Prevalence of plasmid-mediated AmpC beta-lactamases in the Klebsiella pneumoniae strains isolated in Changsha

Objective To study the plasmid-mediated AmpC β-lactamases and the genotypes of K.pneumoniae in Changsha region.MethodsA total of 110 non-duplicate strains of K.pneumoniae were isolated from October 2007 to July 2008 in the three affiliated hospitals of Central South University in Changsha,Hunan province.Cefoxitin disk diffusion method was used to screen the K.pneumoniae for phenotypic AmpC enzyme.Multiple PCR method was adopted to test ampC genotypes of the AmpC enzyme-positive K.pneumoniae strains.ResultsOf all the 110 clinical isolates of K.pneumoniae,24 were not sensitive to cefoxitin disk,21 showed positive 405 bp bands by multiple PCR.Specific PCR confirmed that the 21 strains carried DHA type ampC gene.The prevalence of plasmid-mediated AmpC enzyme in K.pneumoniae was 19.1%(21/110).ConclusionsThe prevalence of plasmid-mediated AmpC enzyme in K.pneumoniae isolates is relatively high in Changsha area.The identified plasmid-mediated ampC genes are all DHA genotype.