Distribution of plasmid-mediated AmpC beta-lactamase in Escherichia coli

Objective To investigate the genotype and distribution of plasmid-mediated AmpC β-lactamases in Escherichia coli in Henan. Methods 380 Escherichia coli were detected by standard disc diffusion method which was used as screen test for AmpC β-lactamase.Multiplex polymerase chain reaction(PCR),type-specific PCR,clone,sequencing,isoelectric focusing analysis,conjugation and enterobacterial repetitive intergenic consensus-2(ERIC-2) PCR were performed on positive strains to determine the genotype,the isoelectric point,the transitivity of plasmid and the homology of AmpC β-lactamases.Results 8 of 380 Escherichia coli strains(2.1%) were AmpC β-lactamases-positive strains.All of them were bla_DHA which were confirmed by sequencing.The results of ERIC-2 PCR analysis indicated that the prevalences of plasmid-mediated AmpC β-lactamase were not due to epidemic strains.Conclusions The clinical isolate of Escherichia coli producing DHA-1 type plasmid-mediated AmpC β-lactamase was found in Henan.The prevalence were not due to epidemic strains.