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• CESS-1 is a class A β-lactamase hydrolysing penicillins and cephalosporins • CESS-1 displays the highest hydrolytic activity toward cefaclor • CESS-1 distinguishes cefaclor, cephalexin, and ampicillin with similar structures • Crystal structures of CESS-1 acylated by the three substrates were determined • The structural basis for the substrate discrimination was revealed at the atomic level Stenotrophomonas spp. intrinsically resistant to many β-lactam antibiotics are found throughout the environment. CESS-1 identified in Stenotrophomonas sp. KCTC 12332 is an uncharacterized class A β-lactamase. The goal of this study was to reveal biochemical and structural characteristics of CESS-1. The hydrolytic activities of CESS-1 towards penicillins (penicillin G and ampicillin), cephalosporins (cephalexin, cefaclor, and cefotaxime), and carbapenems (imipenem and meropenem) was spectrophotometrically monitored. Structural information on E166Q mutants of CESS-1 acylated by cefaclor, cephalexin, or ampicillin were determined by X-ray crystallography. CESS-1 displayed hydrolytic activities toward penicillins and cephalosporins, with negligible activity toward carbapenems. Although cefaclor, cephalexin, and ampicillin have similar structures with identical R1 side chains, the catalytic parameters of CESS-1 toward them were distinct. The k cat values for cefaclor, cephalexin, and ampicillin were 1249.6 s-1, 204.3 s-1, and 69.8 s-1, respectively, with the accompanying K M values of 287.6 μM, 236.7 μM, and 28.8 μM, respectively. CESS-1 was able to discriminate between cefaclor and cephalexin with a single structural difference at C3 position: –Cl (cefaclor) and –CH 3 (cephalexin). Structural comparisons among three E166Q mutants of CESS-1 acylated by cefaclor, cephalexin, or ampicillin, revealed that cooperative positional changes in the R1 side chain of substrates and their interaction with the β5-β6 loop affect the distance between Asn170 and the deacylating water at the acyl-enzyme intermediate state. This is directly associated with the differential hydrolytic activities of CESS-1 toward the three structurally similar β-lactam antibiotics. [Display omitted] [ABSTRACT FROM AUTHOR]

• Only a subset of European centres routinely conducted susceptibility testing for new antibiotics, characterised the AmpC overproduction resistance mechanism, and provided identification of carbapenemase enzymes in ESCPM species. • ESCPM species displayed third-, combined third- and fourth-generation cephalosporins, and carbapenems resistance phenotypes in 15.7%, 4.6%, and 9.5% of the isolates, respectively. • ESBL expression, AmpC overproduction, and carbapenemase production were detected in 6.4%, 15.8%, and 3.1% of the isolates, respectively. • E. cloacae complex and S. marcescens emerged as the most frequently detected species , with the former displaying ESBL production, AmpC overproduction and carbapenemase production in 11.4%, 17.1%, and 3.5% of the isolates, respectively. • Klebsiella aerogenes showed the highest rate of both 3GC resistant phenotype (29.8%) and AmpC overproduction (32.1%), while providencia species those of both carbapenems resistance phenotype (42.7%) and carbapenemase production (29.4%). • Among carbapenemases, VIM and OXA-48 enzymes were the most frequently identified in ESCPM species. • Although its use as monotherapy is discouraged, colistin emerged as the most active drug against ESCPM species (except those intrinsically resistant) displaying both carbapenem resistance phenotype and carbapenemase production. The ESCPM group (Enterobacter species including Klebsiella aerogenes - formerly Enterobacter aerogenes, Serratia species, Citrobacter freundii complex, Providencia species and Morganella morganii) has not yet been incorporated into systematic surveillance programs. We conducted a multicentre retrospective observational study analysing all ESCPM strains isolated from blood cultures in 27 European hospitals over a 3-year period (2020–2022). Diagnostic approach, epidemiology, and antimicrobial susceptibility were investigated. Our study comprised 6,774 ESCPM isolates. MALDI-TOF coupled to mass spectrometry was the predominant technique for bacterial identification. Susceptibility to new β-lactam/β-lactamase inhibitor combinations and confirmation of AmpC overproduction were routinely tested in 33.3% and 29.6% of the centres, respectively. The most prevalent species were E. cloacae complex (44.8%) and S. marcescens (22.7%). Overall, third-generation cephalosporins (3GC), combined third- and fourth-generation cephalosporins (3GC + 4GC) and carbapenems resistance phenotypes were observed in 15.7%, 4.6%, and 9.5% of the isolates, respectively. AmpC overproduction was the most prevalent resistance mechanism detected (15.8%). Among carbapenemase-producers, carbapenemase type was provided in 44.4% of the isolates, VIM- (22.9%) and OXA-48-enzyme (16%) being the most frequently detected. E. cloacae complex, K. aerogenes and Providencia species exhibited the most notable cumulative antimicrobial resistance profiles, with the former displaying 3GC, combined 3GC + 4GC and carbapenems resistance phenotypes in 15.2%, 7.4%, and 12.8% of the isolates, respectively. K. aerogenes showed the highest rate of both 3GC resistant phenotype (29.8%) and AmpC overproduction (32.1%), while Providencia species those of both carbapenems resistance phenotype (42.7%) and carbapenemase production (29.4%). ESCPM isolates exhibiting both 3GC and combined 3GC + 4GC resistance phenotypes displayed high susceptibility to ceftazidime/avibactam (98.2% and 95.7%, respectively) and colistin (90.3% and 90.7%, respectively). Colistin emerged as the most active drug against ESCPM species (except those intrinsically resistant) displaying both carbapenems resistance phenotype (85.8%) and carbapenemase production (97.8%). This study presented a current analysis of ESCPM species epidemiology in Europe, providing insights to inform current antibiotic treatments and guide strategies for antimicrobial stewardship and diagnostics. [ABSTRACT FROM AUTHOR]

• Cefiderocol activity is impaired by several extended spectrum oxacillinases in P. aeruginosa. • ES-OXAs may confer cross-resistance between ceftolozane/tazobactam and cefiderocol. • Several point mutations in oxacillinases are associated with cefiderocol resistance. • ES-OXAs may compromise the efficacy of cefiderocol in clinical strains of P. aeruginosa. Cefiderocol has an excellent in vitro activity on clinical strains of Pseudomonas aeruginosa (P. aeruginosa). However, the resistance of some isolates has been associated with the production of some β-lactamases. Whether some acquired extended-spectrum oxacillinases (ES-OXA) common in this species may compromise the susceptibility of P. aeruginosa to cefiderocol has not been evaluated so far. Eighteen genes encoding OXA belonging to the major subgroups identified in P. aeruginosa OXA-1 (n = 3); − 2 (n = 5); − 10 (n = 8), and − 46 (n = 2) were cloned into pUCP24 shuttle vector and transferred into reference strain PAO1. Although production of the OXA-1 subgroup enzymes did not alter cefiderocol MICs, the β-lactamases of OXA-2, OXA-46, and four variants of the OXA-10 subgroup resulted in an 8-fold to 32-fold decrease in susceptibility in the PAO1 background. Interestingly, point mutations Ala149Pro and Asp150Gly in OXA-2 subgroup, Trp154Cys and Gly157Asp in OXA-10 subgroup (all located in the Ω loop), and the duplication of a Thr206 and a Gly207 in the β5-β6 loop of OXA-10 subgroup were related to decreased susceptibility to cefiderocol. We also showed that some ES-OXA, including the most frequent ES-OXA in P. aeruginosa strains, OXA-19 (derived from OXA-10 subgroup), significantly compromised activity of cefiderocol in addition to ceftazidime, ceftolozane/tazobactam, and ceftazidime/avibactam in clinical strains. This work shows that several ES-OXA have a significant effect on cefiderocol susceptibility. Of concern are the Trp154Cys and Gly157Asp mutations that occur in some of these β-lactamases, as they are associated with a decreased activity of the most recent cephalosporins introduced to combat P. aeruginosa infections. [ABSTRACT FROM AUTHOR]

Extended-spectrum-beta-lactamase (ESBL)-producing Enterobacterales as a cause of community-acquired uncomplicated urinary tract infection (UTI) is on the rise. Currently, there are minimal oral treatment options. New combinations of existing oral third-generation cephalosporins paired with clavulanate may overcome resistance mechanisms seen in these emerging uropathogens. Ceftriaxone-resistant Escherichia coli and Klebsiella pneumoniae containing CTX-M-type ESBLs or AmpC, in addition to narrow-spectrum OXA and SHV enzymes, were selected from blood culture isolates obtained from the MERINO trial. Minimum inhibitory concentration (MIC) values of third-generation cephalosporins (cefpodoxime, ceftibuten, cefixime, cefdinir), both with and without clavulanate, were determined. One hundred and one isolates were used with ESBL, AmpC and narrow-spectrum OXA genes (e.g. OXA-1, OXA-10) present in 84, 15 and 35 isolates, respectively. Susceptibility to oral third-generation cephalosporins alone was very poor. Addition of 2 mg/L clavulanate reduced the MIC 50 values (cefpodoxime MIC 50 2 mg/L, ceftibuten MIC 50 2 mg/L, cefixime MIC 50 2 mg/L, cefdinir MIC 50 4 mg/L) and restored susceptibility (33%, 49%, 40% and 21% susceptible, respectively) in a substantial number of isolates. This finding was less pronounced in isolates co-harbouring AmpC. In-vitro activity of these new combinations may be limited in real-world Enterobacterales isolates co-harbouring multiple antimicrobial resistance genes. Pharmacokinetic/pharmacodynamic data would be useful for further evaluation of their activity. [ABSTRACT FROM AUTHOR]

• Seasonality in antimicrobial resistance (AMR) rates of community-acquired E. coli bloodstream isolates was examined. • E. coli isolates showed seasonal variation in AMR rates to four agents from frequently used classes in ambulatory settings. • The proportion of multidrug-resistant E. coli increased during peak of antimicrobial prescription in winter months. Seasonal variation in community antimicrobial consumption has been demonstrated, with the lowest utilisation rates during summer months. This retrospective cohort study examined seasonality in antimicrobial resistance (AMR) rates of community-acquired Escherichia coli bloodstream isolates. Escherichia coli bloodstream isolates (2010–2015) were identified through the central Palmetto Health microbiology laboratory database. Multivariate logistic regression was used to examine seasonal variation in AMR. Poisson regression was used to evaluate the association between proportion of multidrug-resistant (MDR) isolates and bimonthly ambulatory antimicrobial prescription rates. Among 339 unique patients with community-acquired E. coli bloodstream infection [median age 65 years; 205 (60.5%) female], AMR rates were lower during summer (June–September) than the rest of the year for amoxicillin/clavulanic acid (17% vs. 29%; aOR = 0.53, 95% CI 0.30–0.92; P = 0.02), cefazolin (6% vs. 19%; aOR = 0.26, 95% CI 0.10–0.58; P < 0.001), ceftriaxone (2% vs. 6%; aOR = 0.25, 95% CI 0.04–0.93; P = 0.04) and trimethoprim/sulfamethoxazole (9% vs. 27%; aOR = 0.27, 95% CI 0.13–0.53; P < 0.001). The proportion of MDR E. coli declined from 31–36% during peak antimicrobial prescription to 11–14% in summer months; a 6.8% decline per interval decrease in antimicrobial prescription rates of 10/100 person-years (P = 0.01). There is significant seasonal variation in AMR rates of E. coli bloodstream isolates to four agents from frequently utilised antimicrobial classes in the community. Examination of seasonal variation in dominant serotypes of community-acquired E. coli bloodstream isolates in future will be valuable. [ABSTRACT FROM AUTHOR]

• Comparison of effectiveness of fluoroquinolone (FQ)-based versus β-lactam (BL)-based regimens for complicated IAIs. • Systematic review and meta-analysis of randomised controlled trials of patients with cIAIs. • Patients with cIAIs treated with FQs had similar clinical outcomes compared with those treated with BLs. • Subgroup analyses suggested inferior outcomes for moxifloxacin monotherapy, especially for complicated appendicitis. • FQs and BLs can be used as first-line empirical treatment in patients with complicated IAIs; moxifloxacin needs more study. Complicated intra-abdominal infections (cIAIs) are common and confer significant morbidity, mortality and costs. In this era of evolving antimicrobial resistance, selection of appropriate empirical antimicrobials is paramount. This systematic review and meta-analysis of randomised controlled trials compared the effectiveness and safety of fluoroquinolone (FQ)-based versus β-lactam (BL)-based regimens for the treatment of patients with cIAIs. Primary outcomes were treatment success in the clinically evaluable (CE) population and all-cause mortality in the intention-to-treat (ITT) population. Subgroup analyses were performed based on specific antimicrobials, infection source and isolated pathogens. Seven trials (4125 patients) were included. FQ-based regimens included moxifloxacin (four studies) or ciprofloxacin/metronidazole (three studies); BL-based regimens were ceftriaxone/metronidazole (three studies), carbapenems (two studies) or piperacillin/tazobactam (two studies). There was no difference in effectiveness in the CE (2883 patients; RR = 1.00, 95% CI 0.95–1.04) or ITT populations (3055 patients; RR = 0.97, 95% CI 0.94–1.01). Mortality (3614 patients; RR = 1.04, 95% CI 0.75–1.43) and treatment-related adverse events (2801 patients; RR = 0.97, 95% CI 0.70–1.33) were also similar. On subset analysis, moxifloxacin was slightly less effective than BLs in the CE (1934 patients; RR = 0.96, 95% CI 0.93–0.99) and ITT populations (1743 patients; RR = 0.94, 95% CI 0.91–0.98). Although FQ- and BL-based regimens appear equally effective and safe for the treatment of cIAIs, limited data suggest slightly inferior results with moxifloxacin. Selection of empirical coverage should be based on local bacterial epidemiology and patterns of resistance as well as antimicrobial stewardship protocols. [ABSTRACT FROM AUTHOR]

Highlights • An ICU implemented a new standard of care with restriction of high ecological impact antibiotics. • Median length of stay, use of vasopressors and invasive ventilation decreased. • Use of carbapenems, cephalosporins, fluoroquinolones and glycopeptides decreased by ≥50%. • A switch towards lower impact antibiotics occurred (penicillins, sulfonamides and macrolides). • Resistance to piperacillin, ceftazidime, imipenem and ciprofloxacin in P. aeruginosa decreased. ABSTRACT This study aimed to assess whether post-prescription review and feedback (PPRF) of all antibiotics, with restriction of carbapenems, fluoroquinolones and third-generation cephalosporins (3GCs), along with a change in medical standard of care impacted antibiotic consumption and bacterial antimicrobial resistance in a French medical/surgical intensive care unit (ICU). A 4-year before (2007–2010) and after (2011–2014) retrospective comparative study was performed. Antibiotic consumption was evaluated in defined daily doses per 1000 patient-days. The rates of Pseudomonas aeruginosa resistance to piperacillin, ceftazidime, ciprofloxacin, imipenem and amikacin and of AmpC-hyperproducing group 3 Enterobacteriaceae were assessed. Consumption of fluoroquinolones decreased by –85%, carbapenems by –58%, 3GCs by –50% and glycopeptides by –66% (P ≤ 0.0001). Consumption of penicillins with and without β-lactamase inhibitors increased by +72% and +78%, sulfonamides by +172% and macrolides by +267% (P < 0.0001). Pseudomonas aeruginosa resistance rates for all antibiotics tested and the proportion of AmpC-hyperproducing group 3 Enterobacteriaceae decreased (P ≤ 0.01). The median length of stay, use of vasopressors and invasive mechanical ventilation decreased, and the use of renal replacement therapy increased (P < 0.05). The initial severity score (SAPS II) increased (P < 0.01) due to changes in practice, with no impact on in-hospital mortality (P = 0.07). In conclusion, changes in medical care along with PPRF and a restriction of high ecological impact antibiotics were associated with a shift towards the consumption of low ecological impact antibiotics in an ICU. Rates of resistant P. aeruginosa and of AmpC-hyperproducing group 3 Enterobacteriaceae decreased simultaneously. [ABSTRACT FROM AUTHOR]

Highlights • Cefiderocol is an investigational parenteral siderophore cephalosporin • Cefiderocol MICs were ≤4 µg/mL for 99.4% of 8954 isolates of Gram-negative bacilli • 99.6% of meropenem-non-susceptible Enterobacteriaceae had cefiderocol MICs ≤4 µg/mL • 99.7% of meropenem-non-susceptible P. aeruginosa had cefiderocol MICs ≤4 µg/mL • 96.1% of meropenem-non-susceptible Acinetobacter spp. had cefiderocol MICs ≤4 µg/mL ABSTRACT Cefiderocol (S-649266) is a parenteral siderophore cephalosporin in phase III of clinical development. In this study, we determined the in vitro susceptibility to cefiderocol and comparators of a 2015-2016 collection of 8954 clinical isolates of Gram-negative bacilli (GNB), provided by 100 clinical laboratories in North America and Europe, using the Clinical and Laboratory Standards Institute broth microdilution method. Iron-depleted cation-adjusted Mueller-Hinton broth was used to test cefiderocol. The concentration of cefiderocol inhibiting 90% of isolates (MIC 90) was 0.5 mg/L (North America; n =2470) and 1 mg/L (Europe; n =3,543) for Enterobacteriaceae, 0.5 mg/L (North America; n =619) and 0.5 mg/L (Europe; n =921) for Pseudomonas aeruginosa , 1 mg/L (North America; n =308) and 2 mg/L (Europe; n =664) for Acinetobacter spp., 0.5 mg/L (North America; n =165) and 0.25 mg/L (Europe; n =175) for Stenotrophomonas maltophilia , and 0.12 mg/L (North America; n =40) and 0.5 mg/L (Europe; n =49) for Burkholderia cepacia complex spp. Cefiderocol MICs were ≤4 mg/L for 99.9% (6005/6013) of Enterobacteriaceae, 99.9% (1539/1540) of P. aeruginosa , 96.4% (937/972) of Acinetobacter spp., 99.4% (338/340) of S. maltophilia , and 94.4% (84/89) of Burkholderia cepacia complex spp. isolates tested. Against meropenem-non-susceptible isolates, MICs to cefiderocol were ≤4 mg/L for 99.6% (245/246) of Enterobacteriaceae, 99.7% (394/395) of P. aeruginosa , 96.1% (540/562) of Acinetobacter spp., and 87.1% (27/31) of B. cepacia complex spp. We conclude that cefiderocol demonstrated potent in vitro activity (MIC ≤4 mg/L) against the majority (99.4%, 8903/8954) of clinical isolates of GNB in a recent (2015-2016), multi-continent collection, including carbapenem-non-susceptible isolates. [ABSTRACT FROM AUTHOR]

Highlights • β-Lactamase carriage and in vitro activity of cefiderocol were determined against 1272 meropenem-non-susceptible isolates. • Isolates were of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii. • No clear correlation between carriage of β-lactamases included in molecular testing algorithm and elevated cefiderocol MICs. • Cefiderocol demonstrated potent in vitro activity against carbapenemase-producing isolates. • Cefiderocol was active against colistin-resistant isolates of Enterobacteriaceae. Abstract Cefiderocol is a siderophore cephalosporin in development for treatment of infections caused by Gram-negative bacilli, including carbapenem-resistant and multidrug-resistant isolates. β-Lactamase carriage and in vitro activity of cefiderocol were determined against 1272 meropenem-non-susceptible isolates of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii collected as part of the SIDERO-WT-2014 surveillance study. Minimum inhibitory concentration (MIC) values for cefiderocol were ≤4 µg/mL against 97.7% of tested isolates, including 100% of IMP-positive (range, 1-2 µg/mL), OXA-58-positive (MIC 90 , 1 µg/mL), KPC-positive (MIC 90 , 2 µg/mL), VIM-positive (MIC 90 , 2 µg/mL), and OXA-48-like-positive (MIC 90 , 4 µg/mL) isolates; 99.3% of carbapenemase-negative isolates (MIC 90 , 1 µg/mL); 97.2% of OXA-23-positive isolates (MIC 90 , 1 µg/mL); 95.2% of OXA-24-positive isolates (MIC 90 , 1 µg/mL); 91.7% of GES-positive isolates (MIC 90 , 4 µg/mL); and 64.3% of NDM-positive isolates (MIC 90 , 8 µg/mL). A total of 29 isolates (2.3%; 15 OXA-23-producers, 6 OXA-24-producers, 5 NDM-producers, and 3 carbapenemase-negative isolates) exhibited cefiderocol MIC ≥8 µg/mL, confirming there was no clear correlation between carriage of β-lactamases included in the molecular testing algorithm and elevated cefiderocol MICs. Similarly, no correlation was observed between cefiderocol MICs and truncation or loss of porin proteins in meropenem-non-susceptible isolates of E. coli and K. pneumoniae. Cefiderocol MICs were also ≤4 µg/mL against 99.3% of 136 colistin-resistant Enterobacteriaceae collected as part of the SIDERO-WT-2014 study, including isolates carrying mcr-1 (MIC 90 , 2 µg/mL). Cefiderocol demonstrated potent in vitro activity against a collection of carbapenemase-producing and carbapenemase-negative meropenem-non-susceptible Gram-negative bacilli for which few treatment options are available, including the majority of metallo-β-lactamase producing isolates identified. [ABSTRACT FROM AUTHOR]

Highlights • New plasmid-encoded AmpC β-lactamase (CFE-2) from a clinical Citrobacter freundii isolate. • Amino acid sequence of CFE-2 showed 92% identity with plasmid-encoded enzyme CFE-1. • The bla CFE-2 gene was located on a transferable IncW plasmid. • CFE-2 is of chromosomal origin, like CFE-1 in C. freundii. • Expression of bla CEF-2 requires functional AmpR. ABSTRACT A clinical isolate of Citrobacter freundii (JA99) obtained from a bile culture of a Taiwanese patient was found to produce a plasmid-encoded β-lactamase conferring resistance to oxyimino-cephalosporins and cephamycins. Resistance arising from production of the β-lactamase could be transferred by conjugation with an IncW plasmid (pJA99) into Escherichia coli J53. The substrate and inhibition profiles of this enzyme resembled that of an AmpC β-lactamase. The resistance gene of pJA99, cloned and expressed in E. coli DH5α, was shown to contain an open reading frame showing 92% amino acid identity with the plasmid-encoded enzyme CFE-1 of E. coli KU6400. DNA sequence analysis also identified a gene upstream of ampC in pJA99 whose sequence was 95.0% identical to the ampR gene from E. coli KU6400. In addition, orf1 , the fumarate operon (frdABCD), blc, lolB and repB surrounding the ampR–ampC genes in C. freundii were identified. This DNA fragment was absent in other Citrobacter spp. Therefore, we describe a new plasmid-encoded AmpC β-lactamase, named CFE-2. This study highlights the emergence of broad-spectrum cephalosporin resistance in C. freundii owing to a new type of AmpC β-lactamase. [ABSTRACT FROM AUTHOR]

• The best therapy for wild-type AmpC β-lactamase-producing Enterobacterales is uncertain. • There was no significant difference in mortality between the study treatment groups: third-generation cephalosporin (3GC), piperacillin ± tazobactam, or cefepime/carbapenem (primary endpoint). • Both 3GC and piperacillin ± tazobactam may increase treatment failure due to AmpC-overproduction (secondary endpoint). The optimal treatment regimen for infections caused by wild-type AmpC β-lactamase-producing Enterobacterales remains controversial. This study compared the outcomes of bloodstream infections (BSI) and pneumonia according to the type of definitive antibiotic therapy: third-generation cephalosporin (3GC), piperacillin ± tazobactam, cefepime or carbapenem. All cases of BSI and pneumonia caused by wild-type AmpC β-lactamase-producing Enterobacterales over 2 years in eight university hospitals were reviewed. Patients who received definitive therapy consisting of either a 3GC (3GC group), piperacillin ± tazobactam (piperacillin group), or cefepime or a carbapenem (reference group) were included in this study. The primary endpoint was 30-day all-cause mortality. The secondary endpoint was treatment failure due to infection by emerging AmpC-overproducing strains. Propensity-score-based models were used to balance confounding factors between groups. In total, 575 patients were included in this study: 302 (52%) with pneumonia and 273 (48%) with BSI. Half (n =271, 47%) received cefepime or a carbapenem as definitive therapy, 120 (21%) received a 3GC, and 184 (32%) received piperacillin ± tazobactam. Compared with the reference group, 30-day mortality was similar in the 3GC [adjusted hazard ratio (aHR) 0.86, 95% confidence interval (CI) 0.57–1.31)] and piperacillin (aHR 1.20, 95% CI 0.86–1.66) groups. The likelihood of treatment failure was higher in the 3GC (aHR 6.81, 95% CI 3.76–12.4) and piperacillin (aHR 3.13, 95% CI 1.69–5.80) groups. The results were similar when stratifying the analysis on pneumonia or BSI. Treatment of included BSI or pneumonia caused by wild-type AmpC β-lactamase-producing Enterobacterales with 3GC or piperacillin ± tazobactam was not associated with higher mortality, but was associated with increased risk of AmpC overproduction leading to treatment failure compared with cefepime or a carbapenem. [Display omitted] [ABSTRACT FROM AUTHOR]

Cefiderocol is a siderophore cephalosporin that displays potent in vitro activity against multidrug-resistant (MDR) Gram-negative bacteria. This study aimed to describe the pharmacokinetics, pharmacodynamics and 24-h efficacy of cefiderocol using dose-ranging methods in a neutropenic murine thigh infection model. Infection was established in neutropenic mice (administered cyclophosphamide 150 mg/kg and 100 mg/kg at 4 days and 1 day prior to inoculation, respectively) with eight Pseudomonas aeruginosa isolates [minimum inhibitory concentration (MIC) range 0.063–0.5 µg/mL] that displayed variable in vivo activity against previously tested β-lactams with siderophore moieties. Renal excretion was controlled by administration of 5 mg/kg uranyl nitrate 3 days prior to inoculation. Cefiderocol was administered subcutaneously in eight escalating doses [4.2–166.7 mg/kg every 8 h (q8h)]. In pharmacokinetic studies, cefiderocol manifested similar pharmacokinetics across tested doses (4, 100 and 250 mg/kg) with a mean half-life of 0.86 h. In pharmacodynamic studies, the change in CFU after 24 h from the initial inoculum ranged from +3.4 to −3.1 log 10 with doses of 4.2–166.7 mg/kg q8h. Dose–response curves for the eight isolates assumed the characteristic sigmoidal shape, with greater CFU reductions as the dose increased. Focusing on the previously defined efficacy parameter of f T   >   MIC (time that the free drug concentration exceeds the MIC) for this compound, targets for stasis and 1 log 10 and 2 log 10 reductions ranged from 44.4–94.7, 50.2–97.5 and 62.1–100, respectively. Cefiderocol displayed sustained antibacterial effects against these MDR P. aeruginosa isolates. These data support the cefiderocol dose selected for clinical trials. [ABSTRACT FROM AUTHOR]

Extended-spectrum cephalosporin (ESC)-resistant Salmonella have been described at a low level in the EU, nevertheless the increasing importation of poultry meat could be an important source of epidemic strains carrying ESC resistance genes. This study evaluated ESC resistance and its genetic platform among Salmonella isolates from poultry meat products imported into Portugal as well as clonal relatedness of the isolates. All Salmonella isolates recovered from samples of fresh meat destined for import into the EU in the scope of Portuguese official border control (2014–2015) were studied. Antibiotic susceptibility and β-lactamase production was determined by disk diffusion/microdilution. Molecular studies included detection of genes encoding acquired AmpC and extended-spectrum β-lactamases, plasmid-mediated quinolone resistance and other antibiotic resistance genes by PCR/sequencing, and clonality by MLST and Xba I-PFGE. Plasmid characterisation was assessed by conjugation assays, replicon typing (PCR-PBRT/pMLST) and hybridisation experiments (I- Ceu I/S1-PFGE nuclease). Isolates belonged to Salmonella Heidelberg ( n  = 6; ST15/eBG26) and Salmonella Minnesota ( n  = 1; ST548/eBG77) and presented multidrug-resistant profiles, including to ESCs and/or fluoroquinolones. All but one carried bla CMY-2 , located on two epidemic plasmids, IncA/C (ST2, n  = 5) or transferable IncI1 (ST12, n  = 1). Salmonella Heidelberg was associated with five PFGE types, including one similar to an American epidemic clone. This study reveals imported poultry products as a source of uncommon and/or invasive ESC-resistant Salmonella strains in the EU. The increase of clinically relevant poultry-related serotypes in Europe must be taken into account in the current monitoring of antibiotic resistance trends and in re-evaluation of food regulations. [ABSTRACT FROM AUTHOR]

Alterations in cefepime pharmacokinetic (PK) exposure and decreased bacterial susceptibility increase the risk of treatment failure. The impact of susceptible-dose-dependent (SDD) minimum inhibitory concentrations (MICs), i.e. 4–8 µg/mL, on target attainment rates for cefepime in febrile neutropenia (FN) is unclear. We sought to identify optimal cefepime regimens against SDD cefepime MICs in FN using a modelling and simulation approach. Creatinine clearance (CL Cr ) and body surface area (BSA) covariate-adjusted models of clearance were evaluated. Monte Carlo simulations representing 10 000 patients were completed to assess various dosing strategies (i.e. 3–8 g/day infused over 0.5–24 h, replaced every 6–24 h) and predict probabilities of target attainment (PTAs) for unbound cefepime. Nine patients received cefepime 2 g every 8 h (q8h) (0.5-h infusion). A two-compartment PK model with BSA- and CL Cr -adjusted clearance was fit to the data. Mean population values for total clearance (6.3 ± 1.1 L/h), intercompartmental clearance (6.9 ± 2.8 L/h), and central (14.8 ± 3.8 L) and peripheral (10.9 ± 4.6 L) distribution volumes were all estimated with <50% CV. Simulated dosing regimens of 3–4 g/day administered as continuous infusions and doses of 2 g administered q6h (0–5 h infusion) to q8h (4-h infusion) achieved ≥90% PTA at MICs up to 8 µg/mL. Simulated regimens of 1 g q8h (4-h infusion) or 1 g q6h (0.5-h infusion) achieved ≥90% PTA only against MICs up to 4 µg/mL. High-dose prolonged infusion or more frequent cefepime regimens may be necessary to treat FN organisms with SDD MICs. [ABSTRACT FROM AUTHOR]

The quantitative impact of severity of illness on pharmacodynamic thresholds is poorly defined. We used a robust cefepime outcomes cohort and previously identified pharmacodynamic breakpoints of 68% [pharmacokinetic (PK) model 1] and 74% (PK model 2) to probe interactions and relationships with modified Acute Physiology and Chronic Health Evaluation (mAPACHE) II scores. When the time that serum concentration remains above the minimum inhibitory concentration during the dosing interval ( f T >MIC ) was optimised, mortality was improved between mAPACHE II scores of 9–23 and 9–22 in models 1 and 2, respectively. No significant interactions were identified. These results suggest that mAPACHE II scores of 9–22 may fall within a ‘Goldilocks’ window in which hospital survival is improved among patients achieving goal f T >MIC thresholds. [ABSTRACT FROM AUTHOR]

Recent studies have found an association between piperacillin/tazobactam when added to vancomycin and acute kidney injury (AKI) risk. However, studies were limited by the small sample size and residual confounding. The aim of this study was to compare the risk of AKI with vancomycin plus piperacillin/tazobactam (VPT) versus vancomycin plus cefepime (VC) and to examine whether pre-existing renal impairment mediates the risk. This was a retrospective cohort study using electronic health records for patients admitted to two hospitals in 2012–2013. The outcome, AKI, was defined as an increase in serum creatinine level of ≥0.3 mg/dL or ≥50% from baseline. Patients were stratified by level of renal impairment as estimated by baseline creatinine clearance. Inverse probability of treatment weighting was used to balance baseline covariates between groups. Cox proportional hazards regression was used to evaluate VPT risk of AKI compared with VC. A total of 935 (17.53%) AKI cases were identified among 5335 patients receiving VPT or VC. VPT was associated with a higher risk of AKI relative to VC, with an adjusted hazard ratio (aHR) of 1.25 [95% confidence interval (CI) 1.11–1.42] in the total population and 1.70 (95% CI 1.44–2.02) in patients with normal baseline renal function. However, no elevated risk was found in patients with prior renal impairment (aHR = 0.81, 95% CI 0.65–1.01). VPT was associated with a higher risk of AKI relative to VC. The association was true in patients with normal renal function but not in those with pre-existing renal impairment. [ABSTRACT FROM AUTHOR]

In this study, the therapeutic efficacy of third-generation cephalosporins (3GCs) was compared with that of broader-spectrum β-lactams (BSBLs) [fourth-generation cephalosporins (4GCs) and carbapenems] as empirical therapy in adults with community-onset monomicrobial Enterobacteriaceae bacteraemia. Compared with those in the 3GC group ( n  = 477), a significantly higher proportion of patients in the BSBL group ( n  = 141) had initial presentation with severe sepsis or septic shock, critical illness (Pitt bacteraemia score ≥4) at bacteraemia onset and fatal co-morbidities (McCabe classification). For propensity score matching, 318 of the 477 patients in the 3GC group were matched with 106 patients in the BSBL group with the closest propensity scores on the basis of five independent predictors of 28-day mortality. After appropriate matching, no significant differences were observed in major baseline characteristics between the 3GC and BSBL groups in terms of causative micro-organism, bacteraemia severity, major source of bacteraemia, major co-morbidities and severity of co-morbidity. Consequently, the early clinical failure rate (12.9% vs. 12.3%; P  = 0.87), bacteraemia severity (Pitt bacteraemia score ≥4; 4.6% vs. 8.2%; P  = 0.17) at Day 3, and 3-day (3.8% vs . 7.5%; P  = 0.11) and 28-day (13.2% vs . 17.0%; P  = 0.33) crude mortality rates between the two groups were similar. These data suggest that the efficacy of 3GCs is similar to that of 4GCs or carbapenems when used as empirical antimicrobial therapy for community-onset Enterobacteriaceae bacteraemia. [ABSTRACT FROM AUTHOR]

As part of the multicentre Antibiotic Therapy Optimisation Study (ATHOS), minimum inhibitory concentrations (MICs) were determined for cephalosporins alone and in combination with the β-lactamase inhibitors tazobactam, clavulanic acid and avibactam against third-generation cephalosporin-resistant Escherichia coli , Klebsiella spp. and Enterobacter spp. isolates collected in German hospitals. MIC 50/90 values were 0.25–4 mg/L for cefepime/tazobactam, 0.25–2 mg/L for ceftazidime/avibactam, 0.125–0.5 mg/L for ceftaroline/avibactam, 0.5–4 mg/L for cefpodoxime/clavulanic acid and 0.25–1 mg/L for aztreonam/avibactam, depending on the underlying resistance mechanism and organism. Based on in vitro testing, β-lactam antibiotics play an important role in the treatment of infections due to β-lactamase-producing organisms. [ABSTRACT FROM AUTHOR]

In this study, the therapeutic efficacy of cefazolin was compared with that of extended-spectrum cephalosporins (ESCs) (cefotaxime, ceftriaxone and ceftazidime) as appropriate empirical therapy in adults with community-onset monomicrobial bacteraemia caused by Escherichia coli , Klebsiella spp. or Proteus mirabilis (EKP). Compared with cefazolin-treated patients ( n  = 135), significantly higher proportions of patients in the ESC treatment group ( n  = 456) had critical illness at bacteraemia onset (Pitt bacteraemia score ≥4) and fatal co-morbidities (McCabe classification). Of the 591 patients, 121 from each group were matched using propensity score matching (PSM) based on the following independent predictors of 28-day mortality: fatal co-morbidities (McCabe classification); Pitt bacteraemia score ≥4 at bacteraemia onset; initial syndrome of septic shock; and bacteraemia due to pneumonia. After appropriate PSM, no significant differences were observed in the early clinical failure rate (10.7% vs. 7.4%; P  = 0.37), the proportion of critical illness (Pitt bacteraemia score ≥4) (0% vs. 0%; P  = 1.00) and defervescence (52.6% vs. 42.6%; P  = 0.13) on Day 3 between the cefazolin and ESC treatment groups. Similarly, no significant differences were observed in the mean of time to defervescence (4.1 days vs. 4.9 days; P  = 0.15), late clinical failure rate (18.2% vs. 10.7%; P  = 0.10) and 28-day crude mortality rate (0.8% vs. 3.3%; P  = 0.37) between the two groups. These data suggest that the efficacy of cefazolin is similar to that of ESCs when used as appropriate empirical antimicrobial treatment for community-onset EKP bacteraemia. [ABSTRACT FROM AUTHOR]

Mechanisms leading to carbapenem and cephalosporin resistance were sought in Enterobacter aerogenes isolates that were highly resistant to carbapenems but had no known carbapenemase. Results were compared with recent work examining carbapenem-resistant Enterobacter cloacae . Eighteen carbapenem-resistant E. aerogenes were screened for known β-lactamase and carbapenemase genes, and novel carbapenemases were sought in whole-genome sequencing (WGS) data of the three most resistant isolates. For all isolates, ampC , ampR , ampD and the porin genes omp35 and omp36 were investigated by Sanger sequencing or from available WGS data. Expression of ampC and porin genes was measured in comparison with cephalosporin- and carbapenem-susceptible control strains by reverse transcriptase PCR, with porin translation also detected by SDS-PAGE. Loss of Omp35, primarily due to decreased transcription (up to 250×), was observed in ertapenem-resistant isolates (MICs ≥ 2 mg/L), whereas meropenem resistance (MICs ≥ 4 mg/L) was observed in those isolates also showing decreased or no production of Omp36. Loss of Omp36 was due to combinations of premature translation termination or reduced transcription. In contrast to E. cloacae , cephalosporin resistance in E. aerogenes was not associated with lesions in AmpD. High-level cefepime resistance (MIC = 32 mg/L) was caused by a novel modification in the H-10 helix of AmpC in one isolate. The differential importance of AmpD lesions in cephalosporin resistance in E. cloacae and E. aerogenes underlines the differences between these contrasting members of the Enterobacter genus. Porin loss resulted in high-level carbapenem resistance with gradual loss of Omp36, which led to high-level meropenem resistance. [ABSTRACT FROM AUTHOR]

Neisseria gonorrhoeae is the cause of the second most common sexually transmitted bacterial infection, with ca. 80 million new cases of gonorrhoea reported annually. The recent emergence of clinical isolates resistant to the last monotherapy against this bacterium, the cephalosporins, illustrates the need for new antigonococcal agents. Here we have characterised a new group of antimicrobials based on the compound resazurin that exhibits robust activity against N. gonorrhoeae in vitro. Resazurin inhibits the growth of a broad range of N. gonorrhoeae isolates, including those resistant to multiple antibiotics. Furthermore, treatment of human endometrial cells infected with N. gonorrhoeae with resazurin significantly reduces the number of intracellular bacteria. Whilst resazurin exhibited potent in vitro antimicrobial activity, in vivo resazurin did not limit the colonisation of mice with N. gonorrhoeae following vaginal infection. The ineffectiveness of resazurin in vivo is likely due to its interaction with serum albumin, which completely diminishes its antimicrobial activity. However, treatment of mice with a resazurin analogue (resorufin pentyl ether) that maintains its antimicrobial activity in the presence of serum albumin approached a significant decrease in the percentage of mice vaginally colonised. This treatment also decreased vaginal colonisation by N. gonorrhoeae over time. Together, these data suggest that resazurin derivatives have potential for the treatment of gonorrhoea. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the evolution with time of ceftiofur-resistant Escherichia coli clinical isolates from pigs in Québec, Canada, between 1997 and 2012 with respect to pathotypes, clones and antimicrobial resistance. Eighty-five ceftiofur-resistant E. coli isolates were obtained from the OIE (World Organisation for Animal Health) Reference Laboratory for Escherichia coli . The most prevalent pathovirotypes were enterotoxigenic E. coli (ETEC):F4 (40%), extraintestinal pathogenic E. coli (ExPEC) (16.5%) and Shiga toxin-producing E. coli (STEC):F18 (8.2%). Susceptibility testing to 15 antimicrobial agents revealed a high prevalence of resistance to 13 antimicrobials, with all isolates being multidrug-resistant. bla CMY-2 (96.5%) was the most frequently detected β-lactamase gene, followed by bla TEM (49.4%) and bla CTX-M (3.5%). Pulsed-field gel electrophoresis (PFGE) applied to 45 representative E. coli isolates revealed that resistance to ceftiofur is spread both horizontally and clonally. In addition, the emergence of extended-spectrum β-lactamase-producing E. coli isolates carrying bla CTX-M was observed in 2011 and 2012 in distinct clones. The most predominant plasmid incompatibility (Inc) groups were IncFIB, IncI1, IncA/C and IncFIC. Resistance to gentamicin, kanamycin and chloramphenicol as well as the frequency of bla TEM and IncA/C significantly decreased over the study period, whereas the frequency of IncI1 and multidrug resistance to seven antimicrobial categories significantly increased. These findings reveal that extended-spectrum cephalosporin-resistant porcine E. coli isolates in Québec belong to several different clones with diverse antimicrobial resistance patterns and plasmids. Furthermore, bla CMY-2 was the major β-lactamase gene in these isolates. From 2011, we report the emergence of bla CTX-M in distinct clones. [ABSTRACT FROM AUTHOR]

Third-generation cephalosporins (3GCs) [ceftriaxone (CRO) and cefotaxime (CTX)] have remarkable potency against Enterobacteriaceae and are commonly prescribed for the treatment of community-onset bacteraemia. However, clinical evidence supporting the updated interpretive criteria of the Clinical and Laboratory Standards Institute (CLSI) is limited. Adults with community-onset monomicrobial Enterobacteriaceae bacteraemia treated empirically with CRO or CTX were recruited. Clinical information was collected from medical records and CTX MICs were determined using the broth microdilution method. Eligible patients ( n = 409) were categorised into de-escalation (260; 63.6%), no switch (115; 28.1%) and escalation (34; 8.3%) groups according to the type of definitive antibiotics. Multivariate regression revealed five independent predictors of 28-day mortality: fatal co-morbidities based on McCabe classification [odds ratio (OR) = 19.96; P < 0.001]; high Pitt bacteraemia score (≥4) at bacteraemia onset (OR = 13.91; P < 0.001); bacteraemia because of pneumonia (OR = 5.45; P = 0.007); de-escalation after empirical therapy (OR = 0.28; P = 0.03); and isolates with a CTX MIC ≤ 1 mg/L (OR = 0.17; P = 0.02). Of note, isolates with a CTX MIC ≤ 8 mg/L (indicated as susceptible by previous CLSI breakpoints) were not associated with mortality. Furthermore, clinical failure and 28-day mortality rates had a tendency to increase with increasing CTX MIC ( γ = 1.00; P = 0.01). Conclusively, focusing on patients with community-onset Enterobacteriaceae bacteraemia receiving empirical 3GC therapy, the present study provides clinically critical evidence to validate the proposed reduction in the susceptibility breakpoint of CTX to MIC ≤ 1 mg/L. [ABSTRACT FROM AUTHOR]

Complicated intra-abdominal infection (cIAIs) are a common and important cause of morbidity worldwide. In this study, the clinical features, microbiological profiles, antimicrobial patterns and treatments of 3233 cIAI patients (mean age, 47.6 years; 54.7% male) with 3531 hospitalisations from 2008–2013 were retrospectively investigated. The most commonly isolated bacteria were Escherichia coli (47.6%), Klebsiella pneumoniae (16.9%), Enterococcus faecalis (10.4%) and Pseudomonas aeruginosa (8.8%). Ciprofloxacin, aminoglycoside (gentamicin), piperacillin/tazobactam and carbapenems exhibited activity against 53%, 76%, 88% and 100% of extended-spectrum β-lactamase (ESBL)-positive Enterobacteriaceae isolates, respectively. Pseudomonas aeruginosa isolates exhibited 100%, 95%, 88%, 71% and 76% susceptibility to aminoglycoside (gentamicin), ciprofloxacin, meropenem, imipenem and ceftazidime, respectively, and Enterococcus remained 100% susceptible to vancomycin and linezolid. β-Lactam antibacterials other than penicillin (specifically third-generation cephalosporins) and imidazole derivatives (ornidazole and metronidazole) were the most common first-line treatments. Patients subjected to regimen change after initial antibiotic treatment had predisposing conditions (e.g. older age, more severe co-morbidities) and a higher incidence of P. aeruginosa infection; in addition, these patients encountered a higher average cost of care and worse clinical outcomes compared with those without medication modification. Taken together, these findings indicate the importance of appropriate initial empirical therapy and suggest the use of combination therapy comprising cephalosporins and metronidazole. [ABSTRACT FROM AUTHOR]

Escherichia coli recovered from three hospitals in Barcelona (Spain) were studied to determine the prevalence of isolates with acquired AmpC (ac-AmpC) and/or overproduced chromosomal AmpC (c-AmpC). Mechanisms involved in bla c-AmpC overexpression, bla ac-AmpC and the plasmids associated with their distribution as well as the prevalence of plasmid-mediated quinolone resistance (PMQR) in AmpC-producing isolates were also determined. Isolates were selected according to their resistance phenotype. bla ac-AmpC , alterations in the bla c-AmpC promoter/attenuator, and PMQR genes [ qnrA , qnrB , qnrS , aac(6′)-Ib -cr and qepA ] were characterised by PCR and sequencing. bla c-AmpC expression was determined by qRT-PCR. Population structure analysis was performed using PFGE, MLST and phylogenetic group PCR. Plasmids carrying bla ac-AmpC were characterised by PCR-based replicon typing and S1-PFGE. IncI1 and IncF plasmids were also analysed by plasmid MLST and replicon sequence typing, respectively. Among 21 563 E. coli isolates, 240 (1.1%) overproduced AmpC β-lactamases, including 180 (75.0%) harbouring ac-AmpC (132 CMY-2 variants and 48 DHA-1) and 60 (25.0%) c-AmpC enzymes. Three mutation profiles in the bla c-AmpC promoter/attenuator were associated with a 72.5-, 19.9- and 5.8-fold increased expression, respectively. Moreover, 63.3% of ac-AmpC and 43.3% of c-AmpC isolates belonged to B2, D, E or F phylogenetic groups. PMQR was found in 31% of ac-AmpC isolates [38 qnrB4 , 8 aac(6′)-Ib -cr, 6 qnrS1 and 3 qnrB19 ] and in 10% of c-AmpC isolates [5 aac(6′)-Ib -cr and 1 qnrS1 ]. IncI1-ST12 and IncF were associated with bla CMY-2 and bla DHA-1 , respectively. These results suggest that ac-AmpC β-lactamases were the main mechanism of AmpC production. Isolates and plasmids both showed high genetic diversity. [ABSTRACT FROM AUTHOR]

Drug-resistant Neisseria gonorrhoeae has become a global health concern that requires immediate attention. Due to increasing resistance to cephalosporins, pursuing novel alternatives for treating N. gonorrhoeae infections is paramount. Whilst new drug development is often cumbersome, reviving antiquated antibiotic agents for treatment of modern infections has become prevalent in clinical practice. Fosfomycin exhibits bactericidal activity through a unique mechanism of action, and a variety of organisms including N. gonorrhoeae are susceptible. In vitro studies have demonstrated that fosfomycin can retain activity against ceftriaxone-resistant N. gonorrhoeae ; however, it remains unclear whether there is synergy between fosfomycin and other antibiotics. Clinical investigations evaluating fosfomycin for the treatment of N. gonorrhoeae infections are confounded by methodological limitations, none the less they do provide some perspective on its potential role in therapy. Future studies are needed to establish a safe, convenient and effective fosfomycin regimen for treating N. gonorrhoeae infections. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effect of dexamethasone in combination with low-dose or high-dose daptomycin for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis. Efficacy (ΔCFU/mL) and cerebrospinal fluid (CSF) levels of daptomycin at 15 mg/kg and 25 mg/kg were studied in a rabbit model of pneumococcal meningitis, comparing them with the same doses in combination with dexamethasone at 0.125 mg/kg every 12 h over a 26-h period against two different Streptococcus pneumoniae strains, HUB 2349 and ATCC 51916 with daptomycin minimum inhibitory concentrations (MICs) of 0.09 mg/L and 0.19 mg/L, respectively. Daptomycin levels in CSF were lower when dexamethasone was given concurrently. Against strain HUB 2349, therapeutic failure occurred with daptomycin 15 mg/kg + dexamethasone; daptomycin 25 mg/kg + dexamethasone was better at reducing bacterial counts than the lower dose throughout treatment. Against the highly cephalosporin-resistant ATCC 51916 strain, daptomycin 15 mg/kg + dexamethasone achieved a lower bacterial decrease than daptomycin 15 mg/kg alone, and therapeutic failure at 24 h occurred in the daptomycin 15 mg/kg + dexamethasone group. Addition of dexamethasone to a 25 mg/kg daptomycin dose did not affect the efficacy of daptomycin: it remained bactericidal throughout treatment. In conclusion, against the studied strains, low-dose (15 mg/kg/day) daptomycin is affected by concomitant use of dexamethasone: CSF levels are reduced and its bacterial efficacy is affected. At a higher daptomycin dose (25 mg/kg/day), however, the use of dexamethasone does not alter efficacy; the combination appears to be a good choice for the treatment of pneumococcal meningitis. [ABSTRACT FROM AUTHOR]

Gatherings like the Hajj involving many people who travel from different parts of the world represent a risk for the acquisition and dissemination of infectious diseases. In this study, acquisition of multidrug-resistant (MDR) Salmonella spp. in 2013 Hajj pilgrims from Marseille, France, was investigated. In total, 267 rectal swabs were collected from 129 participants before their departure and after their return from the pilgrimage as well as during the pilgrimage from patients with diarrhoea. Samples were screened for the presence of Salmonella using quantitative real-time PCR and culture. Whole-genome sequencing was performed to characterise one of the isolates, and the mechanism leading to colistin resistance was investigated. Six post-Hajj samples and one sample collected during a diarrhoea episode in Hajj were positive for Salmonella by real-time PCR, with five Salmonella enterica belonging to several serotypes recovered by culture, whereas no pre-Hajj sample was positive. Two of the isolates belonged to the epidemic Newport serotype, were resistant to cephalosporins, gentamicin and colistin, and harboured the bla CTX-M-2 gene and a 12-nucleotide deletion in the pmrB gene leading to colistin resistance. This study shows that pilgrims acquired Salmonella bacteria, including a novel MDR clone, during the Hajj pilgrimage. This calls for more improved public health surveillance during Hajj because Salmonella is one of the most common diarrhoea-causing bacteria worldwide. Therefore, returning pilgrims could disseminate MDR bacteria worldwide upon returning to their home countries. [ABSTRACT FROM AUTHOR]

Multidrug resistance is quite common among non-fermenting Gram-negative rods, in particular among clinically relevant species including Pseudomonas aeruginosa and Acinetobacter baumannii. These bacterial species, which are mainly nosocomial pathogens, possess a diversity of resistance mechanisms that may lead to multidrug or even pandrug resistance. Extended-spectrum β-lactamases (ESBLs) conferring resistance to broad-spectrum cephalosporins, carbapenemases conferring resistance to carbapenems, and 16S rRNA methylases conferring resistance to all clinically relevant aminoglycosides are the most important causes of concern. Concomitant resistance to fluoroquinolones, polymyxins (colistin) and tigecycline may lead to pandrug resistance. The most important mechanisms of resistance in P. aeruginosa and A. baumannii and their most recent dissemination worldwide are detailed here. [ABSTRACT FROM AUTHOR]

Ceftaroline is a novel cephalosporin with activity against Gram-positive organisms, including meticillin-resistant Staphylococcus aureus (MRSA). The objective of this study was to investigate the susceptibility to ceftaroline of hospital-associated MRSA (HA-MRSA) isolates causing acute bacterial skin and skin-structure infections (ABSSSIs) in China and to examine their relationship by genotyping. A total of 251 HA-MRSA isolates causing ABSSSIs were collected from a multicentre study involving 56 hospitals in 38 large cities across 26 provinces in mainland China. All isolates were characterised by multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCC mec ) typing, spa typing and detection of the Panton–Valentine leukocidin locus ( lukS-PV and lukF-PV ). Minimum inhibitory concentrations (MICs) of 14 antimicrobial agents, including ceftaroline, were determined by broth microdilution and were interpreted using Clinical and Laboratory Standards Institute breakpoints. The ceftaroline MIC 50 and MIC 90 values (MICs that inhibit 50% and 90% of the isolates, respectively) were 1 μg/mL and 2 μg/mL, respectively; 33.5% ( n = 84) of the isolates studied were ceftaroline-non-susceptible, with MICs of 2 μg/mL, but no isolate exhibited ceftaroline resistance (MIC > 2 μg/mL). All of the ceftaroline-non-susceptible isolates belonged to the predominant HA-MRSA clones: 95.2% ( n = 80) from MLST clonal complex 8 (CC8), with the remaining 4.8% ( n = 4) from CC5. The high rate of non-susceptibility to ceftaroline amongst HA-MRSA causing ABSSSIs in China is concerning. [ABSTRACT FROM AUTHOR]

In response to antimicrobial resistance of Neisseria gonorrhoeae to last-resort extended-spectrum cephalosporins, combination therapy of azithromycin + ceftriaxone is now recommended. Dual therapy can be effective to treat monoresistant strains as well as multidrug-resistant strains, preferably employing the effect of in vitro synergy. As reports on in vitro synergy of azithromycin + ceftriaxone in N. gonorrhoeae are conflicting, in this study an evaluation of this combination was performed using a cross-wise Etest method and agar dilution. Synergy was defined as a fractional inhibitory concentration index (FICI) of ≤0.5. To identify other dual treatment options for gonorrhoea, in vitro synergy was evaluated for 65 dual antimicrobial combinations using Etest. Azithromycin, cefixime, ceftriaxone, colistin, ertapenem, fosfomycin, gentamicin, minocycline, moxifloxacin, rifampicin, spectinomycin and tigecycline were screened for synergy in all possible combinations. No synergy or antagonism was found for any of the 65 combinations. The geometric mean FICI ranged from 0.82 to 2.00. The mean FICI of azithromycin + ceftriaxone was 1.18 (Etest) and 0.55 (agar dilution). The difference between both methods did not result in a difference in interpretation of synergy. Ceftriaxone-resistant strain F89 was tested in all combinations and no synergy was found for any of them. Most importantly, the ceftriaxone minimum inhibitory concentration of F89 was not decreased below the breakpoint with any concentration of azithromycin. [ABSTRACT FROM AUTHOR]

Previous in vivo studies using a human-simulated regimen of ceftaroline/avibactam 600/600 mg every 8 h (q8h) showed activity against extended-spectrum β-lactamase-, AmpC- and KPC-producing Enterobacteriaceae with minimum inhibitory concentrations (MICs) ≤1 μg/mL. Here we sought to determine the efficacy of this human-simulated regimen against organisms with MICs ≥1 μg/mL to help determine a breakpoint value that would reliability predict efficacy in humans. In total, 31 isolates (1 Escherichia coli , 9 Klebsiella pneumoniae , 9 Enterobacter cloacae , 1 Citrobacter koseri , 2 Serratia marcescens , 1 Klebsiella oxytoca and 8 Pseudomonas aeruginosa ) with ceftaroline/avibactam MICs of 1 to 16 μg/mL were tested in a murine immunocompromised thigh infection model; 15 isolates were also tested in an immunocompetent model. Doses were given to simulate human free drug exposures of ceftaroline fosamil/avibactam 600/600 mg q8h over 24 h as a 1-h infusion by targeting the f T >MIC profile. Efficacy was evaluated as the change in log 10 CFU compared with 0-h controls after 24 h. Reductions in bacterial CFU in the neutropenic model were seen against a majority of isolates tested with MICs ≤4 μg/mL, where f T >MIC was >55%. More variable efficacy was seen in isolates with MICs ≥8 μg/mL, where f T >MIC drops below 40%. Overall activity was enhanced in the immunocompetent model. The humanised regimen of ceftaroline fosamil/avibactam 600/600 mg q8h as a 1-h infusion showed predictable efficacy against isolates with various genotypic and phenotypic profiles and MICs ≤4 μg/mL. These data provide valuable information to help determine a ceftaroline/avibactam breakpoint for Enterobacteriaceae. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the comparative effectiveness and safety of antistaphylococcal penicillins (ASPs) and cephalosporins for the definitive treatment of patients with meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia. PubMed and Scopus electronic databases were searched up to December 2013. All-cause mortality was the primary outcome of interest. A meta-analysis of unadjusted and adjusted data was performed. Seven articles (1643 patients) were included; all but one were retrospective studies, and three of them employed propensity score matching. The studies enrolled primarily adults hospitalised in medical wards for primary or secondary community-acquired, healthcare-associated or nosocomial MSSA bacteraemia. Several ASPs and cephalosporins were compared. Unadjusted 30-day mortality was lower in patients treated with ASPs than in those treated with cephalosporins [risk ratio (RR) = 0.62, 95% confidence interval (CI) 0.40–0.98]. Propensity score-adjusted 30-day mortality was not different in patients receiving ASPs or cephalosporins (RR = 0.75, 95% CI 0.41–1.39). Substantial heterogeneity and publication bias were found in these analyses. Both unadjusted (RR = 0.85, 95% CI 0.54–1.32) and adjusted (RR = 1.42, 95% CI 0.22–9.06) 90-day mortality did not differ between patients receiving ASPs or cephalosporins. Limited data regarding adverse events, development of resistance and recurrence were available. In conclusion, the limited available published data derive from retrospective studies and show that there appears to be no statistically significant difference in mortality between ASPs and cephalosporins for the treatment of MSSA bacteraemia. [ABSTRACT FROM AUTHOR]

• Pyelonephritis treatment may need to be reconsidered due to rising resistance rates. • Outcomes were compared between oral cephalosporins and first-line agents. • Urinary tract infection (UTI) recurrence rates were not different between groups. • Independent risk factors for UTI recurrence were chronic kidney disease and Klebsiella spp. Fluoroquinolones and trimethoprim/sulfamethoxazole (TMP-SMX) are first-line agents for acute pyelonephritis. Oral β-lactams are second-line agents owing to reported lower efficacy rates, primarily seen with aminopenicillins rather than cephalosporins. The increase in resistance rates and adverse effects associated with first-line agents provides justification to reconsider oral cephalosporins for pyelonephritis. Therefore, the objective of this study was to determine whether there is a difference in urinary tract infection (UTI) recurrence rates between oral cephalosporins and first-line agents in the treatment of acute pyelonephritis. This was a retrospective, single-centre, observational cohort study from 1 December 2018 to 31 May 2020. The study population was adult TRICARE beneficiaries with a diagnosis of acute pyelonephritis who were treated with oral antibiotics. The two cohorts compared were first-line antibiotics (ciprofloxacin, levofloxacin and TMP-SMX) and oral cephalosporins. The primary outcome was UTI recurrence rate at 30 days, which was defined as a repeat clinic visit, emergency department visit or hospital admission for a UTI (cystitis or pyelonephritis). The secondary outcome was to determine independent risk factors for UTI recurrence. A total of 268 cephalosporin and 211 first-line cases were included. The primary composite outcome of UTI recurrence within 30 days occurred in 44 (16%) cephalosporin and 36 (17%) first-line cases (P = 0.851). Independent risk factors for UTI recurrence were chronic kidney disease and Klebsiella spp. isolation. In conclusion, there was no significant difference in UTI recurrence rates between oral cephalosporins and first-line agents in the treatment of acute pyelonephritis in the outpatient setting. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance in Neisseria gonorrhoeae has severely limited the number of treatment options, and the emergence of extended-spectrum cephalosporin resistance threatens the effectiveness of the last remaining recommended treatment regimen. This study assessed the in vitro susceptibility of N. gonorrhoeae to ETX0914, a novel spiropyrimidinetrione that inhibits DNA biosynthesis. In vitro activity was determined by agar dilution against 100 N. gonorrhoeae isolates collected from men presenting with urethritis in the USA during 2012–2013 through the Gonococcal Isolate Surveillance Project. The minimum inhibitory concentration (MIC) that inhibited growth in 50% (MIC 50 ) and 90% (MIC 90 ) of isolates was calculated for each antimicrobial agent. ETX0914 demonstrated a high level of antimicrobial activity against N. gonorrhoeae , including isolates with decreased susceptibility or resistance to currently available agents. The ability of ETX0914 to inhibit the growth of N. gonorrhoeae was similar to ceftriaxone, which is currently recommended in combination with azithromycin to treat gonorrhoea. The data presented in this study strongly suggest that ETX0914 should be evaluated in a clinical trial for the treatment of N. gonorrhoeae . [ABSTRACT FROM AUTHOR]

Abstract: This study aimed to detect and characterise clinical Escherichia coli isolates suspected of carrying chromosomally encoded CTX-M enzymes. Escherichia coli (n =356) obtained in Germany, The Netherlands and the UK (2005–2009) and resistant to third-generation cephalosporins were analysed for the presence of ESBL-/AmpC-encoding genes within the European SAFEFOODERA-ESBL project. β-Lactamases and their association with IS26 and ISEcp1 were investigated by PCR. Isolates were typed by phylogenetic grouping, MLST and PFGE. Plasmids were visualised by S1 nuclease PFGE, and the location of bla CTX-M genes was determined by Southern hybridisation of XbaI-, S1- and I-CeuI-digested DNA. ESBL enzymes could not be located on plasmids in 17/356 isolates (4.8%). These 17 isolates, from different countries and years, were ascribed to phylogenetic groups D (9), B2 (6) and B1 (2), and to seven sequence types, with ST38 being the most frequent (7 phylogroup D isolates). Eleven isolates produced CTX-M-15. bla CTX-M-15 genes were associated with ISEcp1. The remaining isolates expressed the CTX-M group 9 β-lactamases CTX-M-14 (4), CTX-M-9 (1) and CTX-M-51 (1). bla CTX-M probes hybridised with I-CeuI- and/or XbaI-digested DNA, but not with S1-digested DNA, corroborating their chromosomal location. To summarise, only 4.8% of a large collection of ESBL-producing E. coli isolates harboured chromosomal bla CTX-M genes. These isolates were of human origin and belonged predominantly to ST38 and ST131, which possibly indicates the role of these sequence types in this phenomenon. However, heterogeneity among isolates was found, suggesting that their spread is not only due to the dispersion of successful E. coli clones. [Copyright &y& Elsevier]

Abstract: During 2012, a total of 2968 isolates were consecutively collected from 59 medical centres in the USA and 15 European countries from hospitalised patients with pneumonia. Ceftolozane/tazobactam (tazobactam at a fixed concentration of 4mg/L) and comparator agents were tested by reference methods, and MIC endpoints were interpreted by CLSI (2013) and EUCAST (2013) breakpoint criteria. Pseudomonas aeruginosa was the most common isolated pathogen (1019 strains; 34.3%), and ceftolozane/tazobactam was the most active β-lactam tested against P. aeruginosa (MIC50/90, 0.5/4mg/L; 94.1% inhibited at ≤8mg/L). P. aeruginosa exhibited moderate susceptibility to meropenem (MIC50/90, 0.5/>8mg/L; 73.7% susceptible), ceftazidime (MIC50/90, 2/>32mg/L; 73.6% susceptible), cefepime (MIC50/90, 4/>16mg/L; 76.5% susceptible), piperacillin/tazobactam (MIC50/90, 8/>64mg/L; 69.5% susceptible), levofloxacin [MIC50/90, 0.5/>4mg/L; 69.9/61.0% susceptible (CLSI/EUCAST criteria)] and gentamicin (MIC50/90, 2/>8mg/L; 80.7% susceptible). Ceftolozane/tazobactam exhibited activity against many ceftazidime-non-susceptible, meropenem-non-susceptible and piperacillin/tazobactam-non-susceptible, multidrug-resistant (MDR) and extensively drug-resistant (XDR) P. aeruginosa isolates. Ceftolozane/tazobactam was active (MIC50/90, 0.25/4mg/L; 94.6% inhibited at ≤8mg/L) against 1530 Enterobacteriaceae, including activity against many MDR and XDR strains. MDR and XDR prevalence varied widely between countries both for P. aeruginosa (24.1% MDR and 17.1% XDR overall) and Enterobacteriaceae (15.4% MDR and 2.7% XDR overall). All β-lactams had limited activity against Acinetobacter spp. and Stenotrophomonas maltophilia. Ceftolozane/tazobactam demonstrated greater in vitro activity than currently available cephalosporins, carbapenems and piperacillin/tazobactam when tested against P. aeruginosa. In addition, ceftolozane/tazobactam demonstrated greater activity than contemporary cephalosporins and piperacillin/tazobactam when tested against most Enterobacteriaceae. [Copyright &y& Elsevier]

Abstract: Resistance to third-generation cephalosporins (3GCs) mediated by extended-spectrum β-lactamases (ESBLs) in pathogenic Enterobacteriaceae is considered a major public health threat in India. This study deals with the detection of plasmid-mediated bla CTX-M, bla SHV and bla OXA genes, understanding their contribution to the ESBL phenotype, and their molecular interaction with 3GCs. More than 87% of isolates showed 3GC resistance, with ESBL production in 60.0% of Escherichia coli and 47.7% of Klebsiella pneumoniae. Molecular characterisation revealed the presence of bla CTX-M-15 (29.8%), bla CTX-M-truncated (1.3%), bla CTX-M-27 (0.7%), bla SHV-1 (20.5%), bla SHV-11 (2.0%), bla SHV-42 (0.7%) and bla OXA-1 (9.9%), among which bla CTX-M variants and bla SHV-42 were ESBLs. Phylogenetic analysis predicted strong selection pressure on all bla CTX-M variants, bla SHV-11 and bla SHV-42. The instability index and Gibbs free folding energy change (ΔΔG) predicted decreased stability of SHV-11 and SHV-42. Mutations of CTX-M-truncated, SHV-11 and SHV-42 located in the core region of the enzymes were found to be functional/pathogenic in nature. The catalytic pockets of CTX-M-15 and SHV-42 had the greatest molecular surface area, which might explain their expanded substrate spectrum towards oxyimino-cephalosporins. Molecular dynamics analysis indicated different structural flexibility of CTX-M-truncated compared with the other enzymes. Amino acid alterations resulted in a change of orientation of catalytic residues of class A β-lactamases that might affect their catalytic processes. Molecular interactions revealed higher catalytic efficiency (ΔG and K m ) of CTX-M-15, CTX-M-truncated, CTX-M-27, SHV-11 and SHV-42 compared with their respective wild-types. This study provides useful insights into ESBL production of pathogenic Enterobacteriaceae in India that might help in the development of new antibiotics. [Copyright &y& Elsevier]

Abstract: Based on the new recommendations of the Clinical and Laboratory Standards Institute (CLSI), the revised cephalosporin breakpoints may result in many CTX-M-producing Escherichia coli being reported as susceptible to ceftazidime. We determined the activity of ceftazidime and other parenteral β-lactam agents in standard- and high-inoculum minimum inhibitory concentration (MIC) tests against CTX-M-producing E. coli isolates. Antimicrobial susceptibility was determined using a broth microdilution MIC method with inocula that differed 100-fold in density. An inoculum effect was defined as an eight-fold or greater increase in MIC on testing with the higher inoculum. When the revised CLSI ceftazidime breakpoint of 4μg/mL was applied, 34 (34.3%) of the 99 CTX-M-producers tested were susceptible. More specifically, for 42 CTX-M-14-producing E. coli isolates, 32 (76.2%) were susceptible at 4μg/mL. Cefotaxime, ceftazidime, cefepime and piperacillin/tazobactam were found to be associated with inoculum effects in 100% of the evaluable tests for extended-spectrum β-lactamase-producing E. coli isolates. The MIC50 (MIC required to inhibit 50% of isolates) of ceftazidime was 16μg/mL in the standard-inoculum tests and >512μg/mL in the high-inoculum tests. In the high-inoculum tests including isolates encoding CTX-M-14, ceftazidime was dramatically affected, with susceptibility decreasing from 82.1% of isolates inhibited at 4μg/mL in the standard-inoculum tests to 0% at high inoculum. Although further studies may demonstrate that ceftazidime has a role in the treatment of infections caused by these organisms, we suggest that until more data become available, clinicians should be cautious about treating serious CTX-M-producing E. coli infections with ceftazidime or cefepime. [Copyright &y& Elsevier]

Abstract: Antibiotic stewardship is universally agreed to be desirable, but optimal models for stewardship remain uncertain. UK stewardship targets the particular antibiotic families—cephalosporins and fluoroquinolones—blamed for the selection of Clostridium-difficile-associated disease. To balance this there have been dramatic increases in the use of penicillin–β-lactamase inhibitor combinations. By channelling selection pressure in this way, we hazard destroying the utility of these antibiotic classes in turn, as happened with gonorrhoea where penicillins, fluoroquinolones and cefixime were sequentially lost as therapies. Strikingly, in context, almost all carbapenemase-producers are highly resistant to penicillin–β-lactamase inhibitor combinations, which may select for them. There is an urgent need to explore an alternative stewardship model, seeking to limit total antibiotic use but to maintain heterogeneity in what is used, avoiding concentrated selection pressure. There is also a great need to improve and accelerate diagnostics for infection and resistance, reducing or removing the need for protracted empirical treatment with broad-spectrum agents. [Copyright &y& Elsevier]

Abstract: Ceftobiprole is a broad-spectrum cephalosporin with activity against methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative pathogens including Pseudomonas aeruginosa. The aim of this study was to evaluate the activity of ceftobiprole against MRSA isolates with decreased susceptibility to daptomycin, linezolid or vancomycin as well as isolates from staphylococcal chromosome cassette mec (SCCmec) types I, II, III and IV. Overall, ceftobiprole demonstrated high potency against the 216 isolates tested, with MIC50 and MIC90 values (minimum inhibitory concentrations required to inhibit 50% and 90% of the isolates, respectively) of 1mg/L and 2mg/L (97.2% susceptible). The MIC90 for ceftobiprole was 2mg/L against the linezolid-non-susceptible, daptomycin-non-susceptible and vancomycin-intermediate (VISA and hVISA) subsets and was 1mg/L against the vancomycin-resistant (VRSA) strains. The MIC50/90 values for ceftobiprole were 2/4, 1/2, 2/2 and 1/1mg/L against SCCmec types I, II, III and IV, respectively. SCCmec type I strains had the highest MICs, with six strains exhibiting a ceftobiprole MIC of 4mg/L and 15 strains at 2mg/L. Ceftobiprole demonstrated potent activity against MRSA, including subsets of isolates with reduced susceptibility to daptomycin, linezolid and vancomycin. The activity of ceftobiprole against these resistant phenotypes indicates that it may have clinical utility in the treatment of infections caused by multidrug-resistant S. aureus and across strains from prevalent SCCmec types. [Copyright &y& Elsevier]

Abstract: The aim of this study was to identify genes conferring resistance to fluoroquinolones and extended-spectrum β-lactams in non-typhoidal Salmonella (NTS) from food-producing animals in China. In total, 31 non-duplicate NTS were obtained from food-producing animals that were sick. Isolates were identified and serotyped and the genetic relatedness of the isolates was determined by pulsed-field gel electrophoresis of XbaI-digested chromosomal DNA. Antimicrobial susceptibility was determined using Clinical and Laboratory Standards Institute methodology. The presence of extended-spectrum β-lactamase (ESBL) and fluoroquinolone resistance genes was established by PCR and sequencing. Genes encoded on transmissible elements were identified by conjugation and transformation. Plasmids were typed by PCR-based replicon typing. The occurrence and diversity of numerous different transmissible genes conferring fluoroquinolone resistance [qnrA, qnrD, oqxA and aac(6′)-Ib-cr] and ESBLs (CTX-M-27 and CTX-M-14), and which co-resided in different isolates and serovars of Salmonella, were much higher than in European countries. Furthermore, different plasmids encoded fluoroquinolone resistance (ca. 6kb) and β-lactam resistance (ca. 63kb) and these co-resided in isolates with mutations in topoisomerase genes (gyrA and parC) giving very resistant Salmonella. The presence of multidrug-resistant bacteria in food-producing animals in countries that export foodstuffs suggests that global transfer of antibiotic resistances from country to country on food is possible. [Copyright &y& Elsevier]

Abstract: The aim of this study was to evaluate the in vitro efficacy of ceftobiprole and comparator antibiotics, either alone or in combination, in staphylococcal MBEC™ (minimum biofilm eradication concentration) and colony biofilm assays at dilutions of the maximum free-drug plasma concentration attained during clinical use (fC max). Staphylococci tested included meticillin-susceptible and meticillin-resistant Staphylococcus aureus (n =6) and Staphylococcus epidermidis (n =2). Relative to no-drug controls, after 7 days of exposure ceftobiprole concentrations from 1/4 fC max to fC max generally decreased CFUs in MBEC or colony biofilms of S. aureus isolates by ca. 1.5log10 to ≥2.5log10. Gentamicin reduced colony biofilm CFUs by ≥1.4log10 at these concentrations with gentamicin-susceptible isolates. Following 7 days of exposure, vancomycin and rifampicin were ineffective as single agents or in combination in the colony model, but yielded CFU decreases from 0 to 5log10 in the MBEC model. Treatment of biofilms with rifampicin for 7 days yielded rifampicin-resistant mutants, and the selection of rifampicin resistance was inhibited by co-treatment with ceftobiprole. Thus, ceftobiprole alone or in combination demonstrated promising activity against biofilms of meticillin-susceptible and -resistant staphylococci at clinically relevant concentrations. In contrast, vancomycin and rifampicin, two agents used clinically for the treatment of biofilm infections, tested separately or together gave inconsistent results and generally had little impact on cell viability. [Copyright &y& Elsevier]

Abstract: The aim of this study was to uncover the mechanisms underlying Shigella flexneri resistance to cefalothin. In this study, a resistance-related S. flexneri isolate, S. flexneri YDC, was obtained from S. flexneri mel-1998023/zz pre-incubated with cefalothin at a dose of 0.5× the minimum inhibitory concentration. The ISEcp1 coding element was identified upstream of bla CTX-M-55 in S. flexneri YDC. To further determine the role of ISEcp1 in S. flexneri resistance, plasmids containing bla CTX-M-55 recombinant with or without the ISEcp1 sequence were constructed and named as pCTX and pISECTX, respectively. It was shown that Escherichia coli DH5α(pISECTX) was resistant to all β-lactams tested. In contrast, E. coli DH5α(pCTX) was sensitive to all except β-lactams cefazolin and cefalothin. In addition, reverse transcription PCR showed that expression levels of bla CTX-M-55 were higher in E. coli DH5α(pISECTX). The Clinical and Laboratory Standards Institute (CLSI) assay demonstrated that extended-spectrum β-lactamase was only positively detected in E. coli DH5α(pISECTX) but not in E. coli DH5α(pCTX). Taken together, these results suggest that the translocated ISEcp1 element upstream of bla CTX-M-55 is required for overexpression of bla CTX-M-55, leading to cephalosporin resistance. [Copyright &y& Elsevier]

Abstract: Data regarding ceftaroline use for meticillin-resistant Staphylococcus aureus bacteraemia (MRSAB) are lacking. Here we review the outcomes of 31 patients with MRSAB treated with ceftaroline, including 9 patients with endocarditis. Clinical success was observed in 23 patients (74.2%). Adverse events associated with prolonged therapy were rare and included eosinophilic pneumonia, rash and diarrhoea. We conclude that ceftaroline can be used for MRSAB. [Copyright &y& Elsevier]

• Over 220 TEM variants observed to date originated from two major mutant clones. • One began with the Gly238Ser change and the other originated with the Arg164Ser substitution. • These two first-step mutants led to stepwise alteration in enzyme structure and activity. • Dissemination of strains producing TEM-1 variants underlies the markedly increased prevalence of β-lactam resistance. The TEM-1 β-lactamase can only cleave penicillin and the first-generation cephalosporins but it has evolved to become active against second-, third- and fourth-generation drugs. Through sequence analysis of natural TEM variants and those created by mutagenesis experiments, we described two distinct evolution routes of TEM-1 that has generated over 220 enzyme variants. One began with the Gly238Ser alteration and the other originated with the Arg164Ser substitution. Further acquisition of mutations in the background of each of these two first-step mutants led to stepwise alteration in enzyme structure and hence activity, eventually producing a wide range of enzyme variants whose substrate specificities cover cephalosporins of all generations. Dissemination of strains producing TEM-1 variants generated from these two evolution routes underlies the markedly increased prevalence of bacterial resistance to β-lactams in the past few decades. This study provides insights into the evolution of hydrolysing enzymes, in particular β-lactamases. [ABSTRACT FROM AUTHOR]

Abstract: Early appropriate antibiotic treatment reduces mortality in severe sepsis, but current methods to identify antibiotic resistance still generally rely on bacterial culture. Modern diagnostics promise rapid gene detection, but the apparent diversity of relevant resistance genes in Enterobacteriaceae is a problem. Local surveys and analysis of publicly available data sets suggested that the resistance gene pool is dominated by a relatively small subset of genes, with a very high positive predictive value for phenotype. In this study, 152 Escherichia coli and 115 Klebsiella pneumoniae consecutive isolates with a cefotaxime, ceftriaxone and/or ceftazidime minimum inhibitory concentration (MIC) of ≥2μg/mL were collected from seven major hospitals in Sydney (Australia) in 2008–2009. Nearly all of those with a MIC in excess of European Committee on Antimicrobial Susceptibility Testing (EUCAST) resistance breakpoints contained one or more representatives of only seven gene types capable of explaining this phenotype, and this included 96% of those with a MIC≥2μg/mL to any one of these drugs. Similarly, 97% of associated gentamicin-non-susceptibility (MIC≥8μg/mL) could be explained by three gene types. In a country like Australia, with a background prevalence of resistance to third-generation cephalosporins of 5–10%, this equates to a negative predictive value of >99.5% for non-susceptibility and is therefore suitable for diagnostic application. This is an important proof-of-principle that should be tested in other geographic locations. [Copyright &y& Elsevier]

Abstract: Although cephalosporins are recommended as primary agents, moxifloxacin may be a suitable second-line antibiotic in cardiac surgery, especially if additional Gram-negative coverage is warranted. Cardiopulmonary bypass (CPB) may alter the pharmacokinetics of drugs in numerous ways. Since no such data exist, the aim of this study was to assess the serum concentrations and pharmacokinetics of moxifloxacin in patients undergoing cardiac surgery with CPB. Fourteen coronary artery bypass graft surgery patients received an intravenous infusion of 400mg moxifloxacin as peri-operative antibiotic prophylaxis. At 15 time points throughout a 24-h period, serum samples were obtained to measure moxifloxacin concentrations using high-performance liquid chromatography. In addition, a non-compartmental pharmacokinetic analysis, i.e. area under the concentration–time curve (AUC), volume of distribution at steady state (V SS), drug clearance (CL), elimination half-life (t 1/2) and mean residence time (MRT), was performed in five patients. Apart from a slight transient decrease in moxifloxacin concentration at the onset, CPB did not affect the concentration–time curve. Mean±standard deviation maximum drug concentration (C max) (5.12±1.58μg/mL), AUC (36.5±5.40μgh/mL), V SS (2.03±0.30L/kg), CL (11.2±1.91L/h), t 1/2 (9.47±0.92h) and MRT (12.9±1.52h) were comparable with historical data for healthy volunteers. We conclude that CPB does not alter the pharmacokinetics of moxifloxacin. No dose adjustments, especially with regard to the CPB circuit and its priming volume, are necessary in cardiac surgical patients. [Copyright &y& Elsevier]

Abstract: Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil, is a novel cephalosporin exhibiting bactericidal activity in vitro against Gram-positive organisms, including meticillin-susceptible Staphylococcus aureus (MSSA), meticillin-resistant S. aureus (MRSA), β-haemolytic streptococci, viridans group streptococci (VGS) and Streptococcus pneumoniae, as well as against many common Gram-negative organisms. The objective of this study was to determine the spectrum and potency of ceftaroline against recent (2010) leading pathogens causing complicated skin and soft-tissue infections (cSSTIs) isolated in Europe. A total of 2438 isolates from the Assessing Worldwide Antimicrobial Resistance and Evaluation (AWARE) programme were identified as cSSTI pathogens. Isolates were collected from patients in 52 medical centres in 19 European countries. Reference susceptibility testing for ceftaroline and commonly used antimicrobials was performed by broth microdilution methodologies. Ceftaroline was very active overall against S. aureus (MIC50/90 =0.25/1mg/L) and inhibited 100.0% of isolates at a MIC of ≤2mg/L. Activity against MRSA was documented (MIC50/90 =1/2mg/L) but was lower than that observed against MSSA (MIC50/90 =0.25/0.25mg/L). Ceftaroline was also very active against 460 β-haemolytic streptococci and 93 VGS (MIC90 =0.015mg/L and 0.06mg/L, respectively). Ceftaroline was active against Escherichia coli (MIC50 =0.12mg/L) and Klebsiella pneumoniae (MIC50 =0.06mg/L) not expressing extended-spectrum β-lactamases, with activity similar to ceftriaxone and ceftazidime. In summary, this study documents the potent in vitro activity of ceftaroline when tested against recent pathogens isolated from patients with cSSTI in Europe. [Copyright &y& Elsevier]