Evaluation of Salmonella typhimurium mutants in a model of experimental gastroenteritis

Salmonella typhimurium strains harboring independent, defined mutations in aroA, invA, ssrA, or msbB were assessed for their ability to induce fluid a ccumulation, tissue damage, and local inflammation in rabbit ileal loops. T hree wild-type strains of S. typhimurium, TML, HWSH, and SL1344, and two mu tant strains, S. typhimurium SL1344 ssrA and S. typhimurium SL1344 msbB, co nsistently induced fluid accumulation in the lumen of loops and inflammatio n of loop-associated tissues. In contrast, three different S. typhimurium a roA strains and an invA mutant of SL1344 did not induce significant fluid a ccumulation in the rabbit ileal loops. However, the S. typhimurium aroA str ains did induce an inflammatory infiltrate and some local villus-associated damage, but the invA mutant did not. Histologically, wild-type S. typhimur ium, S. typhimurium SL1344 ssrA, and S. typhimurium SL1344 msbB demonstrate d more severe effects on villus architecture than S. typhimurium aroA strai ns, whereas S. typhimurium invA-infected loops showed no detectable damage. This suggests that villus damage most likely contributes to fluid accumula tion within the loop.