Protection of chicks against Salmonella infection with a mixture of pure cultures of intestinal bacteria.

A mixture of 28 pure cultures was prepared from the organisms isolated from native gut microflora (fecal and cecal contents) of adult Salmonella-free birds. This mixture was orally administered to 1-day-old chicks and examined for its efficacy against challenge with 10(5) colony-forming units of nalidixic-acid-resistant Salmonella typhimurium in six consecutive trials during a 20-month period. The efficacy of the mixture, which was prepared for each trial from stored isolates, progressively decreased, while that from stored fecal content remained unimpaired. Twenty-three cultures in the mixture were tentatively identified as belonging to seven different genera; the genus of the five other cultures remained unknown.