一起由产气荚膜梭菌和肠聚集性大肠埃希菌共感染导致的聚集性腹泻事件病原学分析

Pathogenic analysis of a cluster diarrhea event caused by co-infection with Clostridium Perfringens and enteroaggregative Escherichia coli

目的对一起产气荚膜梭菌和肠聚集性大肠埃希菌(PFGE)混合感染导致的腹泻暴发事件进行病原学分析。方法采集暴发事件的病例粪便样本;病原体筛查使用实时荧光PCR方法;细菌分离使用培养法;菌株毒力基因鉴定使用普通PCR方法;菌株抗生素敏感性测试使用微量肉汤稀释法,菌株分子分型使用脉冲场凝胶电泳方法。结果9份粪便样本核酸中,6份肠聚集性大肠埃希菌astA+(+:基因阳性),8份样本产气荚膜梭菌cpa+,5份样本同时检出2种病原体。6份粪便标本分离到肠聚集性大肠埃希菌,均astA+;8份粪便标本分离到产气荚膜梭菌,其中2株cpa+/cpe+,6株cpa+/β2+。6株肠聚集大肠埃希菌分为2种PFGE带型,其中5株同带型,也为同种耐药表型(AMP-CFZ);8株产气荚膜梭菌分为3种PFGE带型,其中6株cpa+/β2+的菌株同带型。结论本次腹泻暴发事件可能由2种病原体混合感染导致。

To analyze the etiological characteristics of an outbreak of diarrhea caused by a mixed infection with Clostridium perfringens and enteroaggregative Escherichia coli,we collected stool samples from cases in the outbreak.We then performed pathogen screening with quantitative Real-time PCR.Afterward,we used a culture method to isolate bacteria,and we used PCR to identify virulence genes.We used broth microdilution to test the antibiotic sensitivity of the strains.Pulsed field gel electrophoresis(PFGE)was used for molecular typing.Among the nine fecal samples,six were enteroaggregative Escherichia coli astA+(+:Gene positive),eight were Clostridium perfringens cpa+,and five were positive for two pathogens.We isolated enteroaggregative Escherichia coli from six fecal specimens,all of which were astA+,and Clostridium perfringens from eight fecal specimens:two cpa+/cpe+and six cpa+/β2+.Six strains of enteroaggregative Escherichia coli were divided into two PFGE bands,five of which showed the same band type and the same drug resistance phenotype(AMP-CFZ).Eight strains of Clostridium perfringens were divided into three PFGE bands;six strains of cpa+/β2+had the same band type.The outbreak of diarrhea might have been caused by a mixture of the two pathogens.