一起鼠伤寒沙门菌单相变异株引起的食源性疾病事件病原学分析

Pathogen Analysis of a Food-Borne Disease Event Caused by Salmonella typhimurium Monophasic Variant

目的:对一起食源性疾病事件进行溯源调查和病原学分析。方法:结合流行病学调查结果共采集24份可疑食品及器具涂抹样本和17份患者粪便样本。对粪便样本采用Realtime PCR方法筛查病原,并开展流调样本的分离培养。对分离株进行血清学鉴定、PFGE分子分型、药敏试验和全基因组测序,根据全基因组测序数据预测分离株血清型、ST型别、耐药基因及毒力基因携带情况。结果:Realtime PCR结果提示粪便样本沙门菌基因检测阳性,流调样本分离培养得到7株沙门菌,均来源于患者粪便,经多种血清分型试验证实为鼠伤寒沙门菌单相变异株I4,[5],12:i:-。PFGE分子分型试验显示7株沙门菌带型完全一致。基于WGS测序数据预测引起该事件的致病菌为ST34型鼠伤寒沙门菌单相变异株;该分离株对氨苄西林、四环素、链霉素、多西环素及米诺环素耐药,携带aac(6’)-Iaa、aph(6)-Id、aph(3’’)-Ib、blaTEM-1B、sul2及tet(B)6个耐药基因;共注释110个毒力基因,其中101个毒力基因与沙门菌属致病阶段中的附着、侵袭和巨噬细胞内存活相关,未比对出与系统传播有关毒力基因。结论:本次食源性疾病事件是由鼠伤寒沙门菌单相变异株I4,[5],12:i:-感染引起,全基因组测序技术为食源性疾病事件的处理提供了更多的病原学信息。

Objective:To investigate the source of a food-borne disease and analyze its etiology.Method:A total of 24 smeared samples of suspicious food and utensils,17 stool samples were collected.Realtime PCR was used to screen the pathogens in stool samples,and isolation and culture of flow cytometry samples were carried out.Serological identification of the isolates,PFGE molecular typing,susceptibility testing and whole genome sequencing,the whole genome sequencing data were used to predict serotypes,ST types,resistance genes and virulence genes of the isolates.Result:The results of Realtime PCR indicated that the gene of salmonella was positive in fecal samples,and 7 strains of salmonella were isolated from flow sample,all of which came from patients’feces.By a variety of serotyping tests,it was confirmed to be a Salmonella typhimurium Monophasic Variant strain I4,[5],12:I:-.PFGE molecular typing test showed that 7 strains of salmonella had the same pattern.Based on WGS sequencing data,a single-phase variant of ST34 Salmonella typhimurium Monophasic Variant strain.resistant to ampicillin,tetracycline,streptomycin,doxycycline and Minocycline was identified.The isolate was resistant to ampicillin,tetracycline,streptomycin,doxycycline and minocycline.It carried six resistant genes,aac(6’)-Iaa、aph(6)-Id、aph(3’’)-Ib、blaTEM-1B、sul2 and tet(B);A total of 110 virulence genes were annotated,of which 101 were associated with attachment,invasion and macrophage survival in the pathogenic stage of salmonella.No v irulence genes related to systemic transmission were identified.Conclusion:This food-borne disease event was caused by a Salmonella typhimurium Monophasic Variant strain I4,[5],12:I:-infection,and whole genome sequencing technology provides additional information on the etiology of food-borne disease even ts.