A study on resistance and genotypes of plasmid-mediated AmpC β-lactamase-producing Klebsiella pneumoniae

Objective To investigate the resistance of cefoxitin-resistant Klebsiella pneumoniae(K.pneu)and genotypes of plasmid-mediated AmpC β-lactamases.Methods A total of 49 clinical isolates of cefoxintin-resistant non-repetitive K.pneu were detected by three-dimensional extract test for AmpC β-Lactamases.The susceptibility to antimicrobial agents of the isolates was studied by agar dilution method.Multiplex PCR was used to amplify plasmid-mediated AmpC β-lactamases gene and differentiate genotypes after extracting plasmid from cefoxitin-resistant clinical strains,and the PCR products were sequenced.Results Among the 49 isolates 29 were proved to be plasmid-mediated AmpC β-lactamases-producing strains with incidence rate of 59.18%.In the 29 isolates of plasmid-mediated AmpC β-lactamase-producing strains,the DHA gene was found in 16 isolates,CIT gene in 6 isolates and EBC gene in 7 isolates,and 2 novel genes(ACT-3 and MIR-4)were found in 2 isolates(GenBank accession number:EF125013 and EF587233).Conclusion The incidence rate of plasmid-mediated AmpC β-lactamases in cefoxintin-resistant K.pneu is rather high and 2 novel genes were discovered in Anhui Province.Carbapenems should be the first choice for the infection caused by plasmid-mediated AmpC β-lactamase-producing Klebsiella pneumoniae.