肠杆菌科细菌质粒介导喹诺酮类耐药基因的检测

Detection of plasmid-mediated quionlone resistance gene in Enterobacteriaceae

目的调查肠杆菌科细菌中质粒介导喹诺酮类耐药基因(PMQR基因)的现状、基因型以及PMQR基因阳性菌株携带Ⅰ类整合子的情况及其相关性。方法 PCR法对125株肠杆菌科细菌(80株大肠埃希菌、18株肺炎克雷伯菌和27株阴沟肠杆菌)进行PMQR基因和Ⅰ类整合子检测。对阳性扩增产物进行测序分析并对阳性菌株做接合试验,采用琼脂倍比稀释法测定供体菌、受体菌和接合子对喹诺酮类和其他抗菌药物的MIC。结果 125株肠杆菌科细菌检出16株(12.8%)qnr基因阳性,其中8株携带qnrS1基因,8株携带qnrB6基因;另检出15株(12.0%)携带aac(6′)-Ib-cr基因。20株PMQR基因阳性菌株携带Ⅰ类整合子。26株PMQR基因阳性的菌株中有12株接合成功,典型Ⅰ类整合子阳性的菌株中有7株接合成功。与受体菌相比,喹诺酮类等抗菌药物对接合子的MIC值均有不同程度的提高。结论肠杆菌科细菌中存在PMQR基因的流行,PMQR阳性菌株可同时携带整合子基因,这些耐药基因均具有水平转移的特性,故应引起高度重视。

Objective To explore the distribution and genotypes of plasmid-mediated quionlone resistance （PMQR） genes and intI1 integrase genes in Enterobacteriaceae isolates. Methods The PMQR genes and intI1 integrase genes were identified by polymerase chain reaction in the nondupiicate strains of E. coli （80）, E. cLoacae （lg） and K. pneunoniae （27）. The positive PCR products were subject to DNA sequencing analysis. The gene-positive strains were tested by conjugation experiment. The minimum inhibitory concentrations （MICs） of donor, recipient strains and transconjugants were tested by agar dilution method with quinolones and other antimicrobial agents. Results Sixteen （12.8%） of the 125 Enterobacteriaceae isolates were qnr gene positive, including 8 qnrSl positive and 8 qnrB6 positive. Furthermore, the aac（6＇）-Ib-cr gene was identified in 15 （12.0%） strains. Twenty PMQR-positive isolates harbored intI1 integrase gene. The conjugation experiments were successful in 12 of the 26 PMQR-positive isolates and 7 of the 20 intll-positive isolates. The MICs of quinolones and other antimicrobial agents against the transconjugants were higher than the MIC values against recipient strains. Conclusions The PMQR genes are prevalent in Enterobacteriaceae isolates. The PMQR positive isolates can co-harbor integrase genes. These resistance genes have the feature of horizontal transfer, to which close attention should be paid.