Antibacterial Efficacy of Local Therapeutic Agents Against Specific Gram-Positive Bacteria Associated with...

Background/Objectives: Pericoronitis is a polymicrobial, biofilm-associated odontogenic infection; however, selected facultative Gram-positive bacteria may contribute to oral infectious persistence. This study compared the residual antibacterial activity of chlorhexidine (CHX), low-level laser therapy (LLLT), injectable platelet-rich fibrin (i-PRF), and amoxicillin-loaded i-PRF against selected oral and odontogenic bacterial strains. Methods: Standardized planktonic suspensions of Streptococcus mutans ATCC 25175, Staphylococcus aureus ATCC 25923, and Enterococcus faecalis ATCC 29212 were prepared at 0.5 McFarland turbidity. Five conditions were evaluated: 0.2% CHX, i-PRF, amoxicillin-loaded i-PRF, 976 nm diode LLLT, and 0.9% sodium chloride as the negative control. Twelve independent tubes were used for each treatment and species, yielding 180 experimental units. After a residual 24-h exposure/incubation period, samples were serially diluted, plated on 5% sheep blood agar, and quantified as CFU/mL. Data were analyzed using non-parametric tests. Results: Significant treatment-dependent differences were observed for all species (p < 0.001). CHX showed the most consistent antibacterial activity, with median residual counts of 550 CFU/mL for S. mutans, 1 CFU/mL for S. aureus, and 5.5 CFU/mL for E. faecalis. i-PRF alone was comparable to the negative control. Amoxicillin-loaded i-PRF markedly reduced S. aureus counts, whereas S. mutans and E. faecalis remained at high residual levels. LLLT showed partial, variable inhibition mainly against S. aureus. Conclusions: CHX demonstrated the most consistent antibacterial effect in this planktonic residual 24-h in vitro model. i-PRF alone showed no measurable antibacterial activity, while amoxicillin-loaded i-PRF and LLLT exhibited limited, species-dependent effects.