熟肉制品中单核细胞增生李斯特氏菌耐药及致病的遗传分析

目的 获得中国不同省份熟肉制品中的33株单核细胞增生李斯特氏菌(单增李斯特菌)的抗生素敏感性特征图谱,并运用全基因组测序对菌株进行耐药和致病的基因遗传分析。方法 采用微量肉汤稀释法对33株熟肉制品中的单增李斯特菌进行药敏测定,同时进行高精度框架图测序,基因组序列经组装后通过相应的生物信息学流程进行数据分析。结果 33株单增李斯特菌对于氨苄青霉素、复方新诺明、庆大霉素、万古霉素、美罗培南共计5种抗生素结果均为敏感。1株单增李斯特菌耐受2种抗生素,分别为四环素和红霉素。全基因组测序分析表明:33株单增李斯特菌分属13个多位点序列分型(MLST)型别,其中ST9、ST87和ST121为主要型别,耐药株为ST87型。耐药株基因型与表型相关联。耐药基因上下游遗传环境分析表明,这些基因的可能来源为猪丹毒杆菌或Blautia producta。所有分离株均携带致病基因岛LIPI-1和LIPI-2,7株携带LIPI-3,8株携带LIPI-4(1株ST121、7株ST87)。结论 熟肉制品中单增李斯特菌存在获得性耐药,同时由于其携带了更多的毒力基因而产生潜在的高致病性菌株。本研究表明应加强对熟肉制品中单增李斯特菌,尤其是ST87型的监测和风险评估。

Antimicrobial and pathogenic characterization of Listeria monocytogenes isolated from ready-to-eat meats

Objective To determine the antimicrobial susceptibilities of 33 Listeria monocytogenes cultured from ready-to-eat (RTE) meats in China and to use whole genome sequencing (WGS) to characterize the antimicrobial resistance and virulence genotypes of these isolates. Methods The susceptibilities of 33 Listeria monocytogenes were determined by broth microdilution. These isolates were then sequenced using short-read high accuracy protocols. The corresponding genomes were assembled and further analysis was carried out using appropriate bioinformatics pipelines. Results All isolates were found to be susceptible to ampicillin, trimethoprim-sulfamethoxazole, gentamicin, meropenem and vancomycin. One isolate was resistant to tetracycline and erythromycin at the same time. All 33 L. monocytogenes were classified into 13 STs, among them ST9, ST87, ST122 were the dominant, from which resistant isolate belonged to ST87. The genotypes of the resistant isolate correlated well with its resistant phenotype. Up and down stream analysis of the genetic context, in which these resistant genes were found, suggested that they may have been acquired from Erysipelothrix rhusiopathiae and Blautia product. All isolates harboured LIPI-1 and LIPI-2,7 of them harbored LIPI-3, and 8 harboured LIPI-4(1 ST121 and 7 ST87). Conclusion These data showed that acquired resistance existed in this bacterium from RTE meats origins, and can be a potential public health risk due to its high harboring rate of LIPI-3 and LIPI-4. It was suggested that the monitoring of L. monocytogenes in RTE meats should be strengthened in the future, specifically for ST87.