Detection for AmpC genes and ESBLs of cefoxitin-resistant Klebsiella pneumoniae and analysis of its antibiotic resistance.

Objective To understand the genotype distribution of AmpC β-lactamases and occurrence of extended spectrum β-lactamases(ESBLs) in cefoxitin-resistant Klebsiella pneumoniae isolates in Shenzhen area.Method 73 cefoxitin-resistant Klebsiella pneumoniae isolates from three large general hospitals in Shenzhen area were analyzed.The plasmids of the strains were extracted,and the AmpC genes were detected by using multiplex PCR.DNA sequencing was carried out for AmpC genotyping.The antibiotic resistance of the isolates was determined by the Kirby-Bauer methods.Result 48(65.8%) strains were detected as AmpC gene positive.The DNA sequencing revealed that 46 of them were DHA-1 type,one was CMY-2 type,while the other one was both DHA-1 and CMY-2 type;49 of the 73 Klebsiella pneumoniae strains were detected as ESBLs-producing strains,36 of which were AmpC-positive.The AmpC-and/or ESBLs-positive strains showed higher resistance to most antibiotics than those without any AmpC or ESBLs.Conclusion The detection rate of plasmid mediated AmpC β-lactamases is high for cefoxitin-resistant Klebsiella pneumoniae isolates in Shenzhen region,with the main genotype being DHA-1.The isolates which simultaneously producing AmpC enzymes and ESBLs are common.