Purpose: Consumption of refined foods and beverages high in sugar make the teeth susceptible to the formation of biofilm and may lead to dental caries. The aim of the present study was to determine the ability of selected probiotics to inhibit growth and biofilm formation by the cariogenic bacterium Streptococcus mutans in vitro.
Materials and methods: Strains of latic acid bacteria (LAB) (n = 120) from the Bioresources Collection and Research Center (BCRC), saliva of healthy adults and infant stool were screened. The antimicrobial activity of LAB in vitro was evaluated by agar spot culture and co-culture of the S. mutans strains. Antagonistic substances in the spent culture suspensions (SCS) of LAB were precipitated by extraction with ammonium sulphate and chloroform to characterise the protein and lipophilic fractions.
Results: Results of co-culturing show that the SCS of the three LAB strains (Lactobacillus pentosus 13-1, 13-4 and L. crispatus BCRC 14618) subjected to heat treatment showed statistically significantly higher antimicrobial activity. Substances produced by L. pentosus 13-4 which have the potential to exhibit antimicrobial properties might be lipophilic proteins. Additionally, microtiter plate biofilm assays indicated that in vitro biofilm formation by S. mutans is strongly modulated by L. pentosus 13-4 and L. crispatus BCRC 14618.
Conclusion: It can be inferred that the mechanism of reducing biofilm formation by these two LAB strains is associated with sucrose-dependent cell-cell adhesion and the gtfC level of glucosyltransferases in the biofilm. Therefore, it is suggested that L. pentosus 13-4 and L. crispatus BCRC 14618 may contribute to preventing dental caries, as they showed an inhibitory effect on the growth and biofilm formation of the cariogenic bacterium S. mutans in vitro.
Keywords: Streptococcus mutans; biofilm; dental caries; glucosyltransferases (Gtfs); lactic acid bacteria (LAB).