INHIBITION OF BIOFILM FORMATION AND QUORUM SENSING- CONTROLLED VIRULENCE FACTORS OF CARIOGENIC ORAL PATHOGEN STREPTOCOCCUS MUTANS BY 4-HYDROXY-3-METHOXYBENZALDEHYDE

Abstract

Intro: Streptococcus mutans are considered to be the primary etiologic agents of dental caries and it is one of the major public health problems worldwide. The production of virulence traits that are regulated through a Quorum Sensing system confers resistance to antibiotics. This includes exopolysaccharide (EPS) production, acidurity and acidogenicity and biofilm formation. Methods: The antibiofilm activity of 4-hydroxy-3-methoxybenzaldehyde (4-H-3- MB) was evaluated against the S. mutans UA159 (control strain) and clinical isolate of S. mutans isolated from patients with dental caries. The 4-H-3-MB (Sigma-Aldrich, USA) was procured from commercial sources. Crystal violet staining assay was performed to assess antibiofilm activity. Bacterial growth curve analysis, quantification of EPS and inhibition of acid production were performed. The ADME properties of the compound were predicted using Molinspiration tool. Molecular docking was performed using glucan binding protein, glucansucrase and antigen I/II active site of S. mutans as proteins and 4- H-3-MB as ligand using Autodock Program. Findings: The compound 4-H-3-MB showed antibiofilm activity on S. mutans UA159 at low concentrations of 0.2, 0.1, 0.05 mg/ml (79.81%, 67.76% and 56.31% respectively) compared to the clinical strain (77.00%, 59.48% and 48.22% respectively). The 4-H-3-MB inhibited the EPS production and acid production on S. mutans UA159 and clinical isolates of S. mutans in a dose- dependent manner. The microscopic imaging revealed a dramatic reduction in the treated biofilm group as compared to the control. The 4-H-3-MB did not show any growth inhibition even at concentrations of 0.2–0.05 mg/ml. However, the 4- H-3-MB significantly reduced the biofilm thickness of both the control and the clinical strain. Autodock showed the lowest binding energy (-6.12 kcal/mol) with glucansucrase with six hydrogen bonds followed by GPBC (-5.32 kcal/mol) and antigen I/II (-4.87 kcal/mol). Conclusion: The present study indicates the potent anti-biofilm activity of 4-H- 3-MB compound for potential use against S. mutans.