Genetic detection of plasmid-mediated AmpC beta-lactamases in Klebsiella pneumoniae strains

OBJECTIVE To retrospectively analyze the genotypes of plasmid-mediated AmpC beta-lactamases of Klebsiella pneumoniae isolated from clinics.METHODS A total of 68 non-duplicate strains of K.pneumoniae resistant to cefoxitin were collected from Jan 2008 to Dec 2008 in our hospital.Three dimensional test was used to screen the producing AmpC enzyme strains,the subtypes were determined by polymerase chain reaction(PCR) and DNA sequencing.RESULTS Totally 18 positive strains were detected by three dimensional test,and all of these showed positive 405 bp bands by PCR.DNA sequencing confirmed that the 18 strains carried DHA-1 type AmpC gene.CONCLUSIONS The identified plasmid-mediated AmpC genes are all DHA genotypes,the resistance genes could be spread among homologous or different genera of bacteria.