后疫情时代下市售生鲜猪肉中单增李斯特菌的污染评估

Assessment of Listeria monocytogenes contamination in retail fresh pork in the post-COVID-19 era

【背景】2019年底新型冠状病毒肺炎(corona virus disease 2019,COVID-19)疫情的流行给食品安全带来了挑战。【目的】评估后疫情时代市售生鲜猪肉中单增李斯特菌(Listeria monocytogenes)的污染情况。【方法】选取2020−2021年疫情期间不同地点、不同包装方式、不同季度的生鲜猪肉,分析单增李斯特菌的污染率和污染水平,并对分离菌株的流行病学特征进行分析。【结果】生鲜猪肉中单增李斯特菌的污染率为15.28%(77/504),其中猪肉直营店和农贸市场的污染率高于超市。不同包装方式中,预包装和简易包装的污染率高于散装样品,并且不同季度的污染率存在显著性差异,第三季度污染率最高,为27.78%。定量结果发现,40.26%超过10 MPN/g(MPN:most probable number),其中有3个样品的污染水平超过100 MPN/g。血清型分析结果发现,1/2a-3a(48.05%)和1/2c-3c(44.16%)为主要血清型。耐药性试验结果表明,19.50%的分离株存在多重耐药,有2株(2.60%)对所有抗生素都敏感,68株(88.30%)对苯唑西林耐药,46株(59.70%)对氨苄西林耐药,45株(58.40%)对头孢噻肟耐药。【结论】后疫情时代下不同地点、不同包装方式、不同季度的市售生鲜猪肉中存在不同程度的单增李斯特菌污染,个别产品污染水平较高,血清分布和耐药特征多样,有必要加强食品安全监管,以减少食源性疾病的发生。

[Background]The outbreak of corona virus disease 2019(COVID-19)at the end of 2019 posed a major challenge to food safety.[Objective]To assess the contamination of Listeria monocytogenes in commercial fresh pork in Nanjing in the post-COVID-19 era.[Methods]We collected the fresh pork samples from different locations and in different packages and quarters during 2020−2021,and then analyzed the contamination rate and level of L.monocytogenes and the epidemiological characteristics of the isolates.[Results]The contamination rate of L.monocytogenes in fresh pork was 15.28%(77/504).The contamination rates of pork from open-air market and pork direct-sale stores were higher than that from supermarkets.Among different packaging methods,pre-package and simple package had higher contamination rate than bulk package.Further,the contamination rate varied significantly among different quarters,being the highest(27.78%)in the third quarter.Quantitative results demonstrated that 40.26%of the positive samples had the contamination level exceeding 10 MPN/g(MPN:most probable number).In particular,the contamination level of three samples exceeded 100 MPN/g.The results of serotyping showed that 1/2a-3a(48.05%)and 1/2c-3c(44.16%)were the main serotypes.Moreover,19.50%of the isolates were multi-antibiotic resistant,and 2 isolates(2.60%)were sensitive to all the test antibiotics.Among the 77 isolates,68(88.30%),46(59.70%),and 45(58.40%)were resistant to oxacillin,ampicillin,and cefotaxime,respectively.[Conclusion]In the post-COVID-19 era,the L.monocytogenes contamination of fresh pork varied among different locations,packaging methods,and quarters.A few products had high contamination levels,and the serotype distribution and resistance characteristics were diverse.Therefore,it is essential to strengthen food safety supervision to reduce the occurrence of foodborne diseases.