学校餐饮食品中微生物污染状况及致病菌毒力基因分析

Analysis of microbial contamination status and virulence genes of pathogen bacterium in school catering food

目的掌握学校餐饮及其周边餐饮食品中微生物的污染情况及其携带的毒力基因特征,为食源性疾病的防治提供科学指导。方法2021年5月—2022年10月采集学生食品,按照《食品安全国家标准食品微生物学检验》(GB 4789.4—2016)方法进行单核细胞增生李斯特菌、副溶血性弧菌、金黄色葡萄球菌、蜡样芽胞杆菌、沙门菌、肠集聚性大肠埃希菌的分离鉴定。采用PCR的方法对检测出的56株蜡样芽胞杆菌进行12种毒力基因的检测。采用占比对分类变量进行描述,采用χ^(2)检验进行致病菌检出率的比较。结果食源性致病菌的阳性检出率为17.62%,其中蜡样芽胞杆菌阳性样本56份、金黄色葡萄球菌阳性样本5份、肠集聚性大肠埃希菌阳性样本2份、单核细胞增生李斯特菌阳性样本2份。采集的凉拌菜、盒饭、熟制米面制品中均检出食源性致病菌。不同种类食品样本中致病菌的检出率差异有统计学意义(χ^(2)=17.946,P=0.003)。检测的56株蜡样芽胞杆菌中毒力基因携带率为100.00%,90.00%的菌株同时携带2种以上毒力基因,nheB基因携带率最高为58.93%,其次为nheC基因和cytK基因的32.14%和26.79%。结论学生午餐及学校周边餐饮食品中存在微生物污染情况,且蜡样芽胞杆菌毒力基因携带率高,存在引发食源性疾病风险,应加大监管力度。

Objective To grasp the contamination of microorganisms in school catering and surrounding catering foods and the features of virulence genes they carry,to provide scientific guidance for the prevention and control of foodborne diseases.Methods From May 2021 to October 2022,student food was collected.The isolation and identification of Listeria monocytogenes,Vibrio parahaemolyticus,Staphylococcus aureus,Bacillus cereus,Salmonella,and enteroaggregative Escherichia coli were carried out by the method of the National Standard for Food Safety Microbiological Examination of Food(GB 4789.4-2016).PCR method was used to detect 12 virulence genes of 56 strains of Bacillus cereus detected.Proportion was used to describe classification variables,and the Chi-square test was used to compare the detection rate of pathogenic bacteria.Results The positive detection rate of foodborne pathogenic bacterium was 17.62%,including 56 positive samples for Bacillus cereus,5 positive samples for Staphylococcus aureus,2 positive samples for enteroaggregative Escherichia coli,and 2 positive samples for Listeria monocytogenes.Foodborne pathogen bacterium were detected in cold dishes,boxed meals,and cooked rice and flour products.There was a statistically significant difference in the detection rate of pathogenic bacterium in different kinds of food samples(χ^(2)=17.946,P=0.003).The carrying rate of virulence genes of 56 strains of Bacillus cereus was 100.00%,and 90.00%of the strains carried more than two virulence genes at the same time.Among them,the highest carrying rate of the nheB gene was 58.93%,followed by 32.14%and 26.79%of the nheC gene and the cytK gene.Conclusion There is microbial contamination in students′lunches and catering food around schools,and the high carrying rate of Bacillus cereus virulence gene poses the risk of causing foodborne diseases and supervision should be strengthened.