Predominance and genetic diversity of community- and hospital-acquired CTX-M extended-spectrum beta-lactamases in

Objectives: This study was conducted to detect the presence of extended-spectrum b-lactamase (ESBL)-producing Enterobacteriaceae within the faecal flora of both community- and hospital-based patients in York and to characterize the blaTEM, blaSHV and blaCTX-M genes present in these isolates. Methods: One thousand faeces samples were collected and screened at York Hospital during October–December 2003. Ninety-five non-duplicate Enterobacteriaceae isolates resistant to third-gener-ation cephalosporins were recovered; 22 isolates were selected for further study on the basis of a posi-tive double disc diffusion test for ESBL production. Antibiotic susceptibility testing was performed to a range of antibiotics. The TEM, SHV and CTX-M genes were detected by PCR and the DNA sequenced. Results: The distribution of ESBL-positive isolates from the hospital and community was 1.4:1. These included nine Escherichia coli, seven Enterobacter cloacae, four Citrobacter freundii and a single isolate each of Klebsiella spp. and Salmonella spp. A total of 17 isolates contained blaCTX-M (five blaCTX-M-15, three blaCTX-M-14 and nine blaCTX-M-9). ISEcp1 was present in isolates expressing CTX-M-14 and-15, but was absent upstream of In60-associated blaCTX-M-9. E. coli isolates also contained either a blaTEM-1 or blaTEM-2, whereas six of the E. cloacae carried blaSHV-12 and the Klebsiella spp. blaSHV-36 in addition to blaCTX-M-9. The single Salmonella spp. carried blaSHV-12