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Molecular characterization of extended-spectrum β-lactamase-producing Escherichia coli isolates from chickens in Henan Province, China

¹ Department of Pharmacology and Toxicology, College of Animal Husbandry and Veterinary Science, Henan Agricultural University, Zhengzhou 450002, PR China

² Henan Bureau of Animal Husbandry, Zhengzhou 450002, PR China

Correspondence
Gong-Zheng Hu
yaolilab{at}163.com

Received May 4, 2009
Accepted June 30, 2009

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli has spread rapidly worldwide and poses a serious threat to human and animal health. This study collected 51 non-replicate E. coli isolates from 14 different chicken farms in Henan Province in China from December 2007 to August 2008. The prevalence of ESBL-producing E. coli, molecular characterization of the ESBL-related bla genes, including bla_TEM, bla_SHV and bla_CTX-M, and the susceptibilities of these bacteria to various antimicrobial agents were determined. Thirty-one of the 51 isolates were positive for an ESBL phenotype and 29 of these isolates carried one or more bla genes. Twenty-two isolates harboured bla_TEM genes and 15 isolates carried bla_CTX-M genes (one CTX-M-14, three CTX-M-24 and 11 CTX-M-65). One isolate carried bla_TEM-57; the remaining bla_TEM isolates carried bla_TEM-1 with one silent nucleotide base variation (T18C). We believe that this is the first study to report TEM-57 in E. coli isolates. All isolates harbouring bla_CTX-M-24 and bla_CTX-M-14 and five of the bla_CTX-M-65 isolates also harboured the bla_TEM-1 gene. To our knowledge, this study is the first to describe detection of CTX-M-65-producing E. coli isolated from chickens. None of the isolates contained the bla_SHV gene. Conjugation experiments demonstrated that bla_CTX-M and bla_TEM genes could be transferred to E. coli DH5. The results indicate that ESBL frequency has reached an alarming level in chicken isolates in China, with TEM-1 and CTX-M-65 enzymes being the two predominant β-lactamases detected.

The GenBank/EMBL/DDBJ accession numbers for the sequences of the majority of the β-lactamases from the 31 isolates in this study are FJ405191–FJ405214 and FJ812104–FJ812110.