title: Prevalence, molecular characterization, and phenotypic confirmation of extended-spectrum beta-lactamases in Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca at the Radboud University Nijmegen Medical Centre in The Netherlands.
abstract: The prevalence and molecular types of extended-spectrum beta-lactamases (ESBLs) were determined during a 1-year period in unselected clinical nonduplicate isolates of Escherichia coli (n = 1,738), Klebsiella pneumoniae (n = 436), and Klebsiella oxytoca (n = 208), cultured at the University Medical Centre Nijmegen, The Netherlands. Isolates identified as ESBL producer by the Phoenix automated system were collected prospectively and subjected to molecular analysis for the most common ESBLs TEM, SHV, and CTX-M, as well as OXA and GES. Both the Etest ESBL and double-disk synergy test were performed as confirmatory tests. The estimated prevalence of ESBLs was 2.1% in E. coli, 5.2% in K. pneumoniae, and 2.4% in K. oxytoca. TEM-12 and -26, SHV-5 and -12, and CTX-M groups 1 and 9 were the most frequent ESBLs found. Isolates identified as ESBLs by the Phoenix were confirmed by polymerase chain reaction (PCR) in only 42%. In ESBL PCR-positive E. coli and K. pneumoniae, both confirmatory tests were positive in 95% of the isolates. In 28% of the Etest and 13% of the double-disk synergy test-positive isolates, PCR could not detect any ESBL gene. In these cases, other resistance mechanisms may play a role. Confirmatory tests were unreliable for K. oxytoca. A previously described mutation in the K1 enzyme was detected in one ceftazidime-resistant K. oxytoca. The prevalence of ESBLs in The Netherlands is increasing. The predominant molecular types of ESBLs detected were comparable to other studies. Phoenix ESBL results need to be confirmed as advocated by ESBL detection guidelines.
authors.affiliation: Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Postbus 9101, 6500 HB Nijmegen, The Netherlands. p.sturm@mmb.umcn.nl
authors.forename: Patrick D J
authors.initials: PD
authors.lastname: Sturm
authors.forename: Els T M
authors.initials: ET
authors.lastname: Bochum
authors.forename: Sacha V M
authors.initials: SV
authors.lastname: van Mook-Vermulst
authors.forename: Cindy
authors.initials: C
authors.lastname: Handgraaf
authors.forename: Twan
authors.initials: T
authors.lastname: Klaassen
authors.forename: Willem J G
authors.initials: WJ
authors.lastname: Melchers
mesh_terms: D000046:Academic Medical Centers; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004755:Enterobacteriaceae / Q000187:drug effects / Q000235:genetics; D004756:Enterobacteriaceae Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D005798:Genes, Bacterial; D006801:Humans; D041121:Klebsiella oxytoca / Q000187:drug effects / Q000235:genetics; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000235:genetics; D008826:Microbial Sensitivity Tests / Q000379:methods; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D017422:Sequence Analysis, DNA; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics*; D047090:beta-Lactams / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D047090:beta-Lactams; D001618:beta-Lactamases