Assessment of the Antimicrobial Activity of a Triple Antibiotic Gel Against Periodontal Pathogens

Introduction: Periodontal disease is a biofilm-mediated infection primarily caused by pathogens such as Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia. As antibiotic resistance continues to pose a challenge, localized drug delivery systems like triple antibiotic gels have gained interest for their targeted antimicrobial effects. Determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of such formulations is essential to assess their efficacy against key periodontal pathogens and to guide clinical application. Methods: The triple antibiotic gel, composed of metronidazole, ciprofloxacin, and minocycline, was tested in vitro using the broth microdilution method to determine MIC and MBC values. Standardized bacterial strains were incubated with serial dilutions of the gel under anaerobic conditions appropriate for each species. MIC was recorded as the lowest concentration inhibiting visible bacterial growth, while MBC was defined as the lowest concentration resulting in ≥99.9% bacterial kill. Results: The triple antibiotic gel demonstrated strong antibacterial activity against all tested strains. MIC and MBC values were lowest for A. actinomycetemcomitans, followed by P. gingivalis and P. intermedia, indicating differential susceptibility. All MIC and MBC values fell within clinically relevant concentrations. Conclusion: The triple antibiotic gel exhibits potent in vitro antimicrobial activity against key periodontal pathogens, supporting its potential as an adjunctive local therapy in periodontal treatment. Further in vivo studies are recommended to confirm clinical efficacy..