Probiotics as a Means to Reduce the Incidence of Streptococcus Mutans
Data from a prospective study examining the effects of probiotics on the oral microbiome show the ability of orally administered probiotics to reduce the incidence of Streptococcus mutans and also positively affect the presence of lactobacilli in the oral cavity.
Probiotics and Oral Health
Probiotics are commonly associated with gastrointestinal health, but in recent decades, several potential applications of bacteriotherapy have also been proposed concerning oral health. Probiotics are defined as live microorganisms, most commonly of the genus Lactobacillus or Bifidobacterium, which can positively impact both gut and oral health. They can be used as effector strains and have also been widely evaluated for caries prevention.
Several clinical studies have investigated the role of these probiotic microorganisms in inhibiting Streptococcus mutans, which is considered one of the most common microorganisms related to dental caries. Most studies have shown the effect of administering probiotics in various forms (lozenges, food additives, drops) on reducing the incidence of S. mutans; however, a few had the opposite result. Concurrently, most studies demonstrated that following the cessation of probiotics application, the state of the oral microflora began to return to its original values, and the number of surviving probiotic bacteria gradually decreased.
The aim of the below-illustrated evaluation was to explore the potential for oral colonization after 4 weeks of administering Lactobacillus reuteri and the short-term effect of probiotics on Streptococcus mutans and lactobacilli present in saliva.
Methodology and Study Course
The short-term prospective clinical study lasted 9 weeks and consisted of a 4-week intervention period with probiotics administered twice daily, followed by a 5-week follow-up without probiotics consumption. The study group consisted of 13 young adults (7 women and 6 men) with an average age of 25.7 (± 3.6) years. Inclusion criteria included the absence of systemic disease, non-use of any medication, non-smoking, and the presence of S. mutans in saliva > 104 CFU/ml. Probiotics were administered in the form of oral probiotic drops containing lyophilized L. reuteri DSM 17938 (> 108 CFU/5 drops) and L. reuteri ATCC PTA 5289 (> 108 CFU/5 drops) suspended in oil. The daily dosage was 0.15–0.20 g (5 drops).
Saliva and dental biofilm samples were collected immediately before probiotic administration, after 2 weeks, and after 4 weeks of L. reuteri administration. Control samples were taken regularly once a week after the application ended. The numbers of S. mutans and lactobacilli in saliva were evaluated by regular plating on culture plates, while the presence of both L. reuteri strains in saliva and dental biofilm was determined using quantitative polymerase chain reaction (qPCR).
To compare different time points from baseline to the 9th week and detect S. mutans, lactobacilli, and the 2 probiotic strains in saliva, researchers performed a one-way analysis of variance (ANOVA) with Tukey's post hoc test. A p-value < 0.05 was considered statistically significant.
Results
The presence of L. reuteri in the oral cavity gradually increased during the intervention period, peaking after 4 weeks of probiotics administration (p < 0.0001). Stimulated saliva samples taken after 4 weeks of probiotics usage showed a statistically significant decrease in S. mutans and a statistically significant increase in the number of lactobacilli in saliva compared to baseline.
Probiotic bacteria gradually began to disappear from week 1 of the follow-up, and 5 weeks after the intervention, only 4 individuals still had the DSM 17938 strain, and two had the PTA 5289 strain. Analysis of qPCR from plaque showed a similar trend.
Conclusion
Probiotics administered in the form of diluted drops used as mouthwash were detected in saliva and biofilm during usage but could not establish themselves in the oral cavity after a shorter exposure. They also demonstrated the ability to reduce the number of S. mutans in saliva. In future studies, the authors suggest it would be interesting to observe the effect on various variables associated with dental caries and the actual outcome in individuals with different caries activity levels.
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Source: Alforaidi S., Bresin A., Almosa N. et al. Oral colonisation after the administration of drops containing Lactobacillus reuteri. Oral Health Prev Dent 2020; 18 (1): 1017–1023, doi: 10.3290/j.ohpd.a45523.
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