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Objectives Despite the introduction of cystic fibrosis transmembrane conductance regulator (CFTR) modulators, Pseudomonas aeruginosa is still a major pathogen in people with cystic fibrosis (pwCF). We determine the activity of cefiderocol and comparators in a collection of 154 P. aeruginosa isolates recovered from pwCF during three multicentre studies performed in 17 Spanish hospitals in 2013, 2017 and 2021. Methods ISO broth microdilution was performed and MICs were interpreted with CLSI and EUCAST criteria. Mutation frequency and WGS were also performed. Results Overall, 21.4% were MDR, 20.8% XDR and 1.3% pandrug-resistant (PDR). Up to 17% of the isolates showed a hypermutator phenotype. Cefiderocol demonstrated excellent activity; only 13 isolates (8.4%) were cefiderocol resistant by EUCAST (none using CLSI). A high proportion of the isolates resistant to ceftolozane/tazobactam (71.4%), meropenem/vaborbactam (70.0%), imipenem/relebactam (68.0%) and ceftazidime/avibactam (55.6%) were susceptible to cefiderocol. Nine out of 13 cefiderocol-resistant isolates were hypermutators (P  < 0.001). Eighty-three STs were detected, with ST98 being the most frequent. Only one isolate belonging to the ST175 high-risk clone carried bla VIM-2. Exclusive mutations affecting genes involved in membrane permeability, AmpC overexpression (L320P-AmpC) and efflux pump up-regulation were found in cefiderocol-resistant isolates (MIC = 4–8 mg/L). Cefiderocol resistance could also be associated with mutations in genes related to iron uptake (tonB -dependent receptors and pyochelin/pyoverdine biosynthesis). Conclusions Our results position cefiderocol as a therapeutic option in pwCF infected with P. aeruginosa resistant to most recent β-lactam/β-lactamase inhibitor combinations. [ABSTRACT FROM AUTHOR]

Objectives To assess the microbiological characteristics of Escherichia coli causing healthcare-associated bacteraemia of urinary origin (HCA-BUO) in Spain (ITUBRAS-2 project), with particular focus on ESBL producers and isolates belonging to ST131 high-risk clone (HiRC). Clinical characteristics and outcomes associated with ST131 infection were investigated. Methods A total of 222 E. coli blood isolates were prospectively collected from patients with HCA-BUO from 12 tertiary-care hospitals in Spain (2017–19). Antimicrobial susceptibility and ESBL/carbapenemase production were determined. ST131 subtyping was performed. A subset of 115 isolates were selected for WGS to determine population structure, resistome and virulome. Clinical charts were reviewed. Results ESBL-producing E. coli prevalence was 30.6% (68/222). ST131 represented 29.7% (66/222) of E. coli isolates and accounted for the majority of ESBL producers (46/68, 67.6%). The C2/H30-Rx subclone accounted for most ST131 isolates (44/66) and was associated with CTX-M-15 (37/44) and OXA-1 enzymes (27/44). Cluster C1-M27 was identified in 4/10 isolates belonging to subclade C1/H30-R1 and associated with CTX-M-27. Additionally, ST131 isolates showed a high content of other acquired resistance genes, and clade C/ST131 isolates carried characteristic QRDR mutations. They were categorized as uropathogenic E. coli and had higher aggregate virulence scores. ST131 infection was associated with more complex patients, prior use of cephalosporins and inadequate empirical treatment but was not associated with worse clinical outcomes. Conclusions ST131 HiRC is the main driver of ESBL-producing E. coli causing HCA-BUO in Spain, mainly associated with the expansion of subclade CTX-M-15-C2/H30-Rx and the emergence of CTX-M-27-C1/H30-R1 (Cluster C1-M27). [ABSTRACT FROM AUTHOR]

Objectives Ceftazidime/avibactam and cefiderocol are two of the latest antibiotics with activity against a wide variety of Gram-negatives, including carbapenem-resistant Enterobacterales. We sought to describe the phenotypic and genotypic characteristics of ceftazidime/avibactam- and cefiderocol-resistant KPC- Klebsiella pneumoniae (KPC- Kp) detected during an outbreak in 2020 in the medical ICU of our hospital. Methods We collected 11 KPC- Kp isolates (6 clinical; 5 surveillance samples) resistant to ceftazidime/avibactam and cefiderocol from four ICU patients (November 2020 to January 2021), without prior exposure to these agents. All patients had a decontamination regimen as part of the standard ICU infection prevention protocol. Additionally, one ceftazidime/avibactam- and cefiderocol-resistant KPC- Kp (June 2019) was retrospectively recovered. Antibiotic susceptibility was determined by broth microdilution. β-Lactamases were characterized and confirmed. WGS was also performed. Results All KPC- Kp isolates (ceftazidime/avibactam MIC  ≥16/4 mg/L; cefiderocol MIC ≥4 mg/L) were KPC + CTX-M-15 producers and belonged to the ST307 high-risk-clone (ST307-HRC). KPC-62 (L168Q) was detected in all isolates involved in the 2020 outbreak, contained in January 2021. KPC-31 (D179Y) was identified in the KPC- Kp from 2019. Cloning experiments demonstrated that both bla KPC-62 and bla KPC-31 were responsible for ceftazidime/avibactam resistance (MIC >16 mg/L) and an increased cefiderocol MIC. Additionally, mutations in OmpA and EnvZ/OmpR porin proteins (in KPC-62- Kp) and in PBP2 (in KPC-31- Kp) were found and may be involved in cefiderocol resistance. Conclusions The emergence of resistance to both ceftazidime/avibactam and cefiderocol in KPC- Kp -HRCs, together with the diversification of novel KPC enzymes displaying different antibiotic resistance phenotypes, is an epidemiological and clinical risk. [ABSTRACT FROM AUTHOR]

Objectives: To detect a potential hidden dissemination of the blaOXA-48 gene among Proteus mirabilis isolates obtained from a single centre.Methods: P. mirabilis from diverse clinical samples presenting an ESBL phenotype or obtained from blood cultured from 2017 to 2019 were evaluated. Bacterial identification was performed using MALDI-TOF MS. MICs were determined using International Organization for Standardization (ISO) standard microdilution and interpreted following EUCAST guidelines. WGS was performed using both short- and long-read technologies and assemblies were done using Unicycler. Resistomes were assessed using the ResFinder database. SNPs were detected using the PATRIC bioinformatics platform. Cloning experiments were performed using the pCRII-TOPO cloning kit.Results: Thirty-one out of 108 (28.7%) isolates were positive for blaOXA-48 and blaCTX-M-15. Twenty-nine out of 31 of the isolates were susceptible to temocillin, piperacillin/tazobactam, ertapenem and meropenem, whereas only 2/31 showed a resistance phenotype against these antibiotics. Both blaOXA-48 and blaCTX-M-15 genes were detected within the same chromosomally integrated new transposon in all isolates. The resistant isolates displayed a single mutation located in the putative promoter upstream of blaOXA-48. Cloning experiments confirmed that the mutation was responsible for the resistance phenotype.Conclusions: The presence of a chromosomal copy of blaOXA-48 did not confer resistance to carbapenems, but a single mutation in the promoter could lead to an increase in resistance. This study shows a hidden circulation of OXA-48-positive, but carbapenem- and piperacillin/tazobactam-susceptible, P. mirabilis isolates that can become resistant to β-lactams after a single mutation. [ABSTRACT FROM AUTHOR]

Background In the late 1990s, as a response to rising antimicrobial resistance (AMR), an independent multinational, interdisciplinary group was formed specifically targeting primary care antibiotic prescribing for community-acquired respiratory tract infections (CA-RTIs). The group comprised senior clinicians from Canada, Israel, Spain, Sweden, UK and USA. The group's objectives were to provide recommendations for antibiotic stewardship in the community because, whilst it was widely accepted that inappropriate antibiotic use was contributing to AMR, it remained difficult to change prescribing behaviour. The group aimed to identify principles underlying appropriate antibiotic prescribing and guideline formulation to reduce morbidity from CA-RTIs, limit therapeutic failure and, importantly, curb AMR emergence. The group published a report in 2002, which has become known as the Consensus Principles. Objectives (i) To consider the relevance of the Consensus Principles in 2022 by reviewing current global approaches to rising AMR. A wide range of factors, such as antibiotic overuse, most recently seen in COVID-19 patients, are still driving rising AMR even though there has been a high-level international response to the AMR threat; and (ii) as an introduction to this Supplement, which reports the findings of analyses of how AMR is being addressed in nine disparate countries (Brazil, India, Kuwait, Mexico, Pakistan, Russia, Saudi Arabia, Türkiye and Vietnam). Understanding how these initiatives are being pursued in different countries helps identify areas where more information is needed. Conclusions Adherence to the Consensus Principles remains as important now as it was in 2002. Achieving appropriate antibiotic prescribing is a vital objective in order that the right patient receives the right antibiotics at the right time to ensure optimal clinical outcomes while at the same time helping to limit further increases in AMR. [ABSTRACT FROM AUTHOR]

Inhaled antibiotics are a common and valuable therapy for patients suffering from chronic lung infection, with this particularly well demonstrated for patients with cystic fibrosis. However, in vitro tests to predict patient response to inhaled antibiotic therapy are currently lacking. There are indications that antimicrobial susceptibility testing (AST) may have a role in guidance of therapy, but which tests would correlate best still needs to be researched in clinical studies or animal models. Applying the principles of European Committee on Antimicrobial Susceptibility Testing methodology, the analysis of relevant and reliable data correlating different AST tests to patients' outcomes may yield clinical breakpoints for susceptibility, but these data are currently unavailable. At present, we believe that it is unlikely that standard determination of minimum inhibitory concentration will prove the best predictor. [ABSTRACT FROM AUTHOR]

Membrane computing is a natural computing procedure inspired in the compartmental structure of living cells. This approach allows mimicking the complex structure of biological processes, and, when applied to transmissible diseases, can simulate a virtual 'epidemic' based on interactions between elements within the computational model according to established conditions. General and focused vaccination strategies for controlling SARS-Cov-2 epidemics have been simulated for 2.3 years from the emergence of the epidemic in a hypothetical town of 10320 inhabitants in a country with mean European demographics where COVID-19 is imported. The age and immunological-response groups of the hosts and their lifestyles were minutely examined. The duration of natural, acquired immunity influenced the results; the shorter the duration, the more endemic the process, resulting in higher mortality, particularly among elderly individuals. During epidemic valleys between waves, the proportion of infected patients belonging to symptomatic groups (mostly elderly) increased in the total population, a population that largely benefits from standard double vaccination, particularly with boosters. There was no clear difference when comparing booster shots provided at 4 or 6 months after standard double-dose vaccination. Vaccines even of moderate efficacy (short-term protection) were effective in decreasing the number of symptomatic cases. Generalized vaccination of the entire population (all ages) added little benefit to overall mortality rates, and this situation also applied for generalized lockdowns. Elderly-only vaccination and lockdowns, even without general interventions directed to reduce population transmission, is sufficient for dramatically reducing mortality. Membrane computing technology simulates the effect of generalized or focused vaccination and lockdown in a town with detailed demographic complexity, experiencing an in silico SARS-Cov-2 epidemic over the course of 2.3 years. [ABSTRACT FROM AUTHOR]

Objectives: To determine the activity of murepavadin in comparison with tobramycin, colistin and aztreonam, against cystic fibrosis (CF) Pseudomonas aeruginosa isolates growing in biofilms. The biofilm-epidemiological cut-off (ECOFF) values that include intrinsic resistance mechanisms present in biofilms were estimated.Methods: Fifty-three CF P. aeruginosa isolates from respiratory samples were tested using the Calgary (closed system) device, while 4 [2 clinical (one smooth, one mucoid) and 2 reference strains] were tested using the BioFlux, a microfluidic open model of biofilm testing. Biofilm was stained with SYTO9® and propidium iodide. The minimal biofilm inhibitory concentration (MBIC) and the minimal biofilm eradication concentration (MBEC) were determined. The MBIC-ECOFF and the MBEC-ECOFF were calculated.Results: Colistin, tobramycin and murepavadin presented similar MBIC50/MBIC90 values (4/32, 8/64 and 2/32, respectively). Murepavadin exhibited the lowest MBEC90 (64 mg/L). Aztreonam MBIC and MBEC values were higher than those of the other antibiotics tested. Tobramycin and murepavadin had the lowest MBEC-ECOFF (64 and 128 mg/L, respectively), while those of aztreonam and colistin exceeded 512 mg/L. Using the BioFlux, for the PAO1, PAO mutS and the smooth clinical strain, a significant difference (P < 0.0125) was observed when comparing the fluorescence of treated and untreated biofilms. For the mucoid strain, only the biofilm treated with aztreonam (MBIC and MBEC) and tobramycin (MBEC) showed differences with respect to the untreated biofilm.Conclusions: Murepavadin demonstrated good activity against P. aeruginosa biofilms both in open and closed systems. The MBIC-ECOFF and the MBEC-ECOFF are proposed as new parameters to estimate the activity of antibiotics on biofilms. [ABSTRACT FROM AUTHOR]

Purpose: to characterize the distribution and mechanisms involved in ceftolozane/tazobactam (C/T) resistance in Pseudomonas aeruginosa isolates recovered from intensive care units (ICUs) in Portugal as part of the STEP surveillance study. Materials and methods: a total of 226 P. aeruginosa isolates were collected from patients with low respiratory tract infections (LRTI) admitted to ICUs between June 2017 and July 2018. Susceptibility to antimicrobials including the recent C/T combination was determined by EUCAST-criteria. Whole genome sequencing (WGS) was performed in a subset of 17 isolates. Results: multidrug resistant (MDR) and extremely drug resistant (XDR) phenotypes accounted for 20.4% and 25.7% of cases, respectively. C/T showed the highest susceptibility rate in both MDR (100%) and XDR (93.1%) isolates, followed by amikacin (97.8% MDR and 79.3% XDR). bla KPC-3 (n  = 2) and bla GES-13 (n  = 1) carbapenemase genes were detected in 3 of the 17 sequenced isolates, but only the GES-13-producing isolate displayed resistance to C/T. Additionally, the C/T-resistant phenotype was also found in two non-carbapenemase producers that carried known ceftolozane/tazobactam resistance-associated mutations in the PBP3 gene. Conclusions: C/T was highly active against MDR/XDR- P. aeruginosa isolates causing LRTI in ICUs. Moreover, beyond carbapenemase-encoding genes, mutations in chromosomal PBP-encoding genes might also be involved in ceftolozane/tazobactam resistance in Portugal. [ABSTRACT FROM AUTHOR]

Objectives: The worldwide emergence of antibiotic resistance calls for effective exploitation of existing antibiotics. Antibiotic combinations with different modes of action can synergize for successful treatment. In the present study, we used microcalorimetry screening to identify synergistic combination treatments against clinical MDR isolates. The synergistic effects were validated in a murine infection model.Methods: The synergy of meropenem combined with colistin, rifampicin or amikacin was tested on 12 isolates (1 Escherichia coli, 5 Klebsiella pneumoniae, 3 Pseudomonas aeruginosa and 3 Acinetobacter baumannii) in an isothermal microcalorimeter measuring metabolic activity. One A. baumannii strain was tested with two individual pairings of antibiotic combinations. The microcalorimetric data were used to predict in vivo efficacy in a murine peritonitis/sepsis model. NMRI mice were inoculated intraperitoneally and after 1 h treated with saline, drug X, drug Y or X+Y. Bacterial load was determined by cfu in peritoneal fluid and blood after 4 h.Results: In vitro, of the 13 combinations tested on the 12 strains, 3 of them exhibited a synergistic reduction in MIC (23% n = 3/13), 5 showed an additive effect (38.5% n = 5/13) and 5 had indifferent or antagonistic effects (38.5% n = 5/13). There was a significant correlation (P = 0.024) between microcalorimetry-screening FIC index values and the log reduction in peritoneal fluid from mice that underwent combination treatment compared with the most effective mono treatment. No such correlation could be found between chequerboard and in vivo results (P = 0.16).Conclusions: These data support microcalorimetic metabolic readout to predict additive or synergistic effects of combination treatment of MDR infections within hours. [ABSTRACT FROM AUTHOR]

Background: Murepavadin, a novel peptidomimetic antibiotic, is being developed as an inhalation therapy for treatment of Pseudomonas aeruginosa respiratory infection in people with cystic fibrosis (CF). It blocks the activity of the LptD protein in P. aeruginosa causing outer membrane alterations.Objectives: To determine the in vitro activity of murepavadin against CF P. aeruginosa isolates and to investigate potential mechanisms of resistance.Methods: MIC values were determined by both broth microdilution and agar dilution and results compared. The effect of artificial sputum and lung surfactant on in vitro activity was also measured. Spontaneous mutation frequency was estimated. Bactericidal activity was investigated using time-kill assays. Resistant mutants were studied by WGS.Results: The murepavadin MIC50 was 0.125 versus 4 mg/L and the MIC90 was 2 versus 32 mg/L by broth microdilution and agar dilution, respectively. Essential agreement was >90% when determining in vitro activity with artificial sputum or lung surfactant. It was bactericidal at a concentration of 32 mg/L against 95.4% of the strains within 1-5 h. Murepavadin MICs were 2-9 two-fold dilutions higher for the mutant derivatives (0.5 to >16 mg/L) than for the parental strains. Second-step mutants were obtained for the PAO mutS reference strain with an 8×MIC increase. WGS showed mutations in genes involved in LPS biosynthesis (lpxL1, lpxL2, bamA2, lptD, lpxT and msbA).Conclusions: Murepavadin characteristics, such as its specific activity against P. aeruginosa, its unique mechanism of action and its strong antimicrobial activity, encourage the further clinical evaluation of this drug. [ABSTRACT FROM AUTHOR]

Objectives: Carbapenemase-producing Enterobacterales (CPE) are increasingly recognized in nosocomial infections, also affecting ICU patients. We aimed to characterize the carbapenemase-producing Serratia marcescens (CPSm) isolates recovered in our hospital in Madrid (Spain) between March 2016 and December 2018.Methods: Overall, 50 isolates from clinical and epidemiological surveillance samples were recovered from 24 patients admitted to the medical ICU and 10 non-ICU-related patients based on their phenotypic resistance. Carbapenemase characterization, antibiotic susceptibility, PFGE clonal relatedness, plasmid characterization, WGS (Illumina-NovaSeq 6000) and phylogenetic analysis were performed.Results: A single isolate was finally considered for each patient, except for Patient 8 that was colonized by two different isolates (n = 35). Isolates were characterized as VIM-1 (n = 29) or OXA-48 producers (n = 6). Up to seven genetic lineages were found by PFGE, with dominance of two clones. Plasmid characterization confirmed that almost all CPSm carried the same ∼60 kb IncL OXA-48- or VIM-1-encoding plasmid, which was related to the globally disseminated IncL-pOXA-48a. WGS allowed plasmid reconstruction with two variants: IncL-pVIM-1 (∼65 kb) and IncL-pOXA-48 (∼62 kb). blaOXA-48-Tn1999 (∼5 kb) was the unique antibiotic resistance gene in pOXA-48, whereas pVIM-1 plasmids (∼8 kb) harboured a class 1 integron containing 5'-blaVIM-1+aacA4+dfrB1+aadA1+catB2+qacEDelta1+sul1-3'.Conclusions: Our results confirm the dissemination of CPSm within our institution in both ICU and non-ICU environments, representing two prevalent CPSm clones, and the same IncL-pOXA-48 plasmid previously described in other Enterobacterales, but containing the blaVIM-1 gene. This also reinforces the relevance of species different from Klebsiella pneumoniae or Escherichia coli in the CPE landscape and circulating lineages and plasmids in local CPE epidemiology. [ABSTRACT FROM AUTHOR]

The capacity of Candida spp. to form biofilms allows them to attach either to living or inert surfaces, promoting their persistence in hospital environments. In a previous study, we reported strain-to-strain variations in Candida spp. biofilm development, suggesting that some genotypes may be greater biofilm formers than others. In this study, we hypothesize that isolates pertaining to clusters may be found more frequently in the environment due to their ability to form biofilms compared to singleton genotypes. Two hundred and thirty-nine Candida spp. isolates (78 clusters) from candidemia patients admitted to 16 hospitals located in different cities and countries—and the same number of singleton genotypes used as controls—were tested in terms of biofilm formation using the crystal violet and the XTT reduction assays. Candida albicans clusters showed higher biofilm formation in comparison to singleton genotypes (P  < .01). The biofilms formed by intra-hospital C. albicans clusters showed higher metabolic activity (P  < .05). Furthermore, marked variability was found among species and type of cluster. We observed that the higher the number of isolates, the higher the variability of biofilm production by isolates within the cluster, suggesting that the production of biofilm by isolates of the same genotype is quite diverse and does not depend on the type of cluster studied. In conclusion, candidemia Candida spp. clusters—particularly in the case of C. albicans —show significantly more biomass production and metabolic activity than singleton genotypes. [ABSTRACT FROM AUTHOR]

Objectives: To describe the incidence and microbiological features of carbapenemase-producing Enterobacteriaceae (CPE) from colonized patients in a Spanish university hospital during a cluster-randomized study [the Resistance of Gram-Negative Organisms: Studying Intervention Strategies (R-GNOSIS) project] on isolation strategies for faecal ESBL carriers.Methods: From March 2014 to March 2016, 15 556 rectal swabs from 8209 patients admitted in two surgical wards and two medical wards were collected and seeded on ESBL and CPE chromogenic agars. Carbapenemase characterization (PCR and sequencing) was performed, and antibiotic susceptibility (MIC), clonality (PFGE and MLST) and diversity (Simpson diversity index estimation) were determined.Results: One hundred and ninety-eight CPE isolates, mainly Klebsiella pneumoniae (53.5%) and Escherichia coli (19.2%), were identified in 162 patients (2%). Prevalence of CPE carriage remained unchanged over time. Overall, amikacin (9.6%), tigecycline (9.6%) and colistin (0.5%) showed low non-susceptibility. The most frequent carbapenemase was OXA-48 (64.1%), followed by VIM-1 (26.8%), NDM-1 (5.3%) and KPC-3 (3.5%), and these were co-produced with ESBLs in 43.9%. OXA-48 plus CTX-M-15 was the most frequent association. Two major K. pneumoniae clones were identified (OXA-48-CTX-M-15-ST11 and VIM-1-SHV-12-ST54) with considerable genetic diversity among the remaining isolates, including OXA-48-E. coli. Species diversity tended to decrease from 0.75 in the first 6 months of the study to 0.43 in the final months. The emergence of new clones (i.e. OXA-48-Kluyvera spp. and NDM-1-K. pneumoniae ST437 and ST101) and displacement of other particular clones were also demonstrated.Conclusions: We describe a polyclonal and changeable CPE population over time. Coexistence of worldwide disseminated clones, such as ST11-OXA-48- K. pneumoniae, with unrelated and emerging OXA-48-E. coli clones, depicts a disturbing CPE epidemiology in our institution. [ABSTRACT FROM AUTHOR]

We studied the ability of five echinocandin-susceptible C. glabrata isolates to acquire in vitro resistance to anidulafungin and micafungin. All isolates became phenotypically resistant after 2–4 days of exposure to low and constant micafungin concentrations (P <.05). Mutations in the HS1 region of the FKS2 gene were found in all isolates. The acquisition of resistance was not related to the previous use of antifungal treatment in the patients or the presence of mutations at MSH2 gene. We found differences (P <.0001) in the median survival of Galleria mellonella larvae infected with FKS2 mutant isolates (5 days) and wild-type isolates (3 days). [ABSTRACT FROM AUTHOR]

Objectives: To compare results of amoxicillin/clavulanate susceptibility testing using CLSI and EUCAST methodologies and to evaluate their impact on outcome in patients with bacteraemia caused by Enterobacteriaceae.Patients and methods: A prospective observational cohort study was conducted in 13 Spanish hospitals. Patients with bacteraemia due to Enterobacteriaceae who received empirical intravenous amoxicillin/clavulanate treatment for at least 48 h were included. MICs were determined following CLSI and EUCAST recommendations. Outcome variables were: failure at the end of treatment with amoxicillin/clavulanate (FEAMC); failure at day 21; and 30 day mortality. Classification and regression tree (CART) analysis and logistic regression were performed.Results: Overall, 264 episodes were included; the urinary tract was the most common source (64.7%) and Escherichia coli the most frequent pathogen (76.5%). Fifty-two isolates (19.7%) showed resistance according to CLSI and 141 (53.4%) according to EUCAST. The kappa index for the concordance between the results of both committees was only 0.24. EUCAST-derived, but not CLSI-derived, MICs were associated with failure when considered as continuous variables. CART analysis suggested a 'resistance' breakpoint of > 8/4 mg/L for CLSI-derived MICs; it predicted FEAMC in adjusted analysis (OR = 1.96; 95% CI: 0.98-3.90). Isolates with EUCAST-derived MICs >16/2 mg/L independently predicted FEAMC (OR = 2.10; 95% CI: 1.05-4.21) and failure at day 21 (OR= 3.01; 95% CI: 0.93-9.67). MICs >32/2 mg/L were only predictive of failure among patients with bacteraemia from urinary or biliary tract sources.Conclusions: CLSI and EUCAST methodologies showed low agreement for determining the MIC of amoxicillin/clavulanate. EUCAST-derived MICs seemed more predictive of failure than CLSI-derived ones. EUCAST-derived MICs >16/2 mg/L were independently associated with therapeutic failure. [ABSTRACT FROM AUTHOR]

Objectives: β-Lactams are commonly used for nosocomial infections and resistance to these agents among Gram-negative bacteria is increasing rapidly. Optimized dosing is expected to reduce the likelihood of resistance development during antimicrobial therapy, but the target for clinical dose adjustment is not well established. We examined the likelihood that various dosing exposures would suppress resistance development in an in vitro hollow-fibre infection model.Methods: Two strains of Klebsiella pneumoniae and two strains of Pseudomonas aeruginosa (baseline inocula of ∼10 8  cfu/mL) were examined. Various dosing exposures of cefepime, ceftazidime and meropenem were simulated in the hollow-fibre infection model. Serial samples were obtained to ascertain the pharmacokinetic simulations and viable bacterial burden for up to 120 h. Drug concentrations were determined by a validated LC-MS/MS assay and the simulated exposures were expressed as C min /MIC ratios. Resistance development was detected by quantitative culture on drug-supplemented media plates (at 3× the corresponding baseline MIC). The C min /MIC breakpoint threshold to prevent bacterial regrowth was identified by classification and regression tree (CART) analysis.Results: For all strains, the bacterial burden declined initially with the simulated exposures, but regrowth was observed in 9 out of 31 experiments. CART analysis revealed that a C min /MIC ratio ≥3.8 was significantly associated with regrowth prevention (100% versus 44%, P  = 0.001).Conclusions: The development of β-lactam resistance during therapy could be suppressed by an optimized dosing exposure. Validation of the proposed target in a well-designed clinical study is warranted. [ABSTRACT FROM AUTHOR]

Objectives: To compare the concordance of ceftaroline MIC values by reference broth microdilution (BMD) and Etest (bioMérieux, France) for MSSA and MRSA isolates obtained from PREMIUM (D372SL00001), a European multicentre study.Methods: Ceftaroline MICs were determined by reference BMD and by Etest for 1242 MSSA and MRSA isolates collected between February and May 2012 from adult patients with community-acquired pneumonia or complicated skin and soft tissue infections; tests were performed across six European laboratories. Selected isolates with ceftaroline resistance in broth (MIC >1 mg/L) were retested in three central laboratories to confirm their behaviour.Results: Overall concordance between BMD and Etest was good, with >97% essential agreement and >95% categorical agreement. Nevertheless, 12 of the 26 MRSA isolates found resistant by BMD scored as susceptible by Etest, with MICs ≤1 mg/L, thus counting as very major errors, whereas only 5 of 380 MRSA isolates found ceftaroline susceptible in BMD were miscategorized as resistant by Etest. Twenty-one of the 26 isolates with MICs of 2 mg/L by BMD were then retested twice by each of three central laboratories: BMD MICs of 2 mg/L were consistently found for 19 of the 21 isolates. Among 147 Etest results for these 21 isolates (original plus six repeats per isolate) 112 were >1 mg/L.Conclusions: BMD and Etest have good overall agreement for ceftaroline against Staphylococcus aureus; nevertheless, reliable Etest-based discrimination of the minority of ceftaroline-resistant (MIC 2 mg/L) MRSA is extremely challenging, requiring careful reading of strips, ideally with duplicate testing. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the population structure of Enterococcus faecium causing bloodstream infections (BSIs) in a tertiary Spanish hospital with low glycopeptide resistance, and to enhance our knowledge of the dynamics of emergence and spread of high-risk clonal complexes.Methods: All available E. faecium causing BSIs (n = 413) in our hospital (January 1995-May 2015) were analysed for antibiotic susceptibility (CLSI), putative virulence traits (PCR, esp, hylEfm) and clonal relationship (SmaI-PFGE, MLST evaluated by goeBURST and BAPS).Results: The increased incidence of BSIs caused by enterococci [2.3‰ of attended patients (inpatients and outpatients) in 1996 to 3.0‰ in 2014] significantly correlated with the increase in BSIs caused by E. faecium (0.33‰ of attended patients in 1996 to 1.3‰ in 2014). The BSIs Enterococcus faecalis:E. faecium ratio changed from 5:1 in 1996 to 1:1 in 2014. During the last decade an increase in E. faecium BSIs episodes in cancer patients (10.9% in 1995-2005 and 37.1% in 2006-15) was detected. Ampicillin-susceptible E. faecium (ASEfm; different STs/BAPS) and ampicillin-resistant E. faecium (AREfm; ST18/ST17-BAPS 3.3a) isolates were recovered throughout the study. Successive waves of BAPS 2.1a-AREfm (ST117, ST203 and ST80) partially replaced ASEfm and ST18-AREfm since 2006.Conclusions: Different AREfm clones (belonging to BAPS 2.1a and BAPS 3.3a) consistently isolated during the last decade from BSIs might be explained by a continuous and dense colonization (favouring both invasion and cross-transmission) of hospitalized patients. High-density colonization by these clones is probably enhanced in elderly patients by heavy and prolonged antibiotic exposure, particularly in oncological patients. [ABSTRACT FROM AUTHOR]

Objectives: The objective of this study was to assess the prevalence and molecular epidemiology of ESBL-producing Escherichia coli causing healthcare-associated (HCA) and community-associated (CA) bacteraemia of urinary origin (BUO) in Spain.Methods: An observational cohort study was conducted at eight hospitals from different Spanish geographical areas (2010-11). BUO episodes (n = 425) were classified as HCA (n = 215) and CA (n = 210), and one blood isolate per episode was collected. Susceptibility testing was performed, ESBLs were screened by double-disc diffusion test and ESBL and OXA-1 genes were characterized (PCR and sequencing). Population structure (phylogenetic groups, XbaI-PFGE and MLST) and ST131 subtyping (PCR) were determined. Virulence genes were detected by PCR and virulence score, profiles and extraintestinal pathogenic E. coli (ExPEC) status calculated.Results: ESBL-producing E. coli prevalence was 9.2% (39/425). ESBL-producing E. coli episodes were significantly associated with HCA-BUO episodes [14% (30/215) versus 4.3% (9/210); P = 0.001]. The highest non-susceptibility proportions corresponded to ciprofloxacin (97.4%), amoxicillin/clavulanate (74.4%), co-trimoxazole (69.2%) and tobramycin (61.5%). Of the 39 ESBL-producing E. coli isolates, 34 produced CTX-M enzymes (21 CTX-M-15, 11 CTX-M-14 and 2 CTX-M-1). Fifteen STs were identified, the B2-ST131 clone being the most prevalent (54%; 21/39). All ST131 isolates were ExPEC and had the highest virulence scores, but they showed less diversity in virulence profiles than other STs. The H30Rx subclone accounted for most ST131 isolates (20/21), co-produced CTX-M-15 (20/20) and OXA-1 (19/20) enzymes and was associated with HCA episodes (16/20).Conclusions: The CTX-M-15-ST131-H30Rx subclone is a relevant MDR pathogen causing BUO, mainly HCA episodes. The dominance of this subclone with comparatively less diversity of virulence profiles reflects the spread of a successful and MDR ESBL ST131 lineage in Spain. [ABSTRACT FROM AUTHOR]

The activities of nalidixic acid, ciprofloxacin, norfloxacin, ofloxacin, pefloxacin, flerofloxacin, sparfloxacin, grepafloxacin, gatifloxacin, moxifloxacin, trovafloxacin, levofloxacin and clinafloxacin against a panel of Haemophilus influenzae strains were assessed by three susceptibility testing methods: Etest, agar dilution and the reference broth microdilution method using Haemophilus test medium (HTM) in all cases. The panel included 62 clinical and two reference H. influenzae strains; 32 had decreased susceptibility to ciprofloxacin (MIC > or = 0.12 mg/L) and 30 were susceptible to this antibiotic (MIC < or = 0.06 mg/L). Both Etest and HTM agar dilution results (r = 0.96; 86.61% and 82.1% of MICs within + one log(2), respectively) correlated well with the reference microdilution method. The MIC(90) of ciprofloxacin was 4.0 mg/L (range 0.007-32.0 mg/L). Trovafloxacin activity was similar to that of ciprofloxacin but sparfloxacin, grepafloxacin, ofloxacin, pefloxacin and flerofloxacin activities were higher (with MIC values one log(2) dilution lower than ciprofloxacin). The least active were norfloxacin (MIC(90) 16 mg/L) and nalidixic acid (MIC(90) 128 mg/L). Levofloxacin and moxifloxacin were more active than ciprofloxacin (MIC(90) 2 mg/L); clinafloxacin and gatifloxacin were the most active with an MIC(90) of 0.25 mg/L. Cross-susceptibility among all quinolones was observed (r > 0.9). Resistance to ciprofloxacin was associated with a similar magnitude of activity loss to other new and old quinolones. Ciprofloxacin MIC determination should be sufficient to detect the decreased susceptibility to the whole group of quinolones. [ABSTRACT FROM AUTHOR]

Objective: Our objective was to evaluate the impact of low versus borderline MIC of piperacillin/tazobactam on the clinical outcomes of patients with bacteraemia caused by Enterobacteriaceae who were treated with that antimicrobial. Patients and methods: A prospective observational multicentre cohort study was conducted in 13 Spanish university hospitals. Patients >17 years old with bacteraemia due to Enterobacteriaceae who received empirical piperacillin/tazobactam treatment for at least 48 h were included. Outcome variables were clinical response at day 21, clinical response at end of treatment with piperacillin/tazobactam and all-cause 30 day mortality. Univariate and multivariate logistic regression analyses were performed. Results: Overall, 275 patients were included in the analysis; 248 (90.2%) in the low MIC group (≤4 mg/L) and 27 (9.8%) in the borderline MIC group (8-16 mg/L). The biliary tract was the most common source of infection (48.4%) and Escherichia coli was the most frequent pathogen (63.3%). Crude 30 day mortality rates were 10.5% and 11.1% for the low MIC group and the borderline MIC group, respectively (relative risk = 1.06, 95% CI = 0.34-3.27, P = 1). Multivariate analysis of failure at day 21 and at end of treatment with piperacillin/tazobactam and 30 day mortality showed no trend towards increased clinical failure or mortality with borderline MICs (OR = 0.96, 95% CI = 0.18-4.88, P = 0.96; OR = 0.47, 95% CI = 0.10-2.26, P = 0.35; OR = 1.48, 95% CI = 0.33-6.68, P = 0.6). Conclusions: We did not find that higher piperacillin/tazobactam MICwithin the susceptible or intermediate susceptibility range had a significant influence on the outcome for patients with bacteraemia due to Enterobacteriaceae. [ABSTRACT FROM AUTHOR]

Objectives: The objective of this study was to describe the prevalence and microbiological characteristics of carbapenemase-producing Enterobacteriaceae (CPE) colonizing patients in long-term care hospitals (LTCHs) in Madrid, Spain. Methods: Three LTCHs were included in a single-day point-prevalence survey (September 2013). Rectal swabs, collected from all hospitalized patients (137 in LTCH-A, 121 in LTCH-B and 83 in LTCH-C), were plated onto chromogenic media. Population structure (PFGE and MLST), genes encoding carbapenemases and ESBLs and plasmids carrying carbapenemase genes were characterized. Results The prevalence of CPE carriers was 4.1% (14/341) [2.9% (4/137), LTCH-A; 4.1% (5/121), LTCH-B; and 6.0% (5/83), LTCH-C]. OXA-48 was the most prevalent carbapenemase (nine Klebsiella pneumoniae, two Escherichia coli, one Enterobacter cloacae and one Citrobacter braakii) followed by VIM-1 (one K. pneumoniae and one Raoultella ornithinolytica). One patient (LTCH-C) was co-colonized with OXA-48-producing K. pneumoniae and E. coli. K. pneumoniae and E. coli isolates also coproduced CTX-M-15 (n=11) or CTX-M-9 (n=1) enzymes. K. pneumoniae clustered into six PFGE types corresponding to ST11 (n=1), ST15 (n=6), ST307 (n=1) and ST405 (n=2). E. coli from LTCH-A and LTCH-C exhibited two different PFGE types associated with ST68. OXA-48 and VIM-1 enzymes were found in different clones in LTCH-A and LTCH-C. However, OXA-48 was the only carbapenemase detected in LTCH-B, mainly associated with K. pneumoniae ST15. KPC, IMP and NDM enzymes were not detected. blaOXA-48 was located on an ~60 kb plasmid with a pOXA-48a-IncL/M backbone . Conclusions: We describe the first point-prevalence study of CPE faecal carriers in LTCHs in Spain. OXA-48, the most prevalent carbapenemase, showed a complex dissemination pattern with clonal and polyclonal bacterial populations. [ABSTRACT FROM AUTHOR]

The ability to colonize patients successfully may be essential for the emergence and spread of resistant nosocomial strains. We determined the presence of Esp, a surface protein involved in colonization ability in Enterococcus faecalis, in 96 Enterococcus faecium isolates from hospitalized patients (77 PFGE clones), 33 faecal isolates from healthy volunteers (32 clones) and 20 environmental isolates (20 clones). Esp was found significantly more often in E. faecium isolated from hospitalized patients than in isolates from the community setting (26% versus 6%, P < 0.01) and was significantly more common among ampicillin-resistant than among ampicillin-susceptible strains (37% versus 4%, P < 0.001), regardless of the isolation site. The frequency of the esp gene in the hospital clearly correlates with antibiotic-resistant E. faecium clones. This observation indicates that antibiotic-resistant variants may frequently arise under antibiotic selective pressure among esp-positive clones reaching ecological abundance in the nosocomial habitat. [ABSTRACT FROM AUTHOR]

Background: Carbapenemases are a major concern for the treatment of infectious diseases caused by Gram-negative bacteria. Although plasmids are responsible for the spread of resistance genes among these pathogens, there is limited information on the nature of the mobile genetic elements carrying carbapenemases in Pseudomonas aeruginosa.Methods: We combined data from two different next-generation sequencing platforms, Illumina HiSeq2000 and PacBio RSII, to obtain the complete nucleotide sequences of two blaVIM-1-carrying plasmids (pAMBL1 and pAMBL2) isolated from P. aeruginosa clinical isolates.Results: Plasmid pAMBL1 has 26 440 bp and carries a RepA_C family replication protein. pAMBL1 is similar to plasmids pNOR-2000 and pKLC102 from P. aeruginosa and pAX22 from Achromobacter xylosoxidans, which also carry VIM-type carbapenemases. pAMBL2 is a 24 133 bp plasmid with a replication protein that belongs to the Rep_3 family. It shows a high degree of homology with a fragment of the blaVIM-1-bearing plasmid pPC9 from Pseudomonas putida. Plasmid pAMBL2 carries three copies of the blaVIM-1 cassette in an In70 class 1 integron conferring, unlike pAMBL1, high-level resistance to carbapenems.Conclusions: We present two new plasmids coding for VIM-1 carbapenemase from P. aeruginosa and report that the presence of three copies of blaVIM-1 in pAMBL2 produces high-level resistance to carbapenems. [ABSTRACT FROM AUTHOR]

In the face of increasing antimicrobial resistance and the paucity of new antimicrobial agents it has become clear that new antimicrobial strategies are urgently needed. One of these is to revisit old antibiotics to ensure that they are used correctly and to their full potential, as well as to determine whether one or several of them can help alleviate the pressure on more recent agents. Strategies are urgently needed to 're-develop' these drugs using modern standards, integrating new knowledge into regulatory frameworks and communicating the knowledge fromthe research bench to the bedside.Without a systematic approach to re-developing these old drugs and rigorously testing them according to today's standards, there is a significant risk of doing harm to patients and further increasing multidrug resistance. This paper describes factors to be considered and outlines steps and actions needed to re-develop old antibiotics so that they can be used effectively for the treatment of infections. [ABSTRACT FROM AUTHOR]

Objectives: There are different methodological recommendations for in vitro testing of the co-amoxiclav combination. Performance of co-amoxiclav MIC testing for Escherichia coli by the standard ISO microdilution method (ISO 20776-1) was compared using EUCAST (fixed 2 mg/L clavulanate concentration) and CLSI (2:1 ratio) interpretive criteria. Methods: MICs were determined by broth microdilution using a 2:1 ratio and fixed clavulanate concentrations (2 and 4 mg/L) for 160 clinical E. coli isolates with characterized resistance mechanisms. Essential agreements, categorical agreements and relative errors were determined. Results: For all isolates, essential agreement between microdilution using 2 mg/L clavulanate and a 2:1 ratiowas 25.6%. For ESBL-producing isolates, considering EUCAST breakpoints, 55% of isolates tested with 2 mg/L clavulanate were classified as resistant; conversely, 95% of isolates tested with 4 mg/L clavulanate were susceptible. When using CLSI breakpoints and a 2:1 ratio, 90% of isolates were susceptible and 10% were intermediate. Conclusions: Variation in the clavulanate concentration gave different susceptibility testing results, particularly among ESBL-producing E. coli isolates. The in vitro concentration of clavulanate that better correlates with clinical outcome is still under debate and should be established. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the performance of the eazyplex® SuperBug CRE system, a loop-mediated isothermal amplification (LAMP)-based system, for confirming the presence of carbapenemases in addition to CTX-M-type ESBLs in previously genotypically and/or phenotypically characterized clinical Enterobacteriaceae isolates recovered in two centres in Spain. Methods: A collection of 94 carbapenemase-producing strains previously characterized by conventional PCR and sequencing and a total of 45 prospectively collected isolates with phenotypes compatible with the presence of a carbapenemase were tested with the eazyplex® SuperBug CRE system. In both cases, the presence of an ESBL was also assessed. Results were evaluated to establish the accuracy of this rapid LAMP-based system as well as to determine the concordance between all approaches. Results: The eazyplex® SuperBug CRE system correctly detected bla carbapenemase genes with or without blaCTX-M genes in 100% of the molecularly characterized strains. Absolute concordance (100%) was also observed in the case of isolates with phenotypes compatible with the presence of a carbapenemase with or without an ESBL inferred by susceptibility patterns and phenotypic inhibitory profiles. Determinations performed with the eazyplex® SuperBug CRE system took 15 min. Conclusions: The eazyplex® SuperBug CRE system proved to be a powerful tool for the detection of different carbapenemases as well as CTX-M-type ESBLs in Enterobacteriaceae with a rapid resolution time. The test has the high-performance parameters attributable to the sensitivity and specificity already demonstrated by LAMP-based assays. These results assure the usefulness of this test for routine rapid confirmation of carbapenemase-producing Enterobacteriaceae. [ABSTRACT FROM AUTHOR]

Objectives To analyse the ongoing epidemiology of KPC-producing Enterobacteriaceae after a non-ST258 KPC-3-producing Klebsiella pneumoniae outbreak in a university hospital in Madrid, Spain. Methods Enterobacterial isolates (one per patient based on bacterial identification and typing patterns) with carbapenem MICs higher than the EUCAST epidemiological cut-off values, a positive modified Hodge test and carbapenem/boronic acid combination disc test results were studied (16 March 2010 to 31 January 2012) and compared with KPC-producing isolates previously described in our institution (September 2009 to February 2010). The bacterial population structure (PFGE and multilocus sequence typing), carbapenemase genes and KPC plasmids were studied. Patients' clinical records were reviewed. Results Twenty-four KPC-producing Enterobacteriaceae (20 K. pneumoniae, 2 Escherichia coli and 2 Enterobacter cloacae) from 23 patients (13 males, median age 72 years) were studied. Most KPC-producer strains were considered as colonizers. Six K. pneumoniae clones (ST11, ST20, ST384, ST454, ST659 and ST971), two E. coli clones (ST224 and ST357) and one E. cloacae clone were identified. blaKPC-3 was located on IncFIIK plasmids of ∼100 kb (E. coli ST357 and K. pneumoniae ST384, ST454, ST659 and ST971 clones) and on IncN plasmids of ∼40 kb (K. pneumoniae ST11 clone). Non-typeable plasmids of ∼20 kb containing blaKPC-2 were detected in scarcely represented clones (K. pneumoniae ST20, E. coli ST224 and E. cloacae). Conclusions During the 2 year period following the emergence of non-ST258 KPC-3-producing K. pneumoniae isolates in our institution, the blaKPC-3 and blaKPC-2 genes efficiently penetrated other Enterobacteriaceae lineages. Non-ST258 K. pneumoniae isolates were mostly responsible for the dissemination of KPC enzymes, producing a complex epidemiological picture. [ABSTRACT FROM PUBLISHER]

Background The H1N1 influenza pandemic strain has been associated with a poor prognosis in hospitalized patients. The present report evaluates the factors influencing prognosis. Methods A total of 813 patients hospitalized with H1N1 influenza in 36 hospitals (nationwide) in Spain were analysed. Detailed histories of variables preceding hospital admission were obtained by interview, validating data on medications and vaccine with their attending physicians. Data on treatment and complications during hospital stay were recorded. As definition of poor outcome, the endpoints of death and admission to intensive care were combined; and as a further outcome, length of stay was used. Results The mean age was 38.5 years (SD 22.8 years). There were 10 deaths and 79 admissions to intensive care (combined, 88). The use of neuraminidase inhibitors was reported by 495 patients (60.9%). The variables significantly associated with a poor outcome were diabetes (OR = 2.21, 95% CI = 1.21–4.02), corticosteroid therapy (OR = 3.37, 95% CI = 1.39–8.20) and use of histamine-2 receptor antagonists (OR = 2.68, 95% CI = 1.14–6.36), while the use of neuraminidase inhibitors (OR = 0.57, 95% CI = 0.34–0.94) was protective. Neuraminidase inhibitors within the first 2 days after the influenza onset reduced hospital stay by a mean of 1.9 days (95% CI = 4.7–6.6). Conclusions The use of neuraminidase inhibitors decreases the length of hospital stay and admission to intensive care and/or death. [ABSTRACT FROM PUBLISHER]

Within a susceptible wild-type population, a small fraction of cells, even <10−9, is not affected when challenged by an antimicrobial agent. This subpopulation has mutations that impede antimicrobial action, allowing their selection during clinical treatment. Emergence of resistance occurs in the frame of a selective compartment termed a mutant selection window (MSW). The lower margin corresponds to the minimum inhibitory concentration of the susceptible cells, whereas the upper boundary, named the mutant prevention concentration (MPC), restricts the growth of the entire population, including that of the resistant mutants. By combining pharmacokinetic/pharmacodynamic concepts and an MPC strategy, the selection of resistant mutants can be limited. Early treatment avoiding an increase of the inoculum size as well as a regimen restricting the time within the MSW can reduce the probability of emergence of the resistant mutants. Physiological and, possibly, genetic adaptation in biofilms and a high proportion of mutator clones that may arise during chronic infections influence the emergence of resistant mutants. Moreover, a resistant population can emerge in a specific selective compartment after acquiring a resistance trait by horizontal gene transfer, but this may also be avoided to some extent when the MPC is reached. Known linkage between antimicrobial use and resistance should encourage actions for the design of antimicrobial treatment regimens that minimize the emergence of resistance. Emergence of a resistant bacterial subpopulation within a susceptible wild-type population can be restricted with a regimen using an antibiotic dose that is sufficiently high to inhibit both susceptible and resistant bacteria [ABSTRACT FROM AUTHOR]

Objectives To investigate the mechanisms of carbapenem resistance in the 175 Pseudomonas aeruginosa isolates (39%; 175/448) showing non-susceptibility (European Committee on Antimicrobial Susceptibility Testing breakpoints) to imipenem (35%), meropenem (33%) and/or doripenem (33%) recovered in 2008–09 from 16 Spanish hospitals during the Comparative Activity of Carbapenem Testing (COMPACT) surveillance study. Methods MICs (Etest), clonal relatedness (PFGE) and metallo-β-lactamase (MBL) production (Etest-MBL, PCR and sequencing) were determined. Mutation-driven resistance was studied in 60 non-MBL producers according to the doripenem MICs (15 isolates from each of four MIC groups: ≤1, 2–4, 8–16 and ≥32 mg/L). The expression of ampC, mexB, mexY, mexD and mexF was determined by real-time reverse transcription–PCR and the presence of mutations in oprD by PCR and sequencing. Isogenic mutants expressing combinations of mutation-driven carbapenem resistance were constructed. Results Twelve (6.9%) isolates were MBL (VIM-20, VIM-2 or VIM-13) producers and all showed high-level resistance (MIC 32 mg/L) to all three carbapenems. Regarding mutation-driven resistance, all but 1 of the 60 isolates were non-susceptible (MIC >32 mg/L) to imipenem, linked to oprD inactivation. In addition, 50% of the isolates overexpressed ampC, 33% mexY, 32% mexB and 15% mexF, while none overexpressed mexD. Increasing prevalence of ampC overexpression correlated with increasing doripenem MICs (≤1, 13%; 2–4, 53%; 8–16, 60%; and ≥32, 73%) while overexpression of efflux pumps correlated only with moderate resistance. Doripenem showed slightly higher activity than meropenem against isolates overexpressing ampC, especially mexB or mexY. The analysis of a collection of isogenic laboratory mutants supported this finding. Conclusions Although the prevalence of MBL producers is increasing, mutation-driven resistance is still more frequent in Spain. Imipenem resistance was driven by OprD inactivation, while additional AmpC and particularly efflux pump hyperproduction had a lower impact on the activity of doripenem compared with meropenem. [ABSTRACT FROM PUBLISHER]

Background: KPC carbapenemase-producing Klebsiella pneumoniae isolates have been increasingly detected in Europe. We report the first KPC-producing isolates characterized in Madrid, Spain. [ABSTRACT FROM PUBLISHER]

Nosocomial infections caused by enterococci present a challenge for clinicians because treatment options are often limited due to the widespread occurrence of strains resistant to multiple antibiotics, including vancomycin. Daptomycin is a first-in-class cyclic lipopeptide that has proven efficacy for the treatment of Gram-positive infections. Although methicillin-resistant Staphylococcus aureus has been the most prominent target in the clinical development of daptomycin, this agent has demonstrated potent bactericidal activity in enterococcal infection models and has been used for the treatment of enterococcal infections in humans. In recent years, large-scale susceptibility studies have shown that daptomycin is active against >98% of enterococci tested, irrespective of their susceptibility to other antibacterial agents. This lack of cross-resistance reflects the fact that daptomycin has a mode of action distinct from those of other antibiotics, including glycopeptides. While there are limited data available from randomized controlled trials, extensive clinical experience with daptomycin in enterococcal infections (including bacteraemia, endocarditis, skin and soft tissue infections, bone and joint infections and urinary tract infections) has been reported. This growing body of evidence provides useful insights regarding the efficacy of daptomycin against enterococci in clinical settings. [ABSTRACT FROM PUBLISHER]

Objectives: Erythromycin resistance in Streptococcus pneumoniae is still increasing worldwide. All 78 erythromycin-resistant S. pneumoniae isolates collected from blood cultures in our hospital (2000–07) were studied and the population structure was analysed by using different mathematical diversity indexes. [ABSTRACT FROM PUBLISHER]

The pattern of susceptibility to a range of antimicrobials was tested for 1485 isolates of Streptococcus pyogenes and 1547 isolates of Staphylococcus aureus included in the international PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) surveillance study (1999–2000). Overall, almost 10% of S. pyogenes isolates were erythromycin A resistant. There was a wide heterogeneity of resistance, with high levels of macrolide resistance in Poland (42%), Hong Kong (28%), Italy (25%), Portugal (24%) and Spain (21%), and no macrolide resistance in Indonesia, Austria, Belgium, the Netherlands or the UK. Using NCCLS tentative breakpoints, 97.6% of isolates were susceptible to telithromycin, with MIC90 ≤ 0.015 mg/L in most regions. Resistance among S. pyogenes to the β-lactams (MIC90 ≤ 0.12 mg/L for all except cefaclor) and fluoroquinolones was not detected. Macrolide resistance was present among the S. aureus isolates, and as with S. pyogenes, there was a wide heterogeneity of resistance, with lower rates in Australia, Indonesia, Hungary, Austria, Germany, the Netherlands, Portugal, Sweden and Switzerland. Methicillin-resistant isolates were resistant to the β-lactams and the macrolides. Resistance to telithromycin was detected in methicillin-resistant isolates in Latin and North America, Asia and Europe. Telithromycin resistance was non-existent or low (MIC90 range 0.06–0.25 mg/L) in Australia, Indonesia, Hungary, Austria, Germany, the Netherlands, Portugal, Sweden and Switzerland. Regardless of methicillin susceptibility, resistance to linezolid, teicoplanin or vancomycin was not apparent globally. [ABSTRACT FROM PUBLISHER]

Bacterial resistance to antimicrobial agents is an ever-increasing problem. The in-vitro activity of sparfloxacin compared with that of currently available antimicrobial agents against pathogens implicated in respiratory tract infections is reviewed. Sparfloxacin is a fluoroquinolone active against both penicillin-susceptible and -resistant strains of Streptococcus pneumoniae. It is also active against many other respiratory tract pathogens and may be a suitable alternative for empirical therapy of community-acquired respiratory tract infections. [ABSTRACT FROM PUBLISHER]

Ciprofloxacin has been a major advance in the treatment of chronic respiratory infections. Three patients with cystic fibrosis and colonized by 5 nontypeable Haemophilus influenzae strains exhibiting low- (MIC, 2 µg/mL) and high-level ciprofloxacin resistance (MICs, 16-32 µg/mL) are described. The patients had received several courses of ciprofloxacin. These MICs represent a decrease in ciprofloxacin susceptibility of 200-3200 times. Molecular epidemiologic methods demonstrated that 2 patients were chronically colonized by their own ciprofloxacin-resistant strains for ⩾ 15-17 months. Three strains showed simultaneous resistance to ampicillin and chloramphenicol by enzyme inactivation, and 2 had ampicillin resistance without β-lactamase activity. These data suggest that the emergence and long-term persistence of ciprofloxacin-resistant H. infiuenzae in patients with cystic fibrosis can be a consequence of antibiotic treatment. [ABSTRACT FROM PUBLISHER]

A response by Rafael Cantón and colleagues to a letter to the editor about their article "A Potential Role for Daptomycin in Enterococcal Infections: What is the Evidence?" in the 2010 issue is presented.

The article discusses the case of an Ethiopian boy in Spain who developed persistent isolation of Salmonella Concord comprising CTX-M-15, SHV-12 and QnrA1. Before he arrived in Madrid, Spain, he was treated with ceftriaxone, piperacillin/tazobactam and amoxicillin/clavulanate. The four Salmonella isolates detected from the boy were resistant to all β-lactams excluding cefoxitin and carbapenems. Furthermore, two of the three Escherichia coli isolates were genetically linked.