中国大陆地区肠杆菌科细菌aac（6＇）-Ib—cr基因检出率与常见药物不同耐药水平关系的研究

Comparison Study of aac（6＇）-Ib-cr in Clinical Isolates of Enterobacteriaceae in the Mainland of China

目的研究中国大陆地区质粒介导的耐药基因aac（6’）-Ib—cr在肠杆菌科细菌环丙沙星和阿米卡星敏感株与耐药株中及在ESBL阳性株和阴性株中的分布状况和比较分析.方法从2006年全国美平耐药监测网点中收集241株非重复的大肠埃希菌和肺炎克雷伯菌，用琼脂对倍稀释法测定所有菌株对环丙沙星等药物的MIC值.采用PCR检测所有菌株的aac（6’）-Ib基因;并以内切酶BtsCI酶切消化aac（6’）-Ib的PCR阳性产物和/或DNA测序以确定aac（6’）-Ib—cr.结果在241株筛选出的大肠埃希菌和肺炎克雷伯菌中，环丙沙星的耐药率为61．4%（148/241）;阿米卡星的耐药率为10．0%（24/241）;ESBL阳性株占56．8%（137/241）.aac（6’）-Ib—cr的总阳性率为12．4%（30/241）.经妒检验，aac（6’）-Ib—cr基因在环丙沙星敏感菌株与耐药菌株中的检出率差异具有统计学意义（0．0%和20．3%，X^2=20．655，P〈0．05）;在阿米卡星敏感菌株与耐药菌株中约检出率差异无统计学意义（12．0%和16．7%，X^2=0．112，P〉0．05）;在ESBL阳性株与ESBL阴性株中的检出率差异无统计学意义（16．1%和7．7%，X^2=3．797，P〉0．05）.结论质粒介导喹诺酮类耐药基因aac（6’）-Ib-cr在大肠埃希菌和肺炎克雷伯菌中的分布广泛，而且该基因在环丙沙星敏感菌株与耐药菌株的检出率差异具有统计学意义，而在阿米卡星敏感菌株与耐药菌株中的检出率差异无统计学意义，在ESBL阳性株与阴性株中的检出率亦无统计学意义.

Objective To investigate the prevalence of pasmid-mediated quinolone resistance aac（6＇）-Ib-cr in the clinical isolates of Escherichia coli and Klebsiella pneumoniae in China. Methods All non-repetitive 241 clinical isolates with Escherichia coli and Klebsiella pneumoniae collected from the Chinese Meropenem Susceptibility Surveillance study collection. The MIC of ciprofloxacin and other antibacterial agents were determined by agar dilution. Aac（6＇）-Ib gene were detected by PCR ,aac （6＇）-Ib-cr gene was further identified by the digestion with BtsCI and/or direct sequencing. The isolates were divided into two groups according to the resistence level of ciprofloxacin or amikacin and ESBLs. Results In 241 screen Escherichia coli and Klebsiella pneumoniae, resistance of ciprofloxacin was 61.4 % （148/241 ） ; resistance of amikaein was 10. 0%（24/241）;producing ESBLs accounts for 56.8%（137/241）. Aac（6＇）-Ib-cr was present in 12.4%（30/241） of isolates. There was significant difference between the two groups （the Susceptibility and resistance for ciprofloxacin） in the prevalence of isolates carrying the aac （6＇）-Ib-cr genes （0.0 % and 20.3 %,X^2= 20. 655 ,P〈0.05）. There was no significant difference between the two groups （the Susceptibility and resistance for amikacin） in the prevalence of isolates carrying the aac （6＇）-Ib-cr genes （12. 0% and 16. 7 %, X^2= 0. 112, P 〉 0. 05）. There was no significant difference between the two groups（producing ESBLs and non-producing ESBLs） in the prevalence of isolates carrying the aac （6＇）-Ib-cr genes （16. 1% and 7.7% ,X^2=3. 797,P〉0. 05）. Conclusion The plasmid-mediated aac（6＇ ）-Ib-cr widely existed in the Escherichia coli and Klebsiella pneumoniae strains in China. And there is significant difference between the two groups （the Susceptibility and resistance for ciprofloxacin） in the prevalence of isolates carrying the aac（6＇ ）-Ib-cr genes, and there is no significant difference between the two groups （the Susceptibility and resistance for amikacin,as well as producing ESBLs and non-producing ESBLs）in the prevalence of isolates carrying the aac（6＇ ）-Ib-cr genes.