Tropical Disease Investigation Center (CIET) and Food Microbiology Research and Training Laboratory (LIMA), Department of Microbiology and Immunology, Faculty of Microbiology, University of Costa Rica, San José 11501, Costa Rica.
J Food Prot. 2021 Oct 1;84(10):1729-1740. doi: 10.4315/JFP-21-020.
Listeria monocytogenes is a pathogenic bacterium associated with ready-to-eat (RTE) meat products sold at the retail level. The objective of this research was to determine the prevalence of L. monocytogenes in RTE meat products sold at retail in Costa Rica and to study the factors associated with the levels of contamination; analyzed factors include hygienic practices within stores (cutting techniques and microbial contamination of products) and the behavior of the isolates (persistence against antimicrobials and transfer potential). A total of 190 samples of RTE meat products were collected and analyzed for the presence of coliforms and Listeria spp. Isolates of L. monocytogenes were then evaluated in terms of resistance to disinfectants (quaternary ammonium compound [QAC] and chlorine) and their transfer potential from food contact surfaces (knife and cutting boards). Overall Listeria spp. prevalence was 37.4% (71 of 190); Listeria innocua was present in 32.1% (61 of 190) of the products, and L. monocytogenes was found in just 2.6% (5 of 190) of the samples. Most contaminated samples were cut with a knife at the moment of purchase (44.2%). When analyzing practices within the stores, it was observed that L. monocytogenes transfer from inoculated knife to salchichón was higher for samples cut at the beginning of the experiment. In addition, L. monocytogenes transfer from inoculated cutting boards was independent of the number of slices but contamination from plastic was higher than wood. Regarding L. monocytogenes resistance to disinfectants, average reductions of 2.6 ± 1.1 log CFU/mL were detected after 6 min of exposure to 200 ppm of chlorine; however, chlorine resistance varied among the strains. Prevalence of L. monocytogenes in RTE meat products sold at retail could be associated with handling practices within the stores; further studies are necessary to estimate the impact of these practices on the overall risk for consumers.
单核细胞增生李斯特菌是一种与零售水平销售的即食（RTE）肉类产品相关的致病菌。本研究的目的是确定哥斯达黎加零售销售的 RTE 肉类产品中单核细胞增生李斯特菌的流行情况，并研究与污染水平相关的因素；分析的因素包括店内卫生实践（切割技术和产品的微生物污染）以及分离株的行为（对抗生素的持久性和转移潜力）。共采集和分析了 190 份 RTE 肉类产品样本，以检测大肠菌群和李斯特菌属的存在。然后，评估了单核细胞增生李斯特菌分离株对消毒剂（季铵化合物[QAC]和氯）的抗性及其从食品接触面（刀和砧板）转移的潜力。总体而言，李斯特菌属的流行率为 37.4%（190 个中的 71 个）；190 个产品中有 32.1%（61 个）存在无害李斯特菌，只有 2.6%（5 个）的样本中发现了单核细胞增生李斯特菌。受污染最严重的样本是在购买时用刀切割的（44.2%）。在分析店内的操作时，观察到在实验开始时，从接种刀转移到 salchichón 的单核细胞增生李斯特菌较多。此外，从接种砧板转移的单核细胞增生李斯特菌与切片数量无关，但来自塑料的污染高于木材。关于单核细胞增生李斯特菌对消毒剂的抗性，在暴露于 200ppm 氯 6 分钟后，检测到平均减少了 2.6±1.1logCFU/mL；然而，氯的抗性在菌株之间有所不同。零售销售的 RTE 肉类产品中单核细胞增生李斯特菌的流行率可能与店内处理操作有关；需要进一步研究来估计这些操作对消费者总体风险的影响。
