Salivary Streptococcus mutans and Lactobacilli levels following probiotic cheese consumption in adults: A double blind randomized clinical trial*

BACKGROUND The beneficial effects of Lactobacillus species have been reported but the role of these species including Lactobacillus casei (L. casei) on oral health is not well documented. The purpose of this study was to evaluate the effects of conventional or probiotic cheese containing L.casei on salivary Streptococcus mutans (SM) and Lactobacilli levels. METHODS In this double-blind controlled trial (IRCT201009144745N1), 60 adults were randomly allocated in 2 parallel blocks. SM and Lactobacilli count assessment were performed three times. Subjects consumed either cheese containing L. casei (1×10(6)Cfu/g) (probiotic block, n=29) or cheese without any probiotic (control block, n=31) twice daily for two weeks. Bacterial levels changes were compared using Wilcoxon and Mann-Whitney Tests. Logistic regression compared changes in number of subjects with lowest and highest SM or Lactobacilli levels. RESULTS Statistically significant (p = 0.001) reduction of salivary SM was found in probiotic group. SM levels reduction was not significant between placebo and trial groups (p = 0.46, 62% in probiotic vs. 32% in placebo group). Lacto-bacilli count changes during trial were not statistically significant inter and intra blocks (p = 0.12). Probiotic intervention was significantly effective in high levels (> 10(5)cfu/ml) of SM (Odds Ratio 11.6, 95% CI 1.56-86.17, p = 0.017). CONCLUSIONS Probiotic cheese containing L. casei was not effective in salivary SM levels reduction comparing to conventional cheese. Adding L. casei to cheese could be useful in decreasing SM counts in adults 18-37 years old with highest level of SM.