Resistance of strains producing extended-spectrum β-lactamases and genotype distribution among Escherichia coli in China

Extended-spectrum β-lactamases (esbls) are an increasing cause of resistance to third-generation cephalosporins in enterobacteriaceae. in order to investigate the resistance of escherichia coli (e. coli) strains producing esbls and the genotyping of esbls from swine in heilongjiang province in china,220 e. coli strains were isolated consecutively from health swine herds during may to november 2010. results of antimicrobial susceptibility test showed that most of the isolates were highly susceptible to polymyxin b and aztreonam,but high resistant incidence rates were exhibited to ampicillin. the incidence of esbl-producing strains was 36.37% among escherichia coli (80/220). the genotypes of esbls were analyzed by polymerase chain reaction (pcr),dna sequencing. pcr and sequence analysis showed that eighty strains produced four type of esbls,including ctx-m (27 strains),tem (36 strains),shv (2 strains),oxa (2 strains). the resistance of e. coli strains producing esbls in heilongjiang province was a serious issue,and tem and ctx-m type esbls were the most common genotypes. some esbls-producing escherichia coli strains produced more than one type of β-lactamases. these data confirm that esbl producers are common among nursery strains of escherichia coli in heilongjiang province in china. it is important to monitor such strains closely and prevent their spread. copyright 2012 zoological society of pakistan.