Gorden J, Small P L
Middlebury College, Vermont 05753.
Infect Immun. 1993 Jan;61(1):364-7. doi: 10.1128/iai.61.1.364-367.1993.
Shigella species require a uniquely small inoculum for causing dysentery. One explanation for the low infective dose is that Shigella species are better able to survive the acidic conditions encountered in the stomach than are other enteric pathogens. We have tested Shigella species, Escherichia coli, and Salmonella species for the ability to survive at pH 2.5 for at least 2 h. Most isolates of Shigella and E. coli survived this treatment, whereas none of the Salmonella isolates were able to do so. The ability of Shigella species to survive at low pHs does not require the presence of the large virulence plasmid or growth at 37 degrees C but is strikingly dependent on growth phase. We have also found that Shigella isolates exposed to acid lose the ability to invade epithelial cells.
志贺氏菌属引起痢疾所需的接种量特别少。感染剂量低的一种解释是，与其他肠道病原体相比，志贺氏菌属在胃中遇到的酸性条件下更能存活。我们测试了志贺氏菌属、大肠杆菌和沙门氏菌属在pH 2.5下存活至少2小时的能力。大多数志贺氏菌和大肠杆菌分离株在这种处理下存活下来，而所有沙门氏菌分离株均无法存活。志贺氏菌属在低pH值下存活的能力并不需要大型毒力质粒的存在或在37摄氏度下生长，但显著依赖于生长阶段。我们还发现，暴露于酸性环境的志贺氏菌分离株失去了侵袭上皮细胞的能力。
