Roche S M, Gracieux P, Albert I, Gouali M, Jacquet C, Martin P M V, Velge P
Pathologie Infectieuse et Immunologie, Institut National de la Recherche Agronomique, 37380 Nouzilly, France.
Infect Immun. 2003 Jun;71(6):3429-36. doi: 10.1128/IAI.71.6.3429-3436.2003.
Several reports have described Listeria monocytogenes strains which were nonpathogenic or weakly pathogenic, but little is known about these low-virulence strains. We found that 9 field L. monocytogenes strains were hypovirulent and 17 were avirulent, based on the number of mice contaminated and the colonization of their spleens after subcutaneous inoculation. All these strains possessed the known virulence genes. We have now assessed the low virulence of these strains in other assays before determining how they differ from virulent strains. We have shown that the low-virulence strains exhibited a phenotypic stability and were not a mixture of virulent and avirulent bacteria. They did not recover virulence after many passages in mice and colonized the spleens of mice more poorly than virulent strains after i.v. inoculation. Their lethal capacities, determined by 50% lethal dose (LD(50)), were lower than those of virulent strains. Like Listeria innocua, 14 of 17 avirulent strains had no LD(50) and were eliminated by the lymph nodes after subcutaneous inoculation. The virulent, hypovirulent, and avirulent strains were always significantly different, whatever the tests of virulence used, confirming the importance of these low-virulence field strains in identifying the proteins involved in virulence.
已有多篇报道描述了无致病性或致病性较弱的单核细胞增生李斯特菌菌株，但对这些低毒力菌株了解甚少。基于皮下接种后小鼠受污染的数量及其脾脏的定殖情况，我们发现9株田间单核细胞增生李斯特菌菌株为低毒力菌株，17株为无毒力菌株。所有这些菌株都拥有已知的毒力基因。在确定它们与强毒力菌株的差异之前，我们现在已经在其他试验中评估了这些菌株的低毒力。我们已经表明，低毒力菌株表现出表型稳定性，并非强毒力和无毒力细菌的混合物。它们在小鼠体内多次传代后并未恢复毒力，静脉注射后在小鼠脾脏中的定殖能力比强毒力菌株差。通过50%致死剂量（LD50）测定，它们的致死能力低于强毒力菌株。与无害李斯特菌一样，17株无毒力菌株中有14株没有LD50，皮下接种后被淋巴结清除。无论使用何种毒力测试，强毒力、低毒力和无毒力菌株总是存在显著差异，这证实了这些低毒力田间菌株在鉴定毒力相关蛋白方面的重要性。
