一起疑似食物中毒暴发事件的病原学分析

  目的  阐明一起疑似由蜡样芽胞杆菌污染奶源引起的食物中毒暴发事件的病原学特征，为查明暴发源头和临床治疗提供依据。  方法  对198例患儿进行流行病学调查，采集可疑奶制品和病例标本，进行菌株分离和鉴定。 分离到的蜡样芽胞杆菌菌株进行脉冲场凝胶电泳（PFGE）分子分型、全基因组测序以及毒力基因分析。 采用微量肉汤稀释法进行药物敏感性测定。  结果  流行病学调查显示198例患儿均有不同程度的腹痛、腹泻和发热等症状，符合食源性疾病暴发定义。 共分离到25株蜡样芽胞杆菌（5株来自奶制品，20株分离自病例标本）。 PFGE分型分析显示，13株病例标本菌株与5株奶源性菌株条带具有高度相似性。 25株蜡样芽胞杆菌对环丙沙星、万古霉素、四环素、氯霉素、庆大霉素和亚胺培南均敏感，但对氨苄西林、青霉素完全耐药。  结论  该起食物中毒暴发事件疑似由蜡样芽胞杆菌污染引起，应加大食品安全知识的宣传普及，提高食品安全意识，预防类似事件的发生。

Etiological analysis on an outbreak of suspected food poisoning

  Objective  To understand the etiological characteristics of an outbreak of food poisoning suspected to be caused by Bacillus cereus contaminated milk, and provide theoretical basis for food poisoning source identification and clinical treatment.   Methods  An epidemiological investigation was carried out in 198 cases, and suspected dairy product samples and case samples were collected for pathogen isolation. The isolates of Bacillus cereus were molecularly classified by pulsed field gel electrophoresis (PFGE). The whole genome sequencing (WGS) was carried out and the virulence genes were analyzed. Micro broth dilution method was used for the drug susceptibility test of the isolates.   Results  The epidemiological investigation indicated that all the 198 cases showed abdominal pain, diarrhea, and fever at different degree, which met the definition of foodborne disease outbreak. A total of 25 strains of B. cereus were isolated, in which 5 were isolated from dairy products, and 20 were isolated from case samples. PFGE analysis showed that there was a high similarity between 13 strains from cases samples and 5 strains from dairy product samples. The drug susceptibility test showed that the 25 B. cereus stains were sensitive to ciprofloxacin, vancomycin, tetracycline, chloramphenicol, gentamicin and imipenem, but completely resistant to ampicillin and penicillin.   Conclusion  The outbreak of food poisoning was caused by B. cereus contamination. It is necessary to strengthen the health education about food safety to prevent the outbreaks of food borne diseases.