In Vitro Killing Activity of Crevicular Concentrations of Tinidazole Plus Common Oral Antibiotics Against High-Density Mixed Inocula of Periodontal Pathogens in Strict

Background: Odontogenic infections are polymicrobial. This study explores the in vitro killing activity by concentrations similar to those found in crevicular fluid of tinidazole in combination with amoxicillin/ clavulanic acid, clindamycin and levofloxacin against four groups of high-density mixed inocula of anaerobes (Prevotella buccae,Fusobacterium nucleatum, and Veillonella spp.) and facultative (Capnocytophaga spp. andStreptococcus spp.) isolates of periodontal pathogens. Methods: Killing curves were assessed under strict anaerobic conditions with antibiotics alone and in combination with tinidazole at concentrations similar to those achieved in crevicular fluid against ;10 7 colony forming units (CFU)/ml inoculum (1:1:1:1:1 proportion of the five bacterial isolates) of the four bacterial groups. Group 1 did not include b-lactamase–producing strains; groups 2, 3, and 4 included one, two, and three b-lactamase–producing strains, respectively. Results: In single-drug experiments, at 48 hours, tinidazole alone did not show significant killing of the entire bacterial population, whereas reductions in the initial inocula ‡2.09 log10 CFU/ml with clindamycin, ‡3.26 log10 CFU/ml with amoxicillin/clavulanic acid, and ‡3.83 log10 CFU/ml with levofloxacin were obtained. When combined with tinidazole, reductions were significantly higher for all antibiotics: ‡5.28 log10 CFU/ml with clindamycin, ‡4.78 log10 CFU/ml with amoxicillin/ clavulanic acid, and ‡6.17 log10 CFU/ml with levofloxacin. Conclusion: In addition to its high activity against anaerobic periodontal pathogens, tinidazole offered synergism with other antibiotics against the large strict anaerobic subpopulation and the small facultative subpopulation of a high-density mixed inocula of odontogenic pathogens under strict anaerobic conditions, similar to those of odontogenic infections. J Periodontol 2010;81:131-138.