天然缺失inlAB的非典型单核细胞增多性李斯特菌生物学特性鉴定

Characterization of a naturally atypical Listeria monocytogenes strain lacking inlAB

【目的】InlA与InlB是单核细胞增多性李斯特菌重要的毒力因子,其介导的黏附作用是细菌建立感染的前提。本研究拟探明天然缺失inlAB基因簇的非典型单增李斯特菌的表型与基因型特征。【方法】针对inlAB天然缺失株S10,进行生化特征、细胞黏附力、小鼠体内毒力、感染相关基因检测、谱系分析等。【结果】S10株为具有典型单增李斯特菌生化特征的1/2b型菌株,对HeLa细胞的黏附力显著低于其他菌株(P<0.05),对小鼠毒力较弱。S10缺失inlAB及与其毗邻的lmo0431、lmo0432、lmo0436、lmo0437基因,但具有李斯特菌第一毒力岛中完整的毒力基因构成。S10分布于谱系Ⅰ的进化枝上,与4b型菌株的遗传距离较近。【结论】S10为单增李斯特菌inlAB天然缺失株,代表该类非典型菌株的首次报道。S10具有典型的单增李斯特菌谱系Ⅰ基因背景,inlAB可能通过独立的重组或水平转移事件缺失于基因组。

[ Objective] We attempted to gain insights into the phenotypic and genetic characteristics of a naturally atypical Listeria monocytogenes strain S10 lacking inlAB. [ Methods] The isolate S10, together with 7 L. monocytogenes strains representing different serovars, were studied by biochemical profiling, adhesion assay in HeLa cells, virulence to mice, detection of virulence-associated genes detection and genetic lineage analyses. [ Results] The S10 isolate belonged to lineage Ⅰ and serovar 1/2b, with carbohydrate fermentation and hemolytic characteristics typical of L. monocytogenes. However, this strain had reduced adhesion to HeLa cells and decreased pathogenicity to mice. It lacked the gene locus inlAB and their adjacent genes lmo0431, lmo0432, Imo0436 and lmo0437, but contained an almost whole set of infection-associated genes. S10 fell into the lineage Ⅰ cluster and form a sister branch with 4b strain. [ Conclusion] The isolate S10 represents the first report of atypical L. monocytogenes lacking inlAB. As it lacked the inIAB locus from an otherwise typical lineage Ⅰ genetic background, inIAB was probably lost from the genome via independent deletion event.