Interfering effect of Isospora suis infection on Salmonella typhimurium infection in swine.

Piglets were each orally inoculated daily for 4 consecutive days, with 10(4)-10(5) nalidixic acid-resistant Salmonella typhimurium and, starting 1 day after inoculation, with 50 000 Isospora suis sporulated oocysts. Control pigs were given S. typhimurium alone following the same inoculation schedule. Fecal samples were taken 5, 7 and 10 days after the coccidial inoculation, and all the pigs were necropsied 13 days after inoculation. S. typhimurium counts in the feces and in the cecal contents and the numbers of pigs positive for presence of S. typhimurium in the mesenteric lymph nodes of the dual-infected pigs were significantly (P less than 0.05) smaller than in those infected with S. typhimurium alone.