Detection of Genotypes of Plasmid-mediated AmpC β-Lactamase and Analysis of Antimicrobial Resistance of Klebsiella pneumoniae in Harbin

OBJECTIVE To determine the drug resistance phenotype and genotype of plasmid-mediated AmpC β-lactamase in Klebsiella pneumoniae isolated from Harbin.METHODS Isolates of K.pneumoniae with an inhibition ring to cefoxitin of ≤18 mm diameter were used.Antimicrobial susceptibilities were determined by disc diffusion method.AmpC genes were detected by PCR with six pairs of primers.RESULTS Sixty-three isolates had an inhibition ring to cefoxitin of ≤18 mm diameter and 26(11.3%)were detected to be AmpC-producing in a total of 231 clinical isolates of K.pneumoniae.Seventy-six percent,70.2%,53.8%,50.5%,57.7%,38.5% and 7.7% of AmpC-producers were resistant to cefoxitin,cefotaxime,ceftazidime,amoxicillin/clavulanic cid,ciprofloxacin,amikacin and imipenem,respectively.ACT,DHA and CIT types of AmpC beta-lactamase were detected in 13,8 and 5 isolates,respectively.No ACC,MOX and FOX were detected.CONCLUSIONS The AmpC β-lactamase in Harbin is mainly in the types of ACT,DHA and CIT.AmpC-producing K.pneumoniae shows decreased susceptibilities to cefoxitin and third generation cephalosporins.