Date Published: February 8, 2018
Publisher: Public Library of Science
Author(s): Ki Bum Ahn, Jung Eun Baik, Ok-Jin Park, Cheol-Heui Yun, Seung Hyun Han, José A. Lemos.
Dental caries is a biofilm-dependent oral disease and Streptococcus mutans is the known primary etiologic agent of dental caries that initiates biofilm formation on tooth surfaces. Although some Lactobacillus strains inhibit biofilm formation of oral pathogenic bacteria, the molecular mechanisms by which lactobacilli inhibit bacterial biofilm formation are not clearly understood. In this study, we demonstrated that Lactobacillus plantarum lipoteichoic acid (Lp.LTA) inhibited the biofilm formation of S. mutans on polystyrene plates, hydroxyapatite discs, and dentin slices without affecting the bacterial growth. Lp.LTA interferes with sucrose decomposition of S. mutans required for the production of exopolysaccharide, which is a main component of biofilm. Lp.LTA also attenuated the biding of fluorescein isothiocyanate-conjugated dextran to S. mutans, which is known to have a high affinity to exopolysaccharide on S. mutans. Dealanylated Lp.LTA did not inhibit biofilm formation of S. mutans implying that D-alanine moieties in the Lp.LTA structure were crucial for inhibition. Collectively, these results suggest that Lp.LTA attenuates S. mutans biofilm formation and could be used to develop effective anticaries agents.
A biofilm is a dense community of bacteria attached to an organic or inorganic surface. Generally, bacteria in the biofilm are enclosed in an extracellular polymeric substance matrix of polysaccharides, proteins, extracellular DNA, and metabolites . During the transition from planktonic to biofilm bacteria, a variety of physiological characteristics change. Genes associated with adhesion molecules or exopolysaccharide (EPS) and antibiotic-resistance genes are increased in biofilm bacteria . Bacteria in biofilms are known to be 10- to 1000-times more resistant to antibiotics and antimicrobial peptides than planktonic bacteria. Biofilm bacteria can avoid phagocytosis by macrophages or neutrophils [3, 4]. Accordingly, biofilms are a public health concern due to increased resistance to antibiotics that limits treatment options.
In this study, we demonstrated that LTA released from L. plantarum inhibited biofilm formation of S. mutans, a representative pathogen that causes dental caries. Mechanistic studies showed that biofilm formation was inhibited by Lp.LTA and mediated through suppression of EPS production. D-Alanine in Lp.LTA was a key functional moiety for eliciting the inhibition.