Liu Xin, Shi Tianqi, Li Jiaming, Wu Huanyu, Zhao Qing, Fang Zhixin, Liang Yingying, Xiao Quan, Chen Min, Dong Qingli, Zhang Hongzhi
School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China.
Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China.
Food Microbiol. 2025 Mar;126:104675. doi: 10.1016/j.fm.2024.104675. Epub 2024 Oct 28.
Listeria monocytogenes is a major foodborne pathogen. In our previous study, we found that L. monocytogenes ST5 and ST121 strains were dominant in two food plants of Shanghai. Genetic characterization revealed that the environmental tolerance of these strains was attributable to the plasmids pLM33 and pLM5578. To further evaluate the function of L. monocytogenes plasmids, we selected ST5 and ST121 wild-type strains, and used their plasmid-cured strains as controls to conduct tolerance tests. In addition, we analyzed 108 L. monocytogenes strains isolated from four major food categories in Shanghai. Our results showed that compared with the plasmid-cured strain, the ST5 strain carrying pLM33 showed higher tolerance to environmental stress conditions, including low acid, high salt, oxidizing, and high-temperature conditions; as well as higher virulence. Furthermore, we found that the plasmid carriage rate of food isolates was 97.22%, with the highest carriage rate of 68.57% for pLM5578, followed by 24.76% for pLM33. Notably, all L. monocytogenes ST5 isolates from ready-to-eat food products (n = 11) carried plasmids, suggesting that contamination of these food products may pose a serious risk to human health. In summary, the results of this study broaden our understanding regarding the role of L. monocytogenes plasmids in stress responses.
单核细胞增生李斯特菌是一种主要的食源性病原体。在我们之前的研究中，我们发现单核细胞增生李斯特菌ST5和ST121菌株在上海的两家食品工厂中占主导地位。遗传特征分析表明，这些菌株对环境的耐受性归因于质粒pLM33和pLM5578。为了进一步评估单核细胞增生李斯特菌质粒的功能，我们选择了ST5和ST121野生型菌株，并以其质粒消除菌株作为对照进行耐受性试验。此外，我们分析了从上海四大类主要食品中分离出的108株单核细胞增生李斯特菌菌株。我们的结果表明，与质粒消除菌株相比，携带pLM33的ST5菌株对包括低酸、高盐、氧化和高温条件在内的环境应激条件具有更高的耐受性；以及更高的毒力。此外，我们发现食品分离株的质粒携带率为97.22%，其中pLM5578的携带率最高，为68.57%，其次是pLM33，为24.76%。值得注意的是，即食食品中所有的单核细胞增生李斯特菌ST5分离株（n = 11）都携带质粒，这表明这些食品的污染可能对人类健康构成严重风险。总之，本研究结果拓宽了我们对单核细胞增生李斯特菌质粒在应激反应中作用的理解。
