn; xfshi@zzu.edu.cnBackground: Emergence of blaKPC and blaNDM co-harboring Klebsiella pneumoniae has escalated the threat of Carbapenem-resistant Klebsiella pneumoniae (CRKP) to healthcare. It remains unknown the prevalence and molecular characteristics of CRKP co-producing KPC and NDMs carbapenemases in Henan.Methods and Results: Twenty-seven CRKP strains isolated from different times were selected randomly in affiliated cancer hospital of Zhengzhou University from January 2019 to January 2021, among which one KPC-2 and NDM-5 positive CRKP named K9 was isolated from an abdominal pus sample of a 63-year-old male patient with leukemia. Sequencing of K9 determined that K9 belonged to ST11-KL47, which is resistant to antibiotics such as meropenem, ceftazidime-avibactam and tetracycline. K9 carried two different plasmids that contained blaNDM− 5 and blaKPC− 2. Both plasmids were shown to be novel hybrid plasmids and IS 26 played an important role in generation of two plasmids. Gene blaKPC-2 was flanked by the NTEKPC-Ib-like genetic structure (IS 26-ΔTn 3-ISKpn8-blaKPC-2-ISKpn6-IS 26) and was located on a conjugative IncFII/R/N type hybrid plasmid.Conclusion: The resistance gene blaNDM− 5 located on a region organized as IS 26-blaNDM– 5-ble-trpF-dsbD-ISCR1-sul1-aadA2-dfrA12-IntI1-IS 26 was carried by a phage-plasmid. We described a clinical CRKP co-producing KPC-2 and NDM-5 and emphasized an urgent need to control their further spread.Keywords: carbapenem-resistant Klebsiella pneumoniae, KPC-2, NDM-5, beta-lactamases, hybrid plasmid, IS 26

ABSTRACT The bla PAC-1 has been reported in Central Asia and Europe countries like Afghanistan and France in Aeromonas caviae and Pseudomonas aeruginosa strains from animals and patients, respectively. However, there is no record of bla PAC-1-carrying strain from the natural environment, and bla PAC-1-carrying Aeromonas has not been reported in the Asia Pacific. Here, we report the first known enviromental bla PAC-1-carrying Aeromonas enteropelogenes in the world from reservoir water in Singapore. We have performed a comprehensive genetic environment alignment and comparison of bla PAC-1 between our strain and other strains from different countries and sources and found the bla PAC-1 located on a highly conserved gene cluster. We suggest that environmental Aeromonas strains may act as a hidden reservoir involved in the circulating of bla PAC-1. The finding of conserved bla PAC-1 cluster also suggested the existence of multiple transmission pathways of bla PAC-1 in the Asia-Pacific region, involving multiple sources and different species.

Infections caused by extended-spectrum β-lactamase-producing Enterobacterales have increased rapidly and are mainly attributed to the production of CTX-M enzymes. This study evaluated the NG-Test® CTX-M MULTI lateral flow assay (CTX-M LFA) and the Rapid ESBL NP® test (ESBL NP test) for rapid detection of CTX-M-producing Enterobacterales directly in midstream urine (MSU) samples. Testing was performed on 277 clinical MSU samples in a hospital microbiology laboratory from November 2022 to January 2023; 60 of these samples (30 positive for ESBL producers and 30 positive for non-ESBL producers) were tested retrospectively after the identification and susceptibility results were obtained, and 217 samples were tested prospectively immediately after a Gram stain showing the presence of Gram-negative bacilli. The results were compared against phenotypic detection of ESBL and molecular testing as the reference methods. Overall, 67 of the 277 samples were culture-positive for ESBL-producing Enterobacterales. PCR for the blaCTX-M gene was positive for all ESBL-producing Enterobacterales isolates. All CTX-M LFA results were interpretable, while three of the ESBL NP test results were noninterpretable. The sensitivity of the CTX-M LFA (100%, 95% CI 94.6–100%) was higher than that of the ESBL NP test (86.6%, 95% CI 76.0–93.7%). Both tests had high specificities (CTX-M LFA, 99.1%, 95% CI 96.6–99.9% and ESBL NP test, 100%, 95% CI 98.2–100%). In conclusion, both the CTX-M LFA and the ESBL NP test can deliver rapid results that could improve antimicrobial stewardship for urinary tract infections. [ABSTRACT FROM AUTHOR]

Introduction: Fluoroquinolones (FQs) are not commonly prescribed in children, yet the increasing incidence of multidrug-resistant (MDR) Enterobacterales (Ent) infections in this population often reveals FQ resistance. We sought to define the role of FQ resistance in the epidemiology of MDR Ent in children, with an overall goal to devise treatment and prevention strategies. Methods: A case--control study of children (0-18 years) at three Chicago hospitals was performed. Cases had infections by FQ-susceptible, β-lactamase-producing (bla) Ent harboring a non- or low-level expression of PMFQR genes (PMFQS Ent). Controls had FQR infections due to bla Ent with expressed PMFQR genes (PMFQR Ent). We sought bla genes by PCR or DNA (BD Max Check-Points assay®) and PMFQR genes by PCR. We performed rep-PCR, MLST, and E. coli phylogenetic grouping. Whole genome sequencing was additionally performed on PMFQS Ent positive isolates. Demographics, comorbidities, and device, antibiotic, and healthcare exposures were evaluated. Predictors of infection were assessed. Results: Of 170 β-lactamase-producing Ent isolates, 85 (50%) were FQS; 23 (27%) had PMFQR genes (PMFQS cases). Eighty-five (50%) were FQR; 53 (62%) had PMFQR genes (PMFQR controls). The median age for children with PMFQS Ent and PMFQR Ent was 4.3 and 6.2 years, respectively (p = NS). Of 23 PMFQS Ent, 56% were Klebsiella spp., and of 53 PMFQR Ent, 76% were E. coli. The most common bla and PMFQR genes detected in PMFQS Ent were blaSHV ESBL (44%) and oqxAB (57%), and the corresponding genes detected in PMFQR Ent were blaCTX-M-1-group ESBL (79%) and aac(6')-Ib-cr (83%). Whole genome sequencing of PMFQS Ent revealed the additional presence of mcr-9, a transferable polymyxin resistance gene, in 47% of isolates, along with multiple plasmids and mobile genetic elements propagating drug resistance. Multivariable regression analysis showed that children with PMFQS Ent infections were more likely to have hospital onset infection (OR 5.7, 95% CI 1.6-22) and isolates containing multiple bla genes (OR 3.8, 95% CI 1.1-14.5). The presence of invasive devices mediated the effects of healthcare setting in the final model. Differences in demographics, comorbidities, or antibiotic use were not found. Conclusions: Paradoxically, PMFQS Ent infections were often hospital onset and PMFQR Ent infections were community onset. PMFQS Ent commonly coharbored multiple bla and PMFQR genes, and additional silent, yet transferrable antibiotic resistance genes such as mcr-9, affecting therapeutic options and suggesting the need to address infection prevention strategies to control spread. Control of PMFQS Ent infections will require validating community and healthcare-based sources and risk factors associated with acquisition. [ABSTRACT FROM AUTHOR]

Background: Intensive care units (ICU) are the epicenter of antimicrobial resistance (AMR), and patients' infections are mainly caused by Gram-negative bacteria (GNB). Objective: To describe the frequency and trends in AMR of GNB deriving from the clinical samples of ICU patients at a tertiary care hospital in Mérida, Yucatán. Material and methods: Study which included the review of laboratory reports of all bacteriological samples collected from patients admitted to neonatal, pediatric and adult ICU from January 1 2019 to December 31 2021. Results: 433 GNB isolates were recovered, with Klebsiella pneumoniae being the most predominant isolate (n = 117; 27.02%). The majority of GNB were recovered from bronchial secretions (n = 163). Overall, GNB showed high resistance rates to ampicillin (89.48%), ampicillin/sulbactam (66.85%), cephalosporins (58.52-93.81%), tobramycin (58.06%), and tetracycline (61.73%). Among GNB, 73.90% and 68.53% exhibited multidrug-resistant, and highly resistant microorganisms' profiles, respectively, and 47.54% of Acinetobacter baumannii exhibited an extensively drug-resistant profile. A total of 80.33% of A. baumannii was carbapenem-resistant, and 83.76% of K. pneumoniae strains were ESBL-producing. Conclusion: Our data could be helpful to improve the empirical therapy and the infection-control program. [ABSTRACT FROM AUTHOR]

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The recommended therapy for severe infections caused by AmpC-inducible Enterobacterales (AmpC-E) typically involves cefepime or carbapenems. In an era of emerging resistance to these antimicrobials, we aim to assess the impact of third-generation cephalosporins (3GCs) vs. alternative antibiotics on clinical outcomes in bloodstream infections (BSIs) due to AmpC-E. We retrospectively included hospitalized adult patients with BSIs caused by 3GC-susceptible AmpC-E between 2012 and 2022, comparing the outcomes of 3GC and non-3GC definitive therapies. The primary outcome was overall treatment failure (OTF), encompassing 90-day all-cause mortality, 90-day reinfection, and 90-day readmission. Secondary outcomes comprised components of the OTF, in-hospital all-cause mortality, and length-of-stay. Within a total cohort of 353 patients, OTF occurred in 46.5% and 41.5% in the 3GC- and non-3GC-therapy groups, respectively (p = 0.36). The 3GC-therapy group exhibited a longer length-of-stay (38 vs. 21 days, p = 0.0003) and higher in-hospital mortality (23.3% vs. 13.4%, p = 0.019). However, the 90-day mortality, 90-day reinfection, and 90-day readmission were comparable between the therapy groups. Subgroup analyses involving high-risk AmpC-E and 3GC vs. standard-of-care yielded similar conclusions. Overall, our findings suggest that 3GC definitive therapy may not result in poorer clinical outcomes for the treatment of BSIs caused by AmpC-E. [ABSTRACT FROM AUTHOR]

Serial femtosecond crystallography has opened up many new opportunities in structural biology. In recent years, several approaches employing light-inducible systems have emerged to enable time-resolved experiments that reveal protein dynamics at high atomic and temporal resolutions. However, very few enzymes are light-dependent, whereas macromolecules requiring ligand diffusion into an active site are ubiquitous. In this work we present a drop-on-drop sample delivery system that enables the study of enzyme-catalyzed reactions in microcrystal slurries. The system delivers ligand solutions in bursts of multiple picoliter-sized drops on top of a larger crystal-containing drop inducing turbulent mixing and transports the mixture to the X-ray interaction region with temporal resolution. We demonstrate mixing using fluorescent dyes, numerical simulations and time-resolved serial femtosecond crystallography, which show rapid ligand diffusion through microdroplets. The drop-on-drop method has the potential to be widely applicable to serial crystallography studies, particularly of enzyme reactions with small molecule substrates.

New Delhi metallo-β-lactamase (NDM) grants resistance to a broad spectrum of β-lactam antibiotics, including last-resort carbapenems, and is emerging as a global antibiotic resistance threat. Limited zinc availability adversely impacts the ability of NDM-1 to provide resistance, but a number of clinical variants have emerged that are more resistant to zinc scarcity (e.g., NDM-15). To provide a novel tool to better study metal ion sequestration in host-pathogen interactions, we describe the development of a fluorescent probe that reports on the dynamic metalation state of NDM within Escherichia coli. The thiol-containing probe selectively coordinates the dizinc metal cluster of NDM and results in a 17-fold increase in fluorescence intensity. Reversible binding enables competition and time-dependent studies that reveal fluorescence changes used to detect enzyme localization, substrate and inhibitor engagement, and changes to metalation state through the imaging of live E. coli using confocal microscopy. NDM-1 is shown to be susceptible to demetalation by intracellular and extracellular metal chelators in a live-cell model of zinc dyshomeostasis, whereas the NDM-15 metalation state is shown to be more resistant to zinc flux. The development of this reversible turn-on fluorescent probe for the metalation state of NDM provides a new tool for monitoring the impact of metal ion sequestration by host defense mechanisms and for detecting inhibitor-target engagement during the development of therapeutics to counter this resistance determinant.

In an effort to probe the biophysical mechanisms of inhibition for ten previously-reported inhibitors of metallo-β-lactamases (MBL) with MBL IMP-1, equilibrium dialysis, metal analyses coupled with atomic absorption spectroscopy (AAS), native state mass spectrometry (native MS), and ultraviolet-visible spectrophotometry (UV-VIS) were used. 6-(1H-tetrazol-5-yl) picolinic acid (1T5PA), ANT431, D/l-captopril, thiorphan, and tiopronin were shown to form IMP-1/Zn(II)/inhibitor ternary complexes, while dipicolinic acid (DPA) and 4-(3-aminophenyl)pyridine-2,6-dicarboxylic acid (3AP-DPA) stripped some metal from the active site of IMP but also formed ternary complexes. DPA and 3AP-DPA stripped less metal from IMP-1 than from VIM-2 but stripped more metal from IMP-1 than from NDM-1. In contrast to a previous report, pterostilbene does not appear to bind to IMP-1 under our conditions. These results, along with previous studies, demonstrate similar mechanisms of inhibition toward different MBLs for different MBL inhibitors.

Small molecule colloidal aggregates adsorb and partially denature proteins, inhibiting them artifactually. Oddly, this inhibition is typically time-dependent. Two mechanisms might explain this: low concentrations of the colloid and enzyme might mean low encounter rates, or colloid-based protein denaturation might impose a kinetic barrier. These two mechanisms should have different concentration dependencies. Perplexingly, when enzyme concentration was increased, incubation times actually lengthened, inconsistent with both models and with classical chemical kinetics of solution species. We therefore considered molecular crowding, where colloids with lower protein surface density demand a shorter incubation time than more crowded colloids. To test this, we grew and shrank colloid surface area. As the surface area shrank, the incubation time lengthened, while as it increased, the converse was true. These observations support a crowding effect on protein binding to colloidal aggregates. Implications for drug delivery and for detecting aggregation-based inhibition will be discussed.

Objective. To describe antimicrobial resistance profiles of Escherichia coli and Salmonella spp. isolated from chicken carcasses and the antimicrobials commonly used in animals in Ecuador and provide information on antimicrobial resistance patterns for implementing evidence-based corrective measures. Methods. Meat samples were collected from chicken carcasses in 199 slaughterhouses across Ecuador as part of a national pilot study for monitoring antimicrobial resistance in agricultural sources in 2019. Samples were tested for E. coli and Salmonella spp. Sensitivity to 10 critically important and three highly important antimicrobials (from a human health perspective) was assessed. The country report submitted to the World Organization for Animal Health was accessed to extract the quantity of antimicrobials produced or imported for use in animals. Results. Of 383 samples, E. coli was isolated from 148 (39%) and Salmonella spp. from 20 (5%) samples. Ninety percent of the isolates were resistant to at least one critically important antimicrobial. Resistance was highest to erythromycin (E. coli 76%; Salmonella spp. 85%) and tetracycline (E. coli 71%; Salmonella spp. 90%). Critically or highly important antimicrobials (colistin, tetracycline, trimethoprim/sulfamethoxazole) formed the bulk (87%) of antimicrobials used in animals as per the World Organization for Animal Health report. Conclusions. High prevalence of antimicrobial resistance in poultry in Ecuador calls for the development of guidelines and regulations on the use of antimicrobials and for engagement with livestock producers. The existing surveillance system needs to be strengthened to improve the monitoring of antimicrobial use and evolving resistance patterns.

Rongrong Li,1,2 Huaming Xu,3 Hao Tang,4 Jilu Shen,1,5 Yuanhong Xu1 1Department of Clinical Laboratory, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, People’s Republic of China; 2Department of Pathogen Biology and Provincial Laboratories of Pathogen Biology and Zoonoses, Anhui Medical University, Hefei, People’s Republic of China; 3The First Affiliated Hospital of Anhui University of Traditional Chinese Medicine, Hefei, People’s Republic of China; 4Department of Clinical Laboratory, The Second Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China; 5Anhui Public Health Clinical Center, Hefei, People’s Republic of ChinaCorrespondence: Yuanhong Xu, Department of Clinical Laboratory, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, People’s Republic of China, Tel +86 13505694447, Email xyhong1964@163.comBackground: Bloodstream infection (BSI) is a common type of infection frequently diagnosed in clinics. The emergence and spread of ESBLs-producing Escherichia coli (E. coli) has emerged as one of the biggest challenges in global community health.Methods: The production of ESBLs was determined by the composite disk diffusion method. The expression of the various resistance and virulence genes were detected by PCR and sequencing. Multi-locus sequence typing (MLST) and phylogenetic groups were used for the classification. The transfer of resistant plasmids was determined by conjugation assay. The statistical differences were analyzed using Statistical Product and Service Solutions (SPSS) version 23.0.Results: A total of 60 strains of ESBLs-producing E. coli were collected. The resistance genes that were identified included blaCTX-M, blaTEM, blaSHV, blaOXA-1 and mcr-1. The most common one was the blaCTX-M including blaCTX-M-27 (n = 16), blaCTX-M-14 (n = 15), blaCTX-M-15 (n = 11), blaCTX-M-55 (n = 14) and blaCTX-M-65 (n = 5). A total of 31 STs were detected, and the most abundant among which was ST131 (n = 16, 26.7%). Most of the E. coli (n = 46, 76.7%) belonged to the groups B2 and D. And some virulence genes were related to the classification of the E. coli. Among them, the detection rates of hek/hra, kpsMII and papGII-III in groups B2 and D were higher than those in groups A and B1. The detection rates of cnf1, iucC and papGII-III in ST131 were higher than those in non-ST131. And the distributions of hek/hra, iroN, iucC, kpsMII and papGII-III were related to the blaCTX-M subtypes. Finally, most bacterial (n = 32, 53.3%) resistance genes could be transferred between the bacteria by plasmids, especially IncFIB.Conclusion: ESBLs-producing E. coli in BSI exhibited had high resistance rates and carried a variety of virulence factors (VFs). This is necessary to strengthen the monitoring of ESBLs-producing isolates in the medical environment.Keywords: Escherichia coli, sepsis, beta-lactamases, blaCTX-M

Despite the presence of more than 100 different antibacterials in the therapeutic arsenal, beta-lactam antibiotics, in general, and the third-generation cephalosporins, in particular, remain the main option for the treatment of the most of infections in inpatients. At the same time, the widespread and oftentimes inappropriate use of the third-generation cephalosporins in Russian hospitals lead to the emergence and spread of antimicroabial resistance. The review covers the problems of antibiotic resistance to cephalosporins due to the production of beta-lactamases, the role of beta-lactamase inhibitors in overcoming this type of resistance, options for combinations of cephalosporins with beta-lactamase inhibitors, in vitro activity of cefotaxime/sulbactam and cefepime/sulbactam, the results of clinical studies, and the role of the above combinations in the treatment of infections in the hospital.

BackgroundThere is a significant gap in our understanding of the sources of multidrug-resistant bacteria and resistance genes in community settings where human-animal interfaces exist.ObjectivesThis study characterized the relationship of third-generation cephalosporin-resistant Escherichia coli (3GCR-EC) isolated from animal feces in the environment and child feces based on phenotypic antimicrobial resistance (AMR) and whole genome sequencing (WGS).MethodsWe examined 3GCR-EC isolated from environmental fecal samples of domestic animals and child fecal samples in Ecuador. We analyzed phenotypic and genotypic AMR, as well as clonal relationships (CRs) based on pairwise single-nucleotide polymorphisms (SNPs) analysis of 3GCR-EC core genomes. CRs were defined as isolates with fewer than 100 different SNPs.ResultsA total of 264 3GCR-EC isolates from children (n=21), dogs (n=20), and chickens (n=18) living in the same region of Quito, Ecuador, were identified. We detected 16 CRs total, which were found between 7 children and 5 domestic animals (5 CRs) and between 19 domestic animals (11 CRs). We observed that several clonally related 3GCR-EC isolates had acquired different plasmids and AMR genes. Most CRs were observed in different homes (n=14) at relatively large distances. Isolates from children and domestic animals shared the same blaCTX-M allelic variants, and the most prevalent were blaCTX-M-55 and blaCTX-M-65, which were found in isolates from children, dogs, and chickens.DiscussionThis study provides evidence of highly dynamic horizontal transfer of AMR genes and mobile genetic elements (MGEs) in the E. coli community and shows that some 3GCR-EC and (extended-spectrum β-lactamase) ESBL genes may have moved relatively large distances among domestic animals and children in semirural communities near Quito, Ecuador. Child-animal contact and the presence of domestic animal feces in the environment potentially serve as important sources of drug-resistant bacteria and ESBL genes. https://doi.org/10.1289/EHP7729.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) frequently causes hospital-acquired infections and is associated with high morbidity and mortality. CRKP can have multiple resistance mechanisms and only a few can be routinely detected by commercial molecular or phenotypic assays making surveillance for CRKP particularly challenging. In this report, we identified and characterized an unusual non-carbapenemase-producing CRKP carrying a rare plasmid-borne inducible AmpC gene, blaDHA-1 . The isolate was recovered from blood culture of a 67-year-old female presenting with sepsis post bladder surgery and ureteral stent removal. The primary isolate displayed an indeterminate susceptibility pattern for ceftriaxone by broth microdilution, but was susceptible by disk diffusion with one colony growing within the zone of inhibition. The ceftriaxone resistant colony was sub-cultured and had a minimum inhibitory concentration (MIC) of 2 ug/ml for imipenem (intermediate) and a zone size of 18 mm for ertapenem (resistant), but remained susceptible to cefepime and meropenem. Further phenotypic characterization of this sub-cultured isolate showed carbapenemase activity. Whole genome sequencing (WGS) revealed the presence of two subpopulations of a K. pneumoniae (MLST sequence type 11) from the primary blood culture isolate: one pan-susceptible to beta-lactams tested and the other resistant to the 3rd generation cephalosporins and ertapenem. WGS analysis identified the resistant K. pneumoniae harboring IncFIB(K) and IncR plasmids and the presence of plasmid-borne beta-lactam resistance genes bla OXA-1 and bla DHA-1, an inducible AmpC gene. Additional resistance genes against quinolones (aac(6')-Ib-cr, oqxA, oqB), aminoglycoside (aph(3')-Ia), sulfonamide (sul1), and tetracycline (tet(A)) were also identified. DHA-1 positive K. pneumoniae have been previously identified outside the US, particularly in Asia and Europe, but limited cases have been reported in the United States and may be underrecognized. Our study highlights the importance of using both extended phenotypic testing and WGS to identify emerging resistance mechanisms in clinical Enterobacterales isolates with unusual antimicrobial resistance patterns.