Antimicrobial Susceptibility of Streptococcus mutans Isolated from Dental Caries Patients: A Laboratory Study Using CLSI M100 Breakpoints

Abstract

Background: The prevalence of dental caries is one of the most common chronic infections, mostly associated with the cariogenic bacteria Streptococcus Mutans. There is an increase in the number of resistant strains, which poses a significant clinical problem. Objective: Isolation and identification of Streptococcus mutans from patients suffering from dental caries, analysis of resistance to five different clinically important antibiotics, and interpretation based on CLSI M100 criteria. Methods: Plaque specimens were collected from 80 participants. The isolates were then grown on Mitis Salivarius Agar and identified by conventional biochemical methods. Susceptibility to antimicrobials was determined through the Kirby-Bauer disc diffusion technique on Mueller-Hinton Agar containing 5% human blood (CLSI M100). The five antimicrobial agents tested were as follows: Penicillin, Ampicillin, Erythromycin, Tetracycline, and Vancomycin. Results: In 80 bacterial isolates, positive cultures were obtained for 50 samples, where 32 cultures of S. mutans had a frequency of 64%. All isolates were found to be sensitive to Vancomycin (100%) and Penicillin (87.5%). Resistance was observed against Erythromycin (21.9%) and Tetracycline (25%). Conclusion: Vancomycin maintains its effectiveness against S. mutans. Resistance to Erythromycin and Tetracycline needs further surveillance. Standardization of the CLSI method is essential in dental microbiology.