Differences in the antibiotic susceptibility of human Escherichia coli with poultry-associated and non-poultry-associated extended-spectrum beta-lactamases.

The concurrent presence of bla CTX-M-1 and bla TEM-52 genes on similar plasmids of Escherichia coli isolated from poultry, chicken meat and humans supports the occurrence of food-borne transmission of extended-spectrum beta-lactamase (ESBL) genes. ESBL-producing E. coli (ESBL-E. coli) are most frequently detected in hospitalised patients and are known to spread in healthcare settings. We hypothesised that poultry-associated (PA) ESBL genes are predominant in the community, where acquisition is fuelled by food contamination, whereas non-PA ESBL genes are predominant in hospitals, with acquisition fuelled by cross-transmission. Then, differences in antimicrobial selective pressure in hospitals and poultry would create differences in co-resistance between PA and non-PA ESBL-E. coli. We, therefore, determined the prevalence and co-resistance of PA and non-PA ESBL-E. coli in community-acquired and nosocomial urinary tract infections in humans and bla CTX-M-1 and bla TEM-52 isolates from poultry. A total of 134 human ESBL-E. coli urine isolates were included in this study. Isolates containing bla CTX-M-1 or bla TEM-52 were considered to be PA, with the remainder being non-PA. Also, 72 poultry ESBL-E. coli were included. Minimum inhibitory concentration (MIC) values were determined by broth microdilution. The prevalence of PA ESBL genes in isolates obtained in general practice and hospitals was 28 % versus 30 % (n.s.). Human PA ESBL-E. coli were more frequently susceptible to ciprofloxacin (51 % vs. 25 %; p = 0.0056), gentamicin (86 % vs. 63 %; p = .0.0082), tobramycin (91 % vs. 34 %; p = 0.0001) and amikacin (98 % vs. 67 %; p = 0.0001) compared to human non-PA ESBL-E. coli. PA ESBL-E. coli are not more prevalent in community acquired than nosocomial urine samples, but are more often susceptible to ciprofloxacin and aminoglycosides than non-PA ESBL-E. coli. This does not support the existence of different reservoirs of ESBL genes.

The changing epidemiology of bacteraemias in Europe: trends from the European Antimicrobial Resistance Surveillance System.

We investigated bacteraemia trends for five major bacterial pathogens, Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, Enterococcus faecalis and Enterococcus faecium, and determined how expanding antimicrobial resistance influenced the total burden of bacteraemias in Europe. Aetiological fractions of species and antibiotic phenotypes were extracted from the European Antimicrobial Resistance Surveillance System (EARSS) database for laboratories, which consistently reported between 2002 and 2008. Trend analyses used generalized linear models. Robustness of results was assessed by iterative analysis for different geographic regions. From 2002 to 2008, the overall number of reports increased annually by 6.4% (95% confidence interval (CI) 6.2-6.5%), from 46 095 to 67 876. In the subset of laboratories providing denominator information, the overall incidence increased from 0.58/1000 patient-days to 0.90/1000 patient-days (7.2% per year; 95% CI 6.9-7.5%). The frequency of reported bacteraemia isolates of S. aureus and Streptococcus pneumoniae increased moderately, while increase in E. coli and Enterococcus faecium was more pronounced. Bacteraemias caused by methicillin-resistant S. aureus increased until 2005 (7.6% per year; 95% CI 6.1-9.1%), and then decreased (-4.8% per year; 95% CI -6.1 to -3.5%), whereas the number attributable to methicillin-sensitive S. aureus increased continuously (3.4% per year; 95% CI 3.0-3.7). Increasing rates of E. coli were mainly caused by antibiotic-resistant phenotypes. Our data suggest that the burden of bacterial bloodstream infection has been increasing for all species during EARSS surveillance. Trends were mainly driven by resistant strains and clearly dissociated between resistant and susceptible isolates. It appears that infections with resistant clones add to rather than replace infections caused by susceptible bacteria. As a consequence, expansion of antibiotic resistance creates an additional strain on healthcare systems.

Multi-centre evaluation of a phenotypic extended spectrum ß-lactamase detection guideline in the routine setting.

This study aimed to evaluate the routine setting performance of a guideline for phenotypic detection of extended spectrum ß-lactamases (ESBLs) in Enterobacteriaceae, recommending ESBL confirmation with Etest or combination disc for isolates with a positive ESBL screen test (i.e. cefotaxime and/or ceftazidime MIC >1 mg/L or an automated system ESBL warning). Twenty laboratories submitted 443 Enterobacteriaceae with a positive ESBL screen test and their confirmation test result (74%Escherichia coli, 12%Enterobacter cloacae, 8%Klebsiella pneumoniae, 3%Proteus mirabilis, 2%Klebsiella oxytoca). Presence of ESBL genes was used as reference test. Accuracy of local phenotypic ESBL detection was 88%. The positive predictive value (PPV) of local screen tests was 70%, and differed per method (Vitek-2: 69%, Phoenix: 68%, disc diffusion: 92%), and species (95%K. pneumoniae-27%K. oxytoca). A low PPV (3%) was observed for isolates with automated system alarm but third-generation cephalosporin MICs <2 mg/L. Local ESBL confirmation had a PPV and negative predictive value (NPV) of 93% and 90%, respectively. Compared with centrally performed confirmation tests, 7% of local tests were misinterpreted. Combination disc was more specific than Etest (91% versus 61%). Confirmation tests were not reliable for P. mirabilis and K. oxytoca (PPV 33% and 38%, respectively, although NPVs were 100%). In conclusion, performance of Etests could be enhanced by education of technicians to improve their interpretation, by genotypic ESBL confirmation of P. mirabilis and K. oxytoca isolates with positive phenotypic ESBL confirmation, and by interpreting isolates with a positive ESBL alarm but an MIC <2 mg/L for cefotaxime and ceftazidime as ESBL-negative.

Evaluation of a commercial microarray as a confirmation test for the presence of extended-spectrum ß-lactamases in isolates from the routine clinical setting.

Since the diagnostic characteristics of the Check-KPC ESBL microarray as a confirmation test on isolates obtained in a routine clinical setting have not been determined, we evaluated the microarray in a random selection of 346 clinical isolates with a positive ESBL screen test (MIC >1 mg/L for cefotaxime or ceftazidime or an ESBL alarm from the Phoenix or Vitek-2 expert system) collected from 31 clinical microbiology laboratories in the Netherlands in 2009. Using sequencing as the reference method the sensitivity of the microarray was 97% (237/245), the specificity 98% (97/99), the positive predictive value 99% (237/239) and the negative predictive value 92% (97/105).