ASalmonella typhimuriummutant unable to utilize fatty acids and citrate is avirulent and immunogenic in mice

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Abstract
Salmonella typhimurium SR-11 is extremely virulent at a dose as low as 105 colony forming units (cfu) when administered perorally to BALB/c mice. Utilizing mini-transposon mutagenesis, a mutant of S. typhimurium SR-11 was isolated that was unable to utilize oleate and citrate as carbon sources. This mutant, designated S. typhimurium SR-11 Fad− (Fatty acid), was found to utilize sugars under cya/crp control as sole carbon sources, suggesting that the mutation is not in either of these genes. In addition, SR-11 Fad− utilized pyruvate and succinate, but was unable to utilize either acetate or isocitrate as sole carbon source. In contrast to SR-11, SR-11 Fad− was found to be avirulent, i.e. BALB/c mice were completely healthy after oral infection with 109S. typhimurium SR-11 Fad− cells. Moreover, 21 days after SR-11 Fad− infection, BALB/c mice were found to be protected against an oral challenge with 109 cells of S. typhimurium SR-11.