Identification of plasmid-mediated AmpC ?-lactamase in Escherichia coli / 中华检验医学杂志

ABSTRACT

Objective To investigate genotypes and antibiotic resistance of Escherichia coli producing plasmid-mediated AmpC ?-lactamase in Anhui province.Methods A total of 407 clinical isolates of nonrepeated Escherichia coli were collected from different cities in Anhui province.AmpC ?-lactamase producing isolates were identified by cefoxitin three-dimensional test and antibiotic susceptibility was identified by agar dilution test.Plasmid extraction,PCR amplication of corresponding group was performed, followed by sequencing.Results The positive rate of cefoxitin three-dimensional test was 8.1% (33/407), and the prevalence of plasmid-mediated AmpC ?-lactamase was 3.0% (12/407).bla_(CMY-2) gene,bla_(DHA-1) gene and bla_(ACT-2) gene were identified by PCR amplification and confirmed by sequencing in 5 strains,4 strains and 2 strains,respectively.A new CMY genotype was identified,with its sequence revealed 97% identity to the deduced amino acid sequence with previous CMY-2.This is also the first report on ACT-2 genotype in China.The susceptibility test showed that all strains were resistant to cephamycins and piperacillin,and susceptible to imipenem.Two strains of Escherichia coli producing DHA-1 were resistant to fourth-generation cephalosporin.Conclusions CMY-2,DHA-1 and ACT-2 are the most common genotypes in plasmid-mediated AmpC ?-lactamase produced by clinical Escherichia coli isolates in Anhui province. Carbapenems could be the first choice for the treatment of infection caused by AmpC ?-lactamase producers.