Molecular epidemiology and antimicrobial resistance pattern of extended-spectrum-β-lactamase-producing Enterobacteriaceae in Glasgow, Scotland

Abstract

Objectives: To establish the molecular epidemiology and antimicrobial resistance pattern of extendedspectrum β-lactamase (ESBL)-producing Enterobacteriaceae harbouring bla CTX-M in Glasgow, Scotland. Methods: During a 12 week period, Enterobacteriaceae isolates obtained from urine samples were collected and susceptibility testing performed. Isolates were screened for the presence of bla CTX-M by multiplex PCR and selected Escherichia coli genes were subsequently sequenced. PFGE analysis was performed on selected E. coli isolates in order to identify clonal relationships. Results: There were 155 phenotypically confirmed non-duplicate Enterobacteriaceae isolates obtained from urine samples. bla CTX-M was identified in 131/155 (84.5%) of the ESBL-producing isolates, with CTX-M group 1 enzymes accounting for 103/131 (78.6%) of these. The remaining 24 isolates carried other bla CTX-M types, including CTX-M group 2, CTX-M group 9 and an unidentifiable combination designated CTX-M group G2/Gx. A sample of 46/97 (47.4%) CTX-M-positive E. coli isolates was chosen for PFGE and demographic information regarding the source of the isolates was collated. Eight E. coli clusters were identified by PFGE; however, they did not achieve the 85% cut-off to demonstrate clonality. Nitrofurantoin resistance was significantly greater in the E. coli isolates expressing a non-CTX-M group 1 ESBL when compared with the E. coli isolates expressing a CTX-M group 1 ESBL. Conclusions: As seen in other British studies, bla CTX-M has become the predominant ESBL type in Glasgow, Scotland. The PFGE results show that four different CTX-M groups appear to be circulating in the community and within all four hospitals in the locality. There is little correlation between strain genotype and CTX-M group, thus it is unlikely that cross-infection alone is the driver. It is possible that plasmid migration of CTX-M genes within the E. coli population is occurring. © The Author 2011. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.