Division of Microbiology, Osaka Institute of Public Health, Osaka, Japan.
J Appl Microbiol. 2018 Mar;124(3):899-909. doi: 10.1111/jam.13692. Epub 2018 Feb 6.
We investigated whether Listeria monocytogenes strains differ in their ability to escape from the primary phagosome after internalization into human intestinal epithelial cells.
Food and clinical strains were used to study specific alleles; the activities of listeriolysin O (LLO) and phospholipases PlcA and PlcB, which promote rupture of the phagocytic vacuole; and initial intracellular bacterial growth in Caco-2 cells. Results showed no difference in LLO activities between food and clinical strains or among serotypes. In contrast, the LLO truncation mutant lacked detectable haemolytic activity and intracellular growth. PlcA and PlcB produced by the strains of serotypes 4b/4e and 1/2b exhibited significantly lower activities than those of serotypes 1/2a and 1/2c. In contrast, the strains of serotype 1/2b grew significantly faster than those of serotypes 4b/4e and 1/2a. Moreover, the PrfA truncation mutants lacked LLO and phospholipases activities and did not show intracellular growth.
We determined that LLO and PrfA mutants exert a significant effect on intracellular growth, although it was unclear from this study whether PlcA and PlcB alleles affect escape from vacuoles.
This study estimates that low-virulence L. monocytogenes strains associated with escape ability from the primary vacuoles are not widely distributed among food strains.
我们研究了李斯特菌（Listeria monocytogenes）菌株在被人肠道上皮细胞内化后，从初级吞噬体中逃逸的能力是否存在差异。
利用食品和临床菌株来研究特定等位基因；研究李斯特菌溶血素 O（LLO）和磷脂酶 PlcA 和 PlcB 的活性，这些酶可促进吞噬泡破裂；并研究 Caco-2 细胞中的初始细菌内生长情况。结果表明，LLO 活性在食品菌株和临床菌株之间或在血清型之间没有差异。相比之下，LLO 截断突变体缺乏可检测的溶血活性和细胞内生长。血清型 4b/4e 和 1/2b 的菌株产生的 PlcA 和 PlcB 的活性明显低于血清型 1/2a 和 1/2c。相比之下，血清型 1/2b 的菌株生长速度明显快于血清型 4b/4e 和 1/2a。此外，PrfA 截断突变体缺乏 LLO 和磷脂酶活性，并且不显示细胞内生长。
我们确定 LLO 和 PrfA 突变体对细胞内生长有显著影响，尽管本研究尚不清楚 PlcA 和 PlcB 等位基因是否影响从空泡中逃逸。
本研究估计与从初级空泡中逃逸能力相关的低毒李斯特菌（Listeria monocytogenes）菌株在食品菌株中并不广泛分布。
