农贸市场中蜚蠊携带单增李斯特菌的调查及菌株特征分析

Phenotypic and genotypic characteristics of L. monocytogenes isolates from cockroaches in farm produce market

目的初步探索农贸市场中蜚蠊李斯特菌的携带情况及农贸市场中食品李斯特菌污染的危险因素。方法2015年10-12月从北京市某肉类(猪肉、羊肉、鸡肉)和水产品销售市场共采集147份蜚蠊样本进行李斯特菌的分离鉴定,并对分离到的单增李斯特菌进行血清型(serotyping)、脉冲场凝胶电泳(PFGE)分型以及多位点序列分型(MLST)分析。结果蜚蠊样本中李斯特菌的分离率为58.06%(78/147),包括单增李斯特菌、英诺克李斯特菌、威尔李斯特菌,其中,单增李斯特菌的分离率为17.68%(26/147),以水产品销售区域蜚蠊中分离率最高(18.18%)。血清型分析将26株单增李斯特菌分为4种血清型,分别为1/2c、1/2a、3a和1/2b,优势的血清型为1/b(34.60%)和1/2c(34.60%);PFGE分析将26株单增李斯特菌分为11种PFGE带型,优势的PT型为PT16(19.23%)和PT30(19.23%)。MLST分析将26株单增李斯特菌分为5种序列型,分别为ST87、ST9、ST121、ST155、ST35,优势的序列型为ST87(34.62%)。结论农贸市场中蜚蠊能携带李斯特菌且不同食品销售市场中蜚蠊所携带的单增李斯特菌的分子型别不同,可能与不同食品类型携带的单增李斯特菌的型别不同而蜚蠊与食品间有交叉污染有关,因此蜚蠊可能成为农贸市场中传播单增李斯特菌并污染食品的危险因素之一。

Objective To understand the carriage of Listeria monocytogenes by cockroaches and whether cockroach is a risk factor for L. monocytogenes caused food contamination in farm produce markets. Methods A survey was conducted in a farm produce market in Beijing from October to December 2015. A total of 147 cockroach samples were collected from the farm produce market selling raw pork, raw mutton, raw chicken meat and aquatic product. The L. monocytogenes isolates were analyzed by serotyping, multi locus sequence typing （MLST） and pulsed-field gel electrophoresis （PFGE）. Results The positive rate of Listeria in cockroaches, including L. monocytogenes, L. innocua and L. welshimeri, was 58. 06% （78/147）, and the positive rate of L. monocytogenes was 17.68% （26/147）. The detection rate of L. monocytogenes was highest in aquatic product section （ 18. 18% ）. Serotyping divided 26 isolates into four serotypes, i.e. 1/2c, 1/2a, 3a and 1/2b. Serotype 1/b （34. 6% ） and 1/2c （34. 60% ） were predominant. By PFGE, the 26 isolates were classified into 11 PFGE types （PTs）, PT16 （19. 23% ） and PT30 （19, 23% ） were the major types. By MLST, 5 sequence types （STs） were found （ ST87, ST9, ST121, ST155 and ST35） and the major ST was ST87 （34. 62% ）. Conclusion Cockroaches in farm produce markets can carry L. monocytogenes and the genotypic and phenotypic characteristics L. monocytogenes varied with the cockroaches fdifferent sources, which might be due to the different L. monocytogenes in different foods and co- contamination between cockroach and food. Cockroaches is a risk factor for L. monocytogenes spread and contamination in farm produce markets.