Inhibition of Streptococcus mutans Biofilm Formation and Virulence by Lactobacillus plantarum K41 Isolated From Traditional Sichuan Pickles

Abstract

Among cariogenic microbes, <i>Streptococcus mutans</i> is considered a major etiological pathogen of dental caries. <i>Lactobacilli</i> strains have been promoted as possible probiotic agents against <i>S. mutans</i>, although the inhibitory effect of <i>Lactobacilli</i> on caries has not yet been properly addressed. The objective of this study was to screen <i>Lactobacillus</i> strains found in traditional Sichuan pickles and to evaluate their antagonistic properties against <i>S. mutans in vitro</i> and <i>in vivo</i>. In the current study, we analyzed 54 <i>Lactobacillus</i> strains isolated from pickles and found that strain <i>L. plantarum</i> K41 showed the highest inhibitory effect on <i>S. mutans</i> growth as well as on the formation of exopolysaccharides (EPS) and biofilm <i>in vitro</i>. Scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) revealed the reduction of both EPS and of the network-like structure in <i>S. mutans</i> biofilm when these bacteria were co-cultured with strain <i>L. plantarum</i> K41. Furthermore, when rats were treated with strain <i>L. plantarum</i> K41, there was a significant reduction in the incidence and severity of dental caries. Due to K41's origin in a high salinity environment, it showed a high tolerance to acids and salts. This may give this strain an advantage in harsh oral conditions. Results showed that <i>L. plantarum</i> K41 isolated from traditional Sichuan pickles effectively inhibited <i>S. mutans</i> biofilm formation and thus possesses a potential inhibitory effect on dental caries <i>in vivo</i>.