Susceptibility of Salmonella typhimurium and Salmonella typhi to oxygen metabolites

The susceptibility of Salmonella typhimurium LT2 and S. typhi 1079 to oxygen metabolites were compared. S. typhimurium LT2 and S. typhi 1079 were killed to an equal extent (about 40%) by the xanthine-xanthine oxidase (200 mU/ml) system. Among the various scavengers of oxygen metabolites, catalase alone inhibited the killing of S. typhimurium LT2 and S. typhi 1079 by the xanthine-xanthine oxidase system, indicating that hydrogen peroxide contributed to the killing of Salmonellae. The respiratory burst of murine macrophages was efficiently triggered by the ingestion of S. typhimurium LT2, S. typhimurium SL1102, and S. typhi 1079 and all to the same extent. However, in the range of the concentration of hydrogen peroxide produced by murine macrophages, neither S. typhimurium LT2 nor S. typhi 1079 were killed. Only S. typhimurium SL1102, a rough mutant of S. typhimurium LT2, was markedly susceptible under these conditions. The findings suggest that both S. typhimurium LT2 and S. typhi 1079 are resistant to oxygen-dependent killing mechanisms.