急性腹泻患者肠道细菌中多黏菌素耐药基因mcr的调查分析

Investigation of colistin resistance gene mcr in gut bacteria from patients with acute diarrheal

目的调查并分析急性腹泻患者肠道细菌中多黏菌素耐药基因mcr的携带情况。方法收集河南省人民医院肠道门诊150例急性腹泻患者的新鲜粪便样本，肉汤富集增菌后直接PCR筛查多黏菌素耐药基因mcr；分离培养耐多黏菌素菌株；Bruker Biotyper质谱仪鉴定菌种；微量肉汤稀释法对菌株进行常见抗生素敏感性试验；特异性PCR和测序分析检测包括mcr耐药基因在内的常见耐药基因。结果150例急性腹泻患者粪便中，有4例检出mcr-1型多黏菌素耐药基因，阳性率2．7％；其中1例粪便中同时检测到mcr-3，阳性率为0．7％。分离培养后获得4株大肠埃希菌和1株维氏气单胞菌；特异性PCR和测序证实4株大肠埃希菌均携带mcr-1基因，维氏气单胞菌携带mcr-3基因。结论本次调查中发现门诊急性腹泻患者粪便中多黏菌素耐药基因主要是mcr-1；在临床上也存在mcr-3耐药基因；发现mcr-1和mcr-3多黏菌素耐药基因共存于同一患者肠道中，提示潜在的传播风险，值得引起高度关注。

Objective To investigate the presence of colistin resistance gene mcr in gut bacteria from patients with acute diarrhea. Methods Fresh stool samples were collected from 150 outpatients with acute diarrhea in the intestinal clinic of Henan Provincial People＇s Hospital, and were directly detected for the presence of mcr by PCR after enrichment in the broth. The mcr-producing bacteria were further isolated and identified by MALDI-TOF MS （ Bruker Biotyper） . Antimicrobial susceptibility of these isolates was conducted by micro-broth dilution method. The presence of other antimicrobial genes were investigated by PCR and sequencing. Results Among the 150 cases of acute diarrhea, 4 patients （2.7%） were positive for mcr-1 gene, and only 1 （0. 7% ） contained both mcr-1 and mcr-3. Four isolates of Escherichia coli and one isolate of Aeromonas veronii were obtained from the met positive cases. The presence of mcr-1 gene was found in all of the E. coli isolates, and the mcr-3 gene was identified in A. veronii. Conclusions Our study demonstrated the relatively low prevalence of colistin resistant gene in the faeces of acute diarrhea outpatients, and mer-1 is the dominant colistin resistant gene. The presence of mcr-3 gene was also found in the clinical sample, and it indicats the coexistence of mcr-1 and mcr-3 in the intestinal tract of diarrhea patient. We should pay attention to the potential transmission of these resistance genes and further investigations are urgently needed.