北京某区一起疑似金黄色葡萄球菌肠毒素中毒分析

Analysis of a suspected Staphylococcus aureus enterotoxin poisoning in a district of Beijing

目的 通过实验室检测及全基因组测序,分析一起金黄色葡萄球菌肠毒素(SEs)中毒,为应对此类食源性暴发事件提供经验。方法 采集可疑受污染食品、病例肛拭子和环境涂抹样本,采用金黄色葡萄球菌5种肠毒素(SEA、SEB、SEC、SED、SEE)的酶联免疫吸附实验(ELISA)检测及肠毒素基因(sea、seb、sec、sed、see)荧光PCR方法检测;对分离株进行耐药表型检测和全基因组测序并构建进化树。结果 3件可疑受污染的食品未检出SEs。荧光PCR检测3件可疑污染食品的增菌液结果都为nuc+/seb+。从3件可疑受污染食品中共分离到9株seb+金黄色葡萄球菌,其中从食品1中分离到2株t78型和1株t437型,食品2和食品3中分离到的菌株均为t437型,同一spa分型菌株具有相同耐药表型。从1件环境涂抹中分离出2株5种肠毒素基因均为阴性的金黄色葡萄球菌,均为t571型。由9株食品分离株和2株环境分离株构建cgSNP进化树,显示形成3个独立且遗传关系较远分支。9株食品分离株产毒培养后ELISA肠毒素检测结果为SEB阳性。结论 本起事件为可疑SEB中毒事件,全基因组测序可提供较为全面的生物信息数据以应对此类事件。

Objective To provide experience for the response to Staphylococcus aureus enterotoxin(SEs)poisoning outbreak,lab test and whole genome sequencing(WGS)technology was used to analyze a SEs poisoning outbreak.Methods Suspected contaminated food,anal swabs and environmental smear samples in this event was collected.enzyme-linked immunosorbent assay(ELISA)for five SEs(SEA,SEB,SEC,SED,SEE),and real time PCR for genes of SEs(sea,seb,sec,sed,see)were performed.Drug resistance phenotype and WGS were performed in Staphylococcus aureus strains isolated from samples,and a cgSNP evolutionary tree was constructed.Results SEs were negative for three suspected contaminated foods.Real time PCR for enrichment solution of the three suspected contaminated foods were all nuc+/seb+,and 9 isolates of seb+S.aureus were isolated from three suspicious contaminated foods,among which two isolates of type t78 and one isolate of type t437 from food 1,and the isolates from food 2 and food 3 were all type t437,with the same spa typing isolates having the same drug-resistant phenotype.Two isolates of S.aureus were isolated from one environmental smear,which negative for five SEs genes and presenting the same type t571.Three independent and genetically distant branches were formed in a cgSNP evolutionary tree constructed based on nine food isolates and two environmental isolates of S.aureus.Nine food isolates were positive for SEB by ELISA.Conclusion This incident is a suspected SEB intoxication,and whole genome sequencing may provide more comprehensive bioinformatic data to respond to such incidents.