Evaluation of the effect of streptococcus salivarius K12 use on oral health

Probiotic microorganisms are known as beneficial microorganisms and their healing effect on general health and supportive effect on immun system have been shown by studies. There are controversial results regarding its effect on the oral microbiota and the prevention of dental biofilm formation, which is the microbial layer that accumulates on teeth and surrounding soft tissues. Therefore, the primary aim of this study was to evaluate the effect of the use of an oral probiotic known as Streptococcus salivarius K12 on the number of Streptococcus mutans and Lactobacillus species in the oral microbiota changed after the cariogenic diet. Secondary aim was to evaluate whether the similar effect continues after the probiotic was discontinued. This thesis was a randomized, controlled, follow-up and cross-sectional animal study. Three-five month old, female, 32 Sprague-Dawley rats were included in the study and distributed into 4 groups according to the administration of cariogenic diet and probiotics. These groups were: (G1) Cariogenic diet and probiotics administreted, (G2) Only cariogenic diet administered, (G3) Only probiotics administered, (G4) Group without administration of cariogenic diet and probiotics. The rats included in the study were fed with a sucrose-based bait for 2 months in the groups that received cariogenic diet. Probiotic administered groups were allowed to drink probiotic tablet dissolved water containing S. salivarius K12 for 1 month. During the 2-month follow-up period, intraoral samples were taken from all included rats using pipetting method before the start of the experiment (T0), at the end of the 1-month (T1) and 2-month (T2) follow-up period. DNA was isolated from all samples and quantitative amounts of S. mutans, S. salivarius and Lactobacillus species in the DNA isolates were analyzed by real-time quantitative polymerase chain reaction (qPCR). Primer and probe designs specific to S. mutans, S. salivarius and Lactobacillus species to be used during real-time qPCR analysis were produced and all reactions, including standard samples, were run in duplicate using TaqMan probes. In the intergroup comparison of the data obtained from real-time qPCR analysis, data for Lactobacillus species were tested with Friedman ranked two-way variance analysis, and S. salivarius data were tested with Kruskal-Wallis analysis of variance. In the intra-group evaluation of S. salivarius data, statistical analyzes were performed using Friedman ranked two-way analysis of variance and Dependent Sample T-test. Statistical significance level was accepted as p<0.05. As a result of statistical analysis, no statistical difference was observed between the groups in the samples taken during T0 (p=0.131; p≥0.05), T1 (p=0.676; p≥0.05) and T2 (p=0.435; p≥0.05) periods for Lactobacillus species, and no statistical difference was observed for each group G1 (p=0.430; p≥0.05), G2 (p=0.325; p≥0.05), G3 (p=0.882; p≥0.05) and G4 (p=0.368; p≥0.05) when evaluated in terms of its change over time. As a result of the statistical analysis of S. salivarius data, no statistical difference was observed for T0 (p=1; p≥0.05) period but, statistical difference was observed between the groups during T1 (p<0.05) and T2 (p<0.05) periods, and statistically significant increase was seen in all groups that administered probiotics (G1-G2: p=0.002, G1-G4: p=0.002, G2-G3: p=0.001, G3 -G4: p=0.001; p<0.05). According to the intra-group comparison results for S. salivarius, there was a statistical difference between the samples taken at different follow-up periods for T0-T1 (p=0.018; p<0.05), T0-T2 (p=0.003; p<0.05) and T0-T1 (p=0.03; p<0.05), T0-T2 (p=0.043; p<0.05); while there was no statistical difference between T1-T2 (p=1; p≥0.05) and T1-T2 (p=0.448; p≥0.05) samples for G1 and G3, respectively. S. mutans colonization was not observed in the groups. According to the results of this study conducted on animals, it was observed that S. salivarius colonization was at a significantly higher level in the groups using probiotics and its effect continued even after the probiotic was discontinued. In addition, it was found that the number of Lactobacillus species was affected by both cariogenic diet and probiotic administration. In conclusion, this is a pioneer study for in-vivo studies as it evidences the colonization of S. salivarius K12 probiotic microorganisms in the oral microbiota even after the discontinuation of probiotics.