苏州市食品中单增李斯特菌污染状况及分子特征分析

目的研究2016—2020年苏州市各类食品中单增李斯特菌的污染状况及分子特征。方法将采样食品按WS/T464—2015《食物成分数据表达规范》进行分类,计算各类食品污染率,通过聚合酶链式反应(polymerase chain reaction,PCR)和凝胶电泳对毒力基因(inlA、inlB)和耐药相关基因(virR、dltA、dltB、dltC、dltD、mprF)进行检测,通过脉冲场凝胶电泳进行分子分型。结果683件食品中共检出44件阳性样品,总体检出率6.4%。各类食品中以肉类食品的检出率最高(17.2%),肉类食品中以预制肉制品检出率最高(37.2%)。分离的44株单增李斯特菌毒力基因inlA携带率为100.0%,inlB携带率为97.7%,耐药相关基因virR、dltA、dltB、dltC、dltD、mprF的携带率分别为90.9%、100.0%、90.9%、100.0%、95.5%、97.7%。分离株的PFGE型别可分为11个基因型簇,相似度为53.3%~100.0%,有11组100.0%相似度的带型,其中有3组为同一时间,同一地点采集样品所分离菌株。结论苏州市肉类食品特别是预制肉制品单增李斯特菌污染较为严重,而且污染菌株毒力基因和耐药相关基因总体携带率高。PFGE的11种带型中B和E为优势带型,占比40.9%。零售环节存在样品交叉污染单增李斯特菌的风险。

Analysis of contamination status and molecular characteristics of Listeria monocytogenes in food in Suzhou City

Objective To study the contamination status and molecular characteristics of Listeria monocytogenes in various foods in Suzhou City from 2016 to 2020.Methods The food samples were classified according to WS/T 464—2015 Regulation of food composition data expression,and the contamination rates of all kinds of food were calculated.Virulence genes(inlA,inlB)and drug-resistance related genes(virR,dlt A,dltB,dltC,dltD,mpr F)were detected by polymerase chain reaction(PCR)and gel electrophoresis.Molecular typings were performed by pulsed-field gel electrophoresis.Results A total of 44 positive samples were detected out of 683 food samples,with an overall positive rate of 6.4%.Among all kinds of foods,the detection rate of meat was the highest(17.2%),and among the meat foods,the detection rate of pre-made meat products was the highest(37.2%).The isolated 44 Listeria monocytogenes strains of virulence gene inlA carrying rates were 100.0%,and inlB carrying rates were 97.7%.The carrying rates of drug-resistance related genes virR,dlt A,dltB,dltC,dltD and mpr F were 90.9%,100.0%,90.9%,100.0%,95.5%and 97.7%,respectively.The PFGE types of the isolates could be divided into 11 genotype clusters with a similarity of 53.3%~100.0%.There were 11 groups of 100.0%similar band patterns,of which 3 groups were strains isolated from samples collected at the same time and place.Conclusion The contamination of Listeria monocytogenes in meat products,especially pre-made meat products,is serious in Suzhou City,and the overall carrying rates of virulence genes and drug-resistance genes of the strains are high.Among the 11 kinds of PFGE band types,B and E are the dominant band types,accounting for 40.9%.There is a risk of cross-contamination between samples with Listeria monocytogenes in the retail sector.