Virulence traits-based behavior of Streptococcus mutans bacteria from dental plaque and dental caries conditions

Abstract

Streptococcus mutans has significant virulence factors associated with the etiology and pathophysiology of dental plaque and caries through adherence to the tooth surface and biofilm formation. These microbes can tolerate and survive the acidic environment. The study aimed to compare the behavior of the S. mutans isolates from dental plaque and caries conditions, in addition to the evaluation of the biofilm formation by S. mutans with oral microbiota (Candida albicans). A total of 106 S. mutans isolates were recovered including 56 isolates from soft caries lesions, 30 isolates from the plaque of caries active and 20 isolates from the plaque of caries- free samples. The isolates' virulence efficacy was assessed phenotypically by acid production, acid tolerance, and biofilm formation assays. PCR detected genes encoding these virulence traits. There was a significant difference (p < 0.05) between the three groups of isolates in biofilm formation, biofilm formation when co-cultivated with C. albicans, pH reduction by acid production, but there was no significant difference in withstanding acidic pH. S. mutans isolates harbored the genes glucosyltransferase B (gtfB), glucan binding protein B (gbpB), F1F0 membrane-bound proton-translocating ATPase C subunit (atpH) and lactate dehydrogenase (ldh) which are responsible for biofilm formation, sucrose- dependent adhesion, acid tolerance and acid production, respectively. In conclusion, S. mutans isolates from caries-free and caries active dental plaque and dental caries conditions showed different virulence efficacy-based behaviour. C. albicans enhances the biofilm formation by S. mutans. Further investigation of factors influencing variable behavior of S. mutans bacteria from different lesions is warranted.