Virulence profiles of bacteremic extended-spectrum β-lactamase-producing Escherichia coli: association with epidemiological and clinical features

There is scarce data about the importance of phylogroups and virulence factors (VF) in bloodstream infections (BSI) caused by extended-spectrum β-lactamase-producing Escherichia coli (ESBLEC). A prospective multicenter Spanish cohort including 191 cases of BSI due to ESBLEC was studied. Phylogroups and 25 VF genes were investigated by PCR. ESBLEC were classified into clusters according to their virulence profiles. The association of phylogropus, VF, and clusters with epidemiological features were studied using multivariate analysis. Overall, 57.6%, 26.7%, and 15.7% of isolates belonged to A/B1, D and B2 phylogroups, respectively. By multivariate analysis (adjusted OR [95% CI]), virulence cluster C2 was independently associated with urinary tract source (5.05 [0.96–25.48]); cluster C4 with sources other than urinary of biliary tract (2.89 [1.05–7.93]), and cluster C5 with BSI in non-predisposed patients (2.80 [0.99–7.93]). Isolates producing CTX-M-9 group ESBLs and from phylogroup D predominated among cluster C2 and C5, while CTX-M-1 group of ESBL and phylogroup B2 predominantes among C4 isolates. These results suggest that host factors and previous antimicrobial use were more important than phylogroup or specific VF in the occurrence of BSI due to ESBLEC. However, some associations between virulence clusters and some specific epidemiological features were found.

Increased raw poultry meat colonization by extended spectrum beta-lactamase-producing Escherichia coli in the south of Spain

The present study was conducted to assess the prevalence of retail chicken and turkey meat colonized by extended-spectrum beta-lactamase-producing Escherichia coli (ESBLEC) in Seville, Spain. ESBLEC recovered from meat samples purchased in 2010 were characterized by specific PCR analysis for bla genes, phylogenetic groups and subgroups (genotypes) and O25b/pabB/B2 traits of ST131. Results were compared with those obtained in a previous study in 2007, when a high percentage of retail meat samples were found to be colonized by ESBLEC. The prevalence of retail poultry meat colonized by ESBLEC increased from 62.5% in 2007 to 93.3% in 2010 (p=0.005). Non-pathogenic B1 and A(1) genotypes accounted for more than 60% of the 60 isolates recovered. Sequence type ST131 or B2 phylogroup isolates were not detected. Clonal relatedness was detected in just 2 CTX-M-1-producing isolates from 2 chicken samples belonging to phylogenetic group A, genotype A(1). There continued to be a significantly high quinolone resistance, with 85.4% and 32.2% of isolates showing resistance to nalidixic acid and ciprofloxacin, respectively. SHV-12 was the most common ESBL harbored by E. coli, although it has decreased in prevalence since 2007. Meanwhile, CTX-M ESBLs prevalence has increased. We conclude that the trend of colonization by ESBLECs-particularly CTX-M-producing isolates-in raw poultry meat has increased in a short period of time in our area.

Impact of changes in CLSI and EUCAST breakpoints for susceptibility in bloodstream infections due to extended-spectrum β-lactamase-producing Escherichia coli

The impact of recent changes in and discrepancies between the breakpoints for cephalosporins and other antimicrobials, as determined by CLSI and European Committee on Antimicrobial Susceptibility Testing (EUCAST), was analysed in patients with bloodstream infections caused by extended-spectrum β-lactamase (ESBL) producing Escherichia coli in Spain, was analysed. We studied a cohort of 191 episodes of bloodstream infection caused by ESBL-producing E. coli in 13 Spanish hospitals; the susceptibility of isolates to different antimicrobials was investigated by microdilution and interpreted according to recommendations established in 2009 and 2010 by CLSI, and in 2011 by EUCAST. Overall, 58.6% and 14.7% of isolates were susceptible to ceftazidime, and 35.1% and 14.7% to cefepime using the CLSI-2010 and EUCAST-2009/2011 recommendations, respectively (all isolates would have been considered resistant using the previous guidelines). Discrepancies between the CLSI-2010 and the EUCAST-2011 recommendations were statistically significant for other antimicrobials only in the case of amikacin (98.4% versus 75.9% of susceptible isolates; p <0.01). The results varied depending on the ESBL produced. No significant differences were found in the percentage of patients classified as receiving appropriate therapy, following the different recommendations. Four out of 11 patients treated with active cephalosporins according to CLSI-2010 guidelines died (all had severe sepsis or shock); these cases would have been considered resistant according to EUCAST-2011. In conclusion, by using current breakpoints, extended-spectrum cephalosporins would be regarded as active agents for treating a significant proportion of patients with bloodstream infections caused by ESBL-producing E. coli.

Assessment of the presence of extended-spectrum beta-lactamase-producing Escherichia coli in eggshells and ready-to-eat products

The principal objective of this study was to assess whether chicken eggshells may be contaminated by ESBL-producing E. coli (ESBLC). Additional analyses were carried out to determine if ESBLEC could be detected in other foodstuffs such as cooked poultry or fresh vegetables. Seventy-two eggshells from different supermarkets and stores as well as 32 salads, 30 samples of cooked poultry and six samples of chicken-based pet food samples were analysed. Characterization of ESBL was performed by PCR and sequencing. Antimicrobial resistance was determined by disk diffusion method. Phylogenetic group was assigned by multiplex-PCR. No ESBLEC was isolated from chicken eggshells, cooked chicken and pet food. One SHV-12-producing E. coli was isolated from a salad sample. This is the first study to analyse chicken eggs in an area where there is a high prevalence of ESBLEC in retail chicken meat.

Characterisation of clinical and food animal Escherichia coli isolates producing CTX-M-15 extended-spectrum β-lactamase belonging to ST410 phylogroup A

Seven phylogroup A CTX-M-15-producing Escherichia coli isolates recovered from clinical and meat samples were further characterised. All of them belonged to sequence type ST410. Only 2 of the 22 virulence genes investigated were detected. All isolates carried the fimH gene encoding type 1 fimbriae, and five isolates harboured the iucD gene encoding aerobactin siderophore. A group of five isolates showed 81.2% similarity by pulsed-field gel electrophoresis (PFGE), comprising three clinical isolates belonging to ONT:H9 and two food isolates belonging to O55:H9. Different HpaI digestion patterns were observed for plasmids, but all of them belonged to IncFIB group and harboured bla(CTX-M-15) associated with bla(OXA-1), bla(TEM), tetA, catB3 and aac(6')-Ib surrounded by an identical genetic environment. These findings showed the possibility of lateral gene transfer of bla(CTX-M-15) as well as other antibiotic resistance determinants between low-virulence food and clinical isolates.

Extended-spectrum and CMY-type beta-lactamase-producing Escherichia coli in clinical samples and retail meat from Pittsburgh, USA and Seville, Spain

Infections due to Escherichia coli producing extended-spectrum beta-lactamase (ESBL) or CMY-type beta-lactamase (CMY) are increasingly observed in non-hospitalized patients. The origin of these organisms is uncertain, but retail meat contaminated with E. coli may be a source. In the present study, clinical information and strains collected from patients infected or colonized with ESBL-producing and CMY-producing E. coli at hospitals in Pittsburgh, USA and Seville, Spain were investigated. Retail meat purchased in these cities was also studied for the presence of these organisms. Twenty-five and 79 clinical cases with ESBL-producing E. coli and 22 cases and one case with CMY-producing E. coli were identified in Pittsburgh and Seville, respectively. Among them all, community-acquired and healthcare-associated cases together constituted 60% of the cases in Pittsburgh and 73% in Seville. Community-acquired cases were more common in Seville than in Pittsburgh (49% vs. 13%; p <0.001). ESBL-producing and CMY-producing E. coli isolates were commonly recovered from the local retail meat. In particular, 67% (8/12) of retail chickens in Seville and 85% (17/20) of those in Pittsburgh contained ESBL-producing and CMY-producing E. coli isolates, respectively. Among the ESBL-producing isolates, CTX-M and SHV were the most common ESBL types in both clinical and meat isolates. Approximately half of the ESBL-producing and CMY-producing E. coli isolates from meat belonged to phylogenetic groups associated with virulent extra-intestinal infections in humans. Community and healthcare environments are now significant reservoirs of ESBL-producing and CMY-producing E. coli. Retail meat is a potential source of these organisms.

Comparative assessment of inoculum effects on the antimicrobial activity of amoxycillin-clavulanate and piperacillin-tazobactam with extended-spectrum beta-lactamase-producing and extended-spectrum beta-lactamase-non-producing Escherichia coli isolates

A significant inoculum-size effect has been observed with piperacillin-tazobactam, and has been associated with beta-lactamase production in extended-spectrum beta-lactamase (ESBL) producers. This association has not been previously studied in the case of amoxycillin-clavulanate. Piperacillin-tazobactam and amoxycillin-clavulanate were compared, using high inocula of susceptible strains either harbouring ESBLs or not. Two non-ESBL-producing and 15 amoxycillin-clavulanate-susceptible and piperacillin-tazobactam-susceptible ESBL-producing Escherichia coli isolates, and their respective transconjugants, were tested in dilution susceptibility tests using standard and 100-fold higher inocula. Three ESBL-producing strains and E. coli ATCC 25922 were selected for time-kill studies using standard and high initial inocula. At high inocula, MICs of piperacillin increased >eight-fold for non-ESBL-producing strains, and MICs of piperacillin-tazobactam (8:1 ratio or with tazobactam fixed at 4 mg/L) increased>eight-fold for all ESBL-producing strains. However, amoxycillin MICs were not affected by a high inoculum with non-ESBL-producing strains, whereas the MICs of amoxycillin-clavulanate (2:1 and 4:1) increased <or=four-fold for ESBL producers, using the broth and agar dilution methods. In kinetic studies at a high inoculum, amoxycillin and amoxycillin-clavulanate were bactericidal against E. coli ATCC 25922, whereas piperacillin and piperacillin-tazobactam yielded decreases of <1 log(10) CFU/mL. Similarly, at a high inoculum, only amoxycillin-clavulanate was able to maintain bactericidal rates of killing over 24 h against the ESBL-positive E. coli isolates. The stability of amoxycillin-clavulanate and the contrasting results obtained with piperacillin-tazobactam against high inocula of ESBL-non-producing and ESBL-producing E. coli strains appear to be related to aspects other than the amount of beta-lactamase production.

Acquisition and cross-transmission of Staphylococcus aureus in European intensive care units

OBJECTIVE

To study the acquisition and cross-transmission of Staphylococcus aureus in different intensive care units (ICUs).

METHODS

We performed a multicenter cohort study. Six ICUs in 6 countries participated. During a 3-month period at each ICU, all patients had nasal and perineal swab specimens obtained at ICU admission and during their stay. All S. aureus isolates that were collected were genotyped by spa typing and multilocus variable-number tandem-repeat analysis typing for cross-transmission analysis. A total of 629 patients were admitted to ICUs, and 224 of these patients were found to be colonized with S. aureus at least once during ICU stay (22% were found to be colonized with methicillin-resistant S. aureus [MRSA]). A total of 316 patients who had test results negative for S. aureus at ICU admission and had at least 1 follow-up swab sample obtained for culture were eligible for acquisition analysis.

RESULTS

A total of 45 patients acquired S. aureus during ICU stay (31 acquired methicillin-susceptible S. aureus [MSSA], and 14 acquired MRSA). Several factors that were believed to affect the rate of acquisition of S. aureus were analyzed in univariate and multivariate analyses, including the amount of hand disinfectant used, colonization pressure, number of beds per nurse, antibiotic use, length of stay, and ICU setting (private room versus open ICU treatment). Greater colonization pressure and a greater number of beds per nurse correlated with a higher rate of acquisition for both MSSA and MRSA. The type of ICU setting was related to MRSA acquisition only, and the amount of hand disinfectant used was related to MSSA acquisition only. In 18 (40%) of the cases of S. aureus acquisition, cross-transmission from another patient was possible.

CONCLUSIONS

Colonization pressure, the number of beds per nurse, and the treatment of all patients in private rooms correlated with the number of S. aureus acquisitions on an ICU. The amount of hand disinfectant used was correlated with the number of cases of MSSA acquisition but not with the number of cases of MRSA acquisition. The number of cases of patient-to-patient cross-transmission was comparable for MSSA and MRSA.

[Comparison of 3 methods for determining sensitivity to imipenem and meropenem in Acinetobacter baumannii with a carbapenem-heteroresistant phenotype]

INTRODUCTION

We assessed agreement among 3 assays for determining susceptibility to imipenem (IMP) and meropenem (MPM) of Acinetobacter baumannii (Ab) heteroresistant to carbapenems (Hr-CP).

METHODS

Thirty Ab clinical isolates belonging to 6 clones (REP-PCR) were studied, in which IMP and MPM MICs were between < or = 1 and > or = 8 mg/l by Wider system. MICs determined by Wider were compared with those obtained by microdilution (MD) and E-test. Errors in the clinical category were determined considering MD as the reference method.

RESULTS

Twenty-five Ab were Hr-CP (growth of resistant colonies within the inhibition area of disks and E-test strips). Agreement for the MICs (+/- 1log(2)) in Hr-CP colonies was as follows: Wider vs. MD (96% IMP, 100% MPM), Wider vs. E-test (50% IMP, 64% MPM), MD vs. E-test (64% IMP, 60% MPM). Major errors were not observed. Minor errors and moderate errors for IMP included Wider vs. MD (40% and 0%), E-test vs. MD (40% and 12%), and disks vs. MD (36% and 8%). Agreement for the MICs considering colonies growing within the inhibition areas (E-test and disks) was Wider vs. E-test (8% IMP, 12% MPM), and MD vs. E-test (8% IMP and MPM). Major errors were not observed in this case either; minor errors and moderate errors for IMP were seen in E-test vs. MD (40% and 48%), and disks vs. MD (40% and 48%).

CONCLUSION

Susceptibility testing methods based on microdilution (Wider system and MD) are not useful to detect subpopulations of Ab Hr-CP.

Faecal carriage of extended-spectrum beta-lactamase-producing Escherichia coli: prevalence, risk factors and molecular epidemiology

OBJECTIVES

The aim of this study was to investigate the epidemiology of faecal carriage of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in the community.

PATIENTS AND METHODS

Faecal carriage with ESBL-producing E. coli was studied in 53 outpatients with urinary tract infection (UTI) due to these organisms, 73 household members, 32 non-household relatives and 54 unrelated patients. Clonal relatedness of the isolates was investigated using repetitive extragenic palindromic-PCR and PFGE, and ESBLs were characterized by PCR and sequencing. Multivariate analysis was performed to investigate risk factors for faecal carriage.

RESULTS

The prevalence of faecal carriage was 67.9% in patients with UTI, 27.4% in household members, 15.6% in non-household relatives and 7.4% in unrelated patients. Being a relative of a patient with UTI was independently associated with an increased risk of being a carrier. Among the relatives, multivariate analysis showed that those eating their main meal outside their own home >15 days during the previous month were less likely to be faecal carriers (OR = 0.2; 95% CI: 0.06-0.6; P = 0.007). The faecal isolates of patients with UTI were CTX-M-producers in 66.6% and SHV-producers in 33.3% of the cases, while the percentages for other population groups were 40% to 55.5% and 50% to 75%, respectively. Of the 19 families with >1 carrier member, 8 families had 2 members who shared clonally related isolates, 8 families had 2 members carrying different clones producing the same enzymes and there were 3 families where all members had different enzyme-producing clones.

CONCLUSIONS

Our results suggest that both acquisition from a common source and person-to-person transmission might contribute to ESBL dissemination.

[Activity of fosfomycin against extended-spectrum beta-lactamase producing Escherichia coli and Klebsiella pneumoniae]

INTRODUCTION

Infection due to extended-spectrum beta-lactamase (ESBL)-producing microorganisms is an emerging problem in the community; a high proportion of these microorganisms have been isolated from urine samples of women with uncomplicated urinary tract infections (UTI). The options for oral treatment of uncomplicated UTI are limited because of the multiple drug resistance typical of ESBL-producing strains.

METHODS

The in vitro activity of fosfomycin (FOS) was determined against 428 ESBL-producing strains, including 290 (68%) E. coli and 138 (32%) K. pneumoniae. Activity of fosfomycin was compared with that of amoxicillin-clavulanate (AMC), ciprofloxacin (CIP) and cotrimoxazole (SxT). MICs of AMC, CIP, and SxT, and detection of ESBL production were tested by the broth microdilution method, whereas FOS MICs were determined by the agar dilution method. ESBLs were characterized by isoelectric focusing, polymerase chain reaction (PCR) and direct sequencing of encoding genes. The genetic relationship among the isolates was determined by REP-PCR.

RESULTS

Among the 428 ESBL-producing isolates studied, 417 (97.4%) were susceptible to FOS (MIC < or = 64 microg/mL). The resistance rate of E. coli to FOS was 0.3%, and was lower than resistance to AMC (11.7%), whereas the resistance rate of K. pneumoniae was 7.2% and was equal to resistance to AMC. SxT and CIP were the least active antibiotic agents against ESBL-producing isolates (sensitivity < 50%). There were no differences in fosfomycin activity against strains expressing different types of ESBLs.

CONCLUSION

Fosfomycin showed maintained activity against ESBL-producing strains and did not present co-resistance with other antimicrobial groups.