Effects of Probiotic Lactobacilli on Streptococcus mutans: Implications for Early Childhood Caries

Abstract

Effects of Probiotic Lactobacilli on Streptococcus mutans: Implications for Early Childhood Caries

WALAA MOHIEDEN AL TURKI DENTISTRY ABSTRACT

Purpose: Probiotic Lactobacillus species have been shown to have beneficial effects against early childhood caries (ECC) by inhibiting the growth of cariogenic bacteria. However, the acidogenicity of Lactobacillus spp. could have potential carcinogenic effect. The objective of this study was to investigate the effects of probiotic lactobacilli and cariogenic lactobacilli on the growth, biofilm formation, and acid production of Streptococcus mutans (S. mutans).

Methods: Growth competition between probiotic L. rhamnosus GG (L-GG) or caries-associated L. rhamnosus M72-26 (L-M72) and S. mutans UA159 were assessed on Todd Hewitt Yeast (THY) agar plates and De Man-Rogosa-Sharpe (MRS) agar plates. Lactobacilli and S. mutans single- and dual-species biofilm formation in THY and MRS media containing 1% sucrose were evaluated via crystal violet staining. Acid production by lactobacilli and S. mutans single- and dual-species biofilms at different time intervals were analyzed using an Orion pH meter.

Results: There was no inhibition of S. mutans growth by L-GG or L-M72 on THY agar plates; inhibition was noted only on MRS agar plates. L-GG was able to reduce S. mutans biofilm iii formation in direct assay but did not inhibit the biofilm formation in the indirect assay. In addition, the dual-species biofilm showed similar levels of acid production as lactobacilli single-species biofilms.

Conclusions: Probiotic lactobacilli may prevent ECC development by inhibiting the growth and biofilm formation of S. mutans only under favorable conditions. Further studies will evaluate the in vivo effects of L-GG on S. mutans-induced caries development in animal models.