Correlation Between Cell Surface Adhesins Genes and Biofilm Formation in Streptococcus Mutans Bacteria Isolated from Dental Caries

Abstract

Objectives: Streptococcus mutans (S. 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. The purpose of this study was to investigate correlation between cell surface adhesins genes and biofilm formation in Streptococcus mutans bacteria isolated from dental caries.Materials and Methods: Selective cultivation on mitis-salivarius-bacitracin (MSB) agar, biochemical tests and VITEK 2 system were carried out to isolate and identify S. mutans bacteria from 100 patients with dental caries. Identification of S. mutans isolates was confirmed by conventional PCR using specific pairs of PCR primers targeting Sm479 gene of S. mutans. PCR also were carried out to detect gbpA, gbpB, and spaP genes. Biofilm formation by S. mutans isolates was estimated using the microtiter plate crystal violet method. Results: A total of 42 S. mutans isolates were recovered from 100 clinical samples collected in the current study. There was a statistically significant difference in the biofilm formation ability among the isolates of S. mutans based (p < 0.05). Percentages of biofilm formation grade were 14.28% (6/42) strong biofilm producer, 35.71% (15/42) moderate biofilm producer, 28.57% (12/42) weak biofilm producer and 21.42% (9/42) non biofilm producer. Molecular detection of gbpA, gbpB and spaP genes was done for all S. mutans. The results showed that 80.95% (34/42), 85.71% (36/42) and 76.19% (32/42) of S. mutans isolates gave positive results for gbpA, gbpB and spaP and genes, respectively. The gbpA gene encodes glucan-binding protein (Gbp)A, the gbpB gene encodes GbpB, and the spaP gene encodes cell surface antigen, SpaP. Conclusion: It can be concluded that in the absence of only one of (gbpA, gbpB, spaP) genes, the biofilm will be weak, but in the absence of two or more of these genes, the biofilm will not form. Thus, each of these genes has own role in biofilm formation and specific relation to other genes responsible for biofilm formation of the bacterial isolates.