Polymerase chain reaction detection of Lactobacillus acidophilus in human oral cavity and fecal samples after 2-week consumption of yoghurt.

Objective: To investigate whether short-term daily consumption of yoghurt leads to colonization by Lactobacillus acidophilus in a group of human subjects who were initially totally devoid of L. acidophilus in their oral cavities.

Material And Methods: Twenty-three volunteers consumed yogurt containing L. acidophilus during a 14-day trial stage. Oral and fecal samples were collected at the clearance stage and at the post-yoghurt intake stage until L. acidophilus was found. Standard polymerase chain reaction methods using specific primers were adopted for the detection and identification of L. acidophilus.

Results: The isolation frequency decreased rapidly 72 h after stopping intake of yoghurt. After 1 week, L. acidophilus was absent in all oral samples. Non-significant differences were found between the survival rates of L. acidophilus in samples of saliva, plaque, tongue surface, and buccal mucosa. L. acidophilus was also found to remain in the gastrointestinal tract for longer than in the oral cavity.

Conclusion: Allochthonous L. acidophilus is not likely to permanently colonize the oral cavity and intestine.