污水厂产超广谱β内酰胺酶大肠杆菌通过接合水平传递耐药性

【目的】研究废水中产超广谱β-内酰胺酶大肠杆菌中可移动质粒在耐药基因水平传播机制中的作用。【方法】对污水厂分离所得的50株产ESBLs大肠杆菌进行接合试验,并对所得的接合子采用纸片扩散法测定其对15种常见药物的耐药表型,针对质粒介导的产ESBLs菌株的耐药基因设计7对特异性引物对接合子进行PCR扩增。【结果】研究结果显示,80份水样分离得50株产ESBLs大肠杆菌,共接合成功35株细菌,接合成功率高达70%。接合子与供体菌相比,均发生耐药谱型的改变,且存在丢失一种或几种药物耐药性且产生另一种或几种药物耐药性的现象。PCR扩增结果显示,接合子与供体菌相比,耐药基因型有所减少或不变,bla_(TEM)、bla_(CTX-M)基因全部接合成功,bla_(SHV)基因仅1株未接合成功,耐氟喹诺酮类基因未发生转移。【结论】本研究表明,不同的耐药基因可能位于不同的可移动质粒上,可移动质粒在大肠杆菌耐药性水平传播的过程中起到了十分重要的作用。

Transfer of antimicrobial resistant genes of ESBL-producing Escherichia coli recovered from a wastewater treatment plant

Objective] We explored the role of mobile plasmids in transferring antimicrobial resistant genes in extended-spectrum beta-lactamases (ESBLs)-producing Escherichia coli from a wastewater treatment plant. Methods] Based on the conjugation experiments of ESBL-producing E. coli collected from wastewater, the disk diffusion assay and polymerase chain reaction (PCR) were used to determine the transfer of antimicrobial resistance. Results] A total of 50 ESBL-producing E. coli were collected from 80 water samples (50/80, 62.5%), and successful conjugations were detected among 35 isolates (35/70, 70.0%). The results of PCR further showed that bla_CTX-M and bla_TEM genes were all capable of conjugation transfer, but the horizontal transfer of bla_SHV gene was only detected in one isolate and resistance gene encoding fluoroquinolone was not capable of conjugation transfer in this study. Conclusions] Plasmids carrying different antimicrobial resistant genes may exhibit different capacity of horizontal transfer. Importantly, the mobile plasmids played a very important role in the horizontal transfer of antimicrobial resistance genes of ESBL-producing E. coli.