Antibacterial and Anti-biofilm Effects of Chitosan Nanoparticles on Streptococcus Mutans Isolates

 Dental caries is an infectious disease caused by bacterial colonization and biofilm formation. Streptococcus mutans (S. mutans) is mainly responsible for dental caries development. Considering the side effects of synthetic antibacterial agents, attempts are ongoing to find antimicrobial agents with minimal or no side effects for preventing dental caries. Based on the reported antibacterial activity of chitosan, this in vitro study aimed to assess the antibacterial and anti-biofilm effects of chitosan nanoparticles on S. mutans clinical isolates. 

 S. mutans isolates were isolated from supragingival plaque and carious lesions of patients by standard biochemical tests and Polymerase Chain Reaction (PCR) of the gtfB gene. The antibacterial activity and Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) of chitosan nanoparticles against S. mutans was evaluated by the agar well-plate and broth micro-dilution test, respectively. Also, the effect of chitosan nanoparticles on biofilm formation was evaluated using micro-titer plate method. Data were analyzed using ANOVA.

 Fifteen S. mutans isolates were collected from patients. The chitosan nanoparticles synthesized had a diameter of 20–30 nm. The chitosan nanoparticles showed antibacterial activity against S. mutans isolates. MICs and MBCs ranged from 0.625-2.5 µg/ml and 1.25-5 µg/ml, respectively. All isolates evaluated in this study were biofilm-forming and 5 of these produced a strong biofilm. The chitosan nanoparticles inhibited biofilm formation at 0.75 µg/ml concentration. 

 Chitosan nanoparticles had antibacterial and anti-biofilm activity on S. mutans clinical isolates. This study suggests the potential of chitosan nanoparticles as antimicrobial agents against cariogenic Streptococci.