THE ROLE OF INTESTINAL MICROFLORA ON THE PREVENTION OF SALMONELLA COLONIZATION IN GNOTOBIOTIC CHICKENS

The possible role of the intestinal microflora in inhibiting the colonization of Salmonella in the ceca of gnotobiotic chickens was investigated. In the cecal contents of newly hatched (2-day-old) and adult normal (7-mo-old) chickens, a larger number of Escherichia coli and a smaller number of Lactobacillus sp. were noticed in 2-day-old chickens than in adult chickens. Gnotobiotic chickens treated with cecal contents from either newly hatched or adult birds were orally exposed to Salmonella typhimurium, and on the following day S. typhimurium in the ceca were counted. The adult microflora prevented S. typhimurium colonization more strongly than did the microflora of newly hatched chicks. Gnotobiotic chickens treated with E. coli, Lactobacillus sp., or the mixture of both organisms were orally inoculated with S. typhimurium. The mixture of both organisms suppressed S. typhimurium colonization most effectively, followed by E. coli alone and Lactobacillus sp. alone. Escherichia coli may play a role of competitive exclusion only in newly hatched chickens, whereas Lactobacillus sp. may have a partial role in adult chickens.