背景:李斯特菌(L.)单核细胞增生菌株在胁迫耐受性和毒力潜力方面表现出很高的多样性。基因组研究主要集中在主要与食物或人类李斯特菌病相关的特定序列类型(ST)。这项研究集中在流行的ST155上,显示出临床和食物分离株之间的分布相等。我们评估了20个ST155菌株的毒力潜力,并对从食物中分离的130个ST155菌株进行了比较基因组分析,不同国家和年份的食品加工环境和人类李斯特菌病病例。
结果:使用人肠上皮Caco2和肝细胞HEPG2细胞的体外毒力测定显示,20个选定的ST155菌株中有6个毒力表型受损。基因组分析显示,来自同一来源类别的菌株没有明显的聚类(食物,食品加工环境,和临床分离株)。所有菌株都有完整的inlA和inlB基因座,除了四个菌株,inlA基因有一个内部缺失.所有菌株都含有LIPI-1,但prfA在六个菌株中以更长的变体存在,都表现出毒力受损。更长的PrfA变体导致inlA表达降低,inlb,和prfa,没有hly和acta的表情.关于应激相关基因含量,SSI-1在场,而qacH在所有菌株中均不存在。34.6%的菌株携带质粒。除一个ST155质粒外,所有质粒均显示出高保守性,并带有cadA2,bcrABC,和三苯甲烷还原酶.
结论:这项研究有助于增强对单核细胞增生李斯特菌ST155菌株的了解,在人类的分离株中均匀分布,食物,和食品加工环境。当前遗传性状的保守性和缺乏独特的固有遗传特征使得这些类型的STs特别有趣,因为它们显然同样适应食品加工环境中的条件。以及食物中的人类宿主环境。然而,导致较长PrfA变体的ST155特异性突变损害了几种ST155菌株的毒力潜力。
BACKGROUND: Listeria (L.) monocytogenes strains show a high diversity regarding stress tolerance and virulence potential. Genome studies have mainly focused on specific sequence types (STs) predominantly associated with either food or human listeriosis. This study focused on the prevalent
ST155, showing equal distribution among clinical and food isolates. We evaluated the virulence potential of 20
ST155 strains and performed comparative genomic analysis of 130 ST155 strains isolated from food, food processing environments and human listeriosis cases in different countries and years.
RESULTS: The in vitro virulence assays using human intestinal epithelial Caco2 and hepatocytic HEPG2 cells showed an impaired virulence phenotype for six of the 20 selected ST155 strains. Genome analysis revealed no distinct clustering of strains from the same source category (food, food processing environment, and clinical isolates). All strains harbored an intact inlA and inlB locus, except four strains, which had an internal deletion in the inlA gene. All strains harbored LIPI-1, but prfA was present in a longer variant in six strains, all showing impaired virulence. The longer PrfA variant resulted in lower expression of inlA, inlB, and prfA, and no expression of hly and actA. Regarding stress-related gene content, SSI-1 was present, whereas qacH was absent in all strains. 34.6% of the strains harbored a plasmid. All but one
ST155 plasmids showed high conservation and harbored cadA2, bcrABC, and a triphenylmethane reductase.
CONCLUSIONS: This study contributes to an enhanced understanding of L. monocytogenes
ST155 strains, being equally distributed among isolates from humans, food, and food processing environments. The conservation of the present genetic traits and the absence of unique inherent genetic features makes these types of STs especially interesting since they are apparently equally adapted to the conditions in food processing environments, as well as in food as to the human host environment. However, a ST155-specific mutation resulting in a longer PrfA variant impaired the virulence potential of several
ST155 strains.