头孢西丁耐药肺炎克雷伯菌AmpC基因和ESBLs检测及耐药性分析

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

目的了解深圳地区头孢西丁耐药肺炎克雷伯菌头孢菌素酶(AmpC酶)基因型分布、产超广谱β-内酰胺酶(ESBLs)的情况及其耐药特点。方法收集深圳地区三家大型综合医院临床标本分离对头孢西丁耐药的肺炎克雷伯菌73株。用碱裂解法提取菌株的质粒,采用多重PCR扩增AmpC基因,应用DNA测序确定其基因型。并对所有菌株进行ESBLs表型确证试验;用K-B法对其进行药物敏感试验。结果 48株(65.8%)AmpC基因扩增阳性,经DNA测序显示,其中46株为DHA-1型,1株为CMY-2型,1株同时产DHA-1和CMY-2型;73株肺炎克雷伯菌中49株ESBLs阳性,其中36株AmpC基因和ESBLs均为阳性。AmpC和(或)ESBLs阳性菌株对多数药物的耐药率高于AmpC和ESBLs均阴性者。结论本地区头孢西丁耐药肺炎克雷伯菌质粒AmpC酶检出率高,基因型主要为DHA-1,同时产AmpC酶和ESBLs菌株较常见。

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.