Survival of Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus in the terminal ileum of fistulated Gottingen minipigs

The ability of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcu s thermophilus administered in yogurt to survive the passage through the up per gastrointestinal tract was investigated with Gottingen minipigs that we re fitted with ileum T-cannulas. After ingestion of yogurt containing viabl e microorganisms, ileostomy samples were collected nearly every hour beginn ing 3 h after food uptake. Living L. delbrueckii subsp. bulgaricus and S. t hermophilus were detected in the magnitude of 10(6) to 10(7) per gram of in testinal contents (wet weight) in all animals under investigation. A calcul ation of the minimum amount of surviving bacteria that had been administere d is presented. Total DNA extracted from ileostomy samples was subjected to PCR, which was species specific for L. delbrueckii and S. thermophilus and subspecies specific for L. delbrueckii subsp. bulgaricus. All three bacter ial groups could be detected by PCR after yogurt uptake but not after uptak e of a semisynthetic diet. One pig apparently had developed an endogenous L . delbrueckii flora. When heat-treated yogurt was administered, L. delbruec kii was detected in all animals. S. thermophilus or L. delbrueckii subsp. b ulgaricus was not detected, indicating that heat-inactivated cells and thei r DNAs had already been digested and their own L. delbrueckii flora had bee n stimulated for growth.