Abstract

The objective of this study was to characterise the β-lactamase genes of cephalosporin-resistant Escherichia coli isolated from farm animals in Guangdong Province of China. Of 592 E. coli isolates recovered from farm animals from 2003–2005, 50 (8.4%) showed cephalosporin resistance. Polymerase chain reaction and sequencing analysis showed that 14 isolates (2.4%) from chickens, ducks, pigs and partridges were positive for the blaCTX-M gene (10 for blaCTX-M-14 and 4 for blaCTX-M-27). CMY-2 was detected for the first time in mainland China in six E. coli isolates (1.0%) from chickens and goose. Except for one isolate, blaCTX-M- and blaCMY-2-containing isolates also harboured the blaTEM-1b gene. Conjugation experiments demonstrated that the blaCTX-M and blaTEM genes could be transferred to E. coli DH5α. Pulsed-field gel electrophoresis (PFGE) showed that the 14 CTX-M-producing isolates belonged to 12 different types. Two isolates (one from a chicken, the other from a pig) containing CTX-M-14 showed indistinguishable PFGE patterns, indicating clonal dissemination of this strain among animals from different farms. This study describes for the first time the emergence of CTX-M- and CMY-2-producing E. coli among farm animals in China, with the CTX-M-9 group being the predominant extended-spectrum β-lactamase detected.

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