Aim of this study was to investigate the genotypic distribution of extended-spectrum β-lactamases (ESBLs) and AmpC enzymes among Escherichia coli isolated from farm animals in Chongqing City. 326 E.coli isolates were obtained from piglets,cattle and chickens.In these isolates,19 ESBLs and 6 AmpC-producing E.coli isolates were detected by preliminary screening and phenotypic identification, and polymerase chain reaction and sequence analysis methods were used to detect ESBLs and AmpCβ-lactamases genes.The results showed that the frequencies of TEM,CTX-M,DHA-1 and CMY-2 genes were 2.15%,5.21%,0.61%and 0.61%,respectively,in E.coli of animal origin in the Chongqing area,and 5 E.coli isolates were found to carry two kinds of genotype.The DHA-1 gene was detected for the first time in a veterinary clinic in China;its GenBank accession number is FJ386455.This study indicated that TEM and CTX-M genes were the predominant genotypes in Chongqing,and the majority of ESBLs and AmpC-producing E.coli isolates were multi-resistant to antibiotics,so they deserve particular attention in veterinary clinics.
