摘要
【目的】研究质粒介导喹诺酮类药物耐药基因qnrS在一养殖场中的流行特点。【方法】分离养殖场不同来源样品中的大肠杆菌菌株,利用美国临床标准委员会(CLSI)推荐的药敏纸片法测定菌株耐药情况,通过质粒接合试验获得qnrS阳性接合子,测定qnrS对喹诺酮类药物最小抑菌浓度(MIC)值的影响及其与其它类抗生素耐药性的相关性,利用脉冲场凝胶电泳分析该场中qnrS阳性菌株遗传进化关系。【结果】环境源菌株qnrS的阳性率为29.2%,显著高于禽源菌株基因检出率(13.4%),新进的雏鸡可迅速从养殖场中获得qnrS基因并在鸡群中流行。qnrS基因可使接合子对喹诺酮类药物MIC值不同程度升高,并且与其它五类抗生素具有相关性,不同qnrS阳性菌株间遗传关系较远,但也存在同一克隆株的流行。【讨论】qnrS基因主要通过质粒的播散等进行水平传播,同时也存在同一克隆株的流行传播。qnrS基因多样性及其水平传播方式造成了它的广泛流行,加强对耐药基因的监测及研究对减少多重耐药菌株的产生具有重要意义。
[ Objective] To investigate the prevalence and transmission of plasmid-mediated quinolone resistance qnrS gene among Escherichia coli isolates in a poultry farm and its environment. [ Methods] E. coli isolates from fecal samples in a poultry farm and its environment from February to June 2010 were screened for the prevalence and dynamic changes of qnrS gene. Susceptibility testing, conjugant experiments, and pulsed field gel electrophoresis of qnrS-positive isolates were also performed. [ Results] A total of 379 isolates were randomly obtained from feces samples of chickens, ducks and geese in a poultry farm and its environment. The qnrS positive strains were detected in all sources of isolates and two alleles of qnrS were prevalent on this farm. The positive rate of qnrS gene in environmental strains was 29.2% , which was significantly higher than that in the avian strains （13.4%）. Chicken can quickly acquire qnrS gene after they live on this farm. Transconjugants of the qnrS gene can elevate ciprofloxacin Minimun inhibitory concentrations （MICs） by 16- 32 fold compared with the recipient. Various determinants for resistance to other antimicrobial agents were also transferred with the qnrS plasmid. The Xba I PFGE analysis of the qnrS positive strains showed that the dissemination of qnrS was not mainly due to the clonal dissemination of positive strains. However, qnrS-positive strains with indistinguishable PFGE patterns were found in ducks and environment. [ Conclusion] Both horizontal gene transfer and clonal spread could be responsible for the dissemination of the qnrS gene in the poultry farm and its environment, but it is mainly disseminated by horizontal transmission.
出处
《微生物学报》
CAS
CSCD
北大核心
2013年第10期1080-1086,共7页
Acta Microbiologica Sinica
基金
国家自然科学基金(31001079)
国家"863计划"(2012AA101601-6)
江苏高校优势学科建设工程项目~~
关键词
质粒介导喹诺酮类药物耐药
qnrS
最小抑菌浓度
多重耐药
脉冲场凝胶电泳
plasmid-mediated quinolone resistance, qnrS, minimum inhibitory concentration, multiple drug resistance,pulsed field gel electrophoresis
