停乳链球菌污染所致食源性疾病暴发事件的流行病学调查

Epidemiologic investigation of foodborne disease outbreaks caused by Streptococcus dysgalactiae contamination

目的查明成都市2个区聚集性疫情事件发生的原因,快速控制事件发展,防止此类事件的再次发生。方法2020年7月—2021年10月,成都市2个区先后发生3起以发热、咽痛为主要表现的聚集性疫情,通过对工业园区及学校所有相关人员进行排查,开展个案调查和描述流行病学分析,建立病因假设。采用回顾性队列研究及病例对照的方法开展分析流行病学调查。通过访谈、查阅资料、现场勘察等方式对食品安全、环境卫生情况开展调查,进一步找出可能存在危害环节及危险因素。采集患者呼吸道、肠道生物样本及环境样本对呼吸道和肠道常见致病菌进行快速筛检、细菌培养及PCR检测。结果3起事件分别搜索到病例65人(罹患率21.5%)、158人(罹患率29.2%)及93人(罹患率1.0%)。临床表现均以发热、咽痛、乏力为主要表现,偶有腹痛、腹泻、恶心、呕吐及皮疹等其他症状。流行曲线均提示为点源暴露模式,空间无聚集,人群无特殊。3起事件分析流行病学调查结果均提示发病前3 d食堂内部分食品可能为危险因素。食品卫生学调查发现,3起事件发病前均存在没有凉菜加工间但提供凉拌菜的情况,事件B在发病前约1周有食堂切配人员手外伤未调离工作岗位。3起事件均从多名病例咽拭子中检出停乳链球菌,其中事件B食堂从业人员中也检出型别一致的停乳链球菌。结论3起事件均是由停乳链球菌污染导致的食源性疾病暴发事件,动物性食品原材料被污染或者从业人员感染后仍从事食品制作,食堂均提供凉拌菜且制作过程不规范等可能是导致此类事件发生的主要原因。提示今后要高度关注停乳链球菌导致的发热聚集性疫情的食源性疾病风险。

Objective In order to find out the cause of the clustered epidemic events in 2 districts of Chengdu,quickly control the development of the incident and prevent the recurrence of such incidents.Methods From July 2020 to October 2021,three clusters of epidemics with fever and sore throat as the main manifestations occurred successively in two districts of Chengdu City.Through the investigation of all relevant personnel in industrial parks and schools,case investigation and epidemiological analysis were carried out to establish the etiological hypothesis.Retrospective cohort study and case-control were used to carry out the epidemiological investigation.The investigation of food safety and environmental hygiene was carried out through interviews,data reference,field investigation and other ways to further find out possible harmful links and risk factors.Respiratory tract and intestinal biological samples and environmental samples were collected for rapid screening,bacterial culture and PCR detection of common respiratory tract and intestinal pathogens.Results The three incidents identified 65 cases(21.5%prevalence),158 cases(29.2%prevalence)and 93 cases(1.0%prevalence),respectively.The clinical manifestations were mainly fever,sore throat,and malaise,with occasional abdominal pain,diarrhea,nausea,vomiting,and rash.The epidemiologic curves suggested a point-source exposure pattern,with no spatial aggregation and no specific populations affected.Analytical epidemiological investigations suggested that some of the food items in the cafeteria may have been risk factors within three days before the onset of illness.Food hygiene investigations revealed that,prior to the onset of the incidents,coleslaw was provided without a proper cold dish processing area in all three events.Approximately a week before the onset of Incident B,a cafeteria food handler sustained a hand injury but was not reassigned.Streptococcus dysgalactiae was detected in throat swabs of multiple cases in all 3 incidents,and the same strain was detected in cafeteria workers in Incident B.Conclusions All three incidents were foodborne disease outbreaks caused by Streptococcus dysgalactiae contamination.Likely contributing factors include contamination of animal food raw materials,food handlers continuing to work while infected,and non-standard preparation of cold dishes in canteens.It is suggested that the future foodborne disease risk should be highly concerned about the fever aggregation outbreak caused by Streptococcus dysgalactiae.