Colonization of Lactobacillus rhamnosus GG in the Oral Cavity

Objectives: Lactobacillus rhamnosus GG (LGG) is one of the most widely studied probiotic bacterial strains. The benefits of LGG treatment of gastrointestinal disorders are well documented. However, data is sparse regarding probiotics in the oral cavity. Therefore, the aim of the present short-term intervention study was to investigate whether LGG can be detected in the oral cavity after discontinuation of administration of a product containing this bacterium. Colonization would be the first step for an anticipated long-term effect of probiotics in the mouth. We expected colonization to occur. Methods: A total of 56 volunteers (mean age 25.8±10.5 years) consumed three times daily 200 ml of LGG-containing juice (Gefilus®, Valio Ltd, Helsinki, Finland) in an open trial for 14 days. A clearance period of two weeks preceded the trial. Saliva samples were collected by the spitting method and cultured onto MRS agar daily after a two-week intervention. The sampling continued for as long as LGG was detected in the samples. LGG colonies were identified by their characteristic colony morphology, lactose fermentation test, and by use of polymerase chain reaction method with specific primers. Results: The results of this intervention study showed that LGG was not able to colonize the oral cavity after short-term consumption of the juice containing this bacterium. It could, however, be temporarily detected. After one day of intervention the number of LGG positive subjects was 66% (n=37). But after seven days of intervention LGG was found only in two samples (3.6%), and at the two-week sampling only one subject was LGG positive. Conclusion: Contrary to our study hypothesis, the consumption of LGG-containing juice did not seem to cause permanent colonization of the bacterium in the oral cavity. Consequently, for an eventual probiotic effect on the mouth the consumption of the product containing LGG should be continuous.