Abstract
Background: Extended-spectrum beta-lactamases (ESBLs) are an increasingly important cause of resistance in Gram-negative bacteria throughout the world.
Aim: We investigated the clinical and molecular epidemiology of infections caused by ESBL-producing Enterobacteriaceae in a UK hospital, to identify the types of ESBL produced and risk factors for acquisition.
Methods: Between July 2008 and June 2009, all patients yielding ESBL-producing Enterobacteriaceae from any clinical specimen were prospectively investigated using a questionnaire. API20E was used for bacterial identification; susceptibility testing and ESBL production were assessed by BSAC disc diffusion and cefpodoxime-clavulanate synergy tests, respectively. Polymerase chain reaction was used to screen a subset of isolates for bla(CTX-M) genes, to assign Escherichia coli isolates to their phylogenetic groups, and to identify members of the uropathogenic ST131 lineage.
Results: The overall prevalence of ESBL producers among clinical samples yielding Enterobacteriaceae was 1%; ESBL producers, obtained from 124 patients, were E. coli (N = 105), Klebsiella pneumoniae (N = 12), and others (N = 7). The main risk factors identified include recent antibiotic use (93%) and presence of a urinary catheter (24%). CTX-M group 1 ESBLs dominated (in 59 of 78, 76%, isolates studied). Most E. coli (35 of 56 tested) were phylogroup B2; of these, 23 belonged to the ST131 clone, 12 were phylogroup D, and four each belonged to phylogroups A and B1.
Conclusion: ESBLs are an uncommon but significant problem in north-west Cambridgeshire. CTX-M-type enzymes were found in 75% of ESBL-positive isolates. All but two patients had at least one recognized risk factor. This study supports the requirement for interventions to reduce inappropriate urinary catheterization and antibiotic prescribing. (c) 2012 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.