Detection of plasmid-mediated ampc β-lactamase genotypes of Klebsiella pneumoniae and Escherichia coli.

Objective To explore the epidemic status of plasmid-mediated AmpC β-lactamase genotype from the clinical isolates of Klebsiella pneumoniae and Escherichia coli in Taizhou.Methods Microbiological identification was performed with the VITEK 60 System and β-lactamases(ESBLs) were detected in accordance with the confirmatory test recommended by NCCLS.Suspected positive strains of AmpC β-lactamase were screened with cefoxitin disk diffusion.The genotypes and phenotypes were analyzed by cefoxitin three-dimensional test,conjugation test and PCR sequencing.Results Of the 299 isolates,the rate of ESBLs was 19.73%(59/299),the positive rate was 12.04%(36/299) when screened with AmpC β-lactamase disk diffusion and all the 36 were positive strains of ESBLs.15 of the strains were confirmed to be AmpC β-lactamase positive through the three-dimensional test,with a rate of 5.02%(15/299).From them,15 conjugants were produced by conjugation,and confirmed to be much the same as the original phenotype.In plasmid-mediated AmpC β-lactamases,13 were CIT and 2 were DHA.Conclusion In the plasmid-born genes from the clinical isolates of K.pneumoniae and E.coli in Taizhou,their genotype is mainly CIT and next comes DHA.AmpC gene may exist in the same plasmid as the gene encoding ESBLs and the plasmids of encoded AmpC β-lactamase can transmit between bacteria.