Diet Genomics and Immunology and Laboratory, Henry A. Wallace Beltsville Agricultural Research Center, Agricultural Research Service, USDA, 10300 Baltimore Avenue, BARC-E, Beltsville, MD 20705-2350, USA.
Curr Microbiol. 2013 May;66(5):522-6. doi: 10.1007/s00284-012-0298-x. Epub 2013 Jan 18.
Enhanced virulence or infectivity after passage through a mammalian host has been reported for a number of enteric food-borne pathogens. Citrobacter rodentium is a mouse pathogen that mimics many aspects of enterohemorrhagic Escherichia coli infection of humans and serves as a useful model for studying virulence mechanisms. Emergence of a hyperinfectious state after passage through mouse gastrointestinal tract was reported for C. rodentium. We wanted to investigate if increased acid tolerance could explain hypervirulence status of C. rodentium. Although we were able to observe hyperinfectious state of C. rodentium upon host passage, the cells were extremely acid sensitive. Growth under mildly acidic conditions (LB-MES, pH 5.5) induced acid tolerance of C. rodentium, but did not improve the organism's ability to establish infection. Growth under anaerobic environment on fecal components also did not induce hyperinfectious state. Thus, contrary to conventional anticipation, hypervirulent C. rodentium cells were found to be acid sensitive thereby revealing limitations of the role of mouse gastric acidity by itself in elucidating the hypervirulent phenotype.
有报道称，许多肠道食源性病原体在经过哺乳动物宿主后会增强其毒力或感染力。鼠伤寒沙门氏菌是一种鼠病原体，它模拟了人类肠出血性大肠杆菌感染的许多方面，是研究毒力机制的有用模型。鼠伤寒沙门氏菌在经过小鼠胃肠道后会出现超感染状态。我们想研究一下耐酸性增加是否可以解释鼠伤寒沙门氏菌的高毒力状态。尽管我们能够观察到宿主传代后鼠伤寒沙门氏菌的超感染状态，但这些细胞对酸极为敏感。在轻度酸性条件（LB-MES，pH5.5）下生长会诱导鼠伤寒沙门氏菌的耐酸性，但不能提高该生物体建立感染的能力。在粪便成分的厌氧环境下生长也不会诱导超感染状态。因此，与传统预期相反，我们发现高毒力鼠伤寒沙门氏菌细胞对酸敏感，从而揭示了小鼠胃酸度本身在阐明高毒力表型中的作用的局限性。
