Antibiotic Resistance of Anaerobic Periodontal Pathogens to Tinidazole Versus Metronidazole.

Objectives: Tinidazole is a second-generation 2-methyl-5-nitroimidazole antibiotic similar to metronidazole, but with pharmacokinetic properties enabling only a once-a-day oral drug dose. This study determined the occurrence of in vitro resistance of selected anaerobic red/orange complex periodontal pathogens to tinidazole, metronidazole, and three other antibiotics.
Methods: Subgingival biofilm specimens from 31 adults with severe periodontitis were inoculated onto enriched Brucella blood agar plates with either no antimicrobials added, or supplemented with either tinidazole (16 mg/L), metronidazole (16 mg/L), doxycycline (4 mg/L), amoxicillin (8 mg/L), or clindamycin (4 mg/L), which represent CLSI or French Society for Microbiology (for doxycycline) non-susceptible/resistant breakpoint concentrations against anaerobic bacteria. After anaerobic incubation for 7 days at 37°C, selected anaerobic red/orange complex periodontal pathogens were identified with established phenotypic criteria, including Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia/nigrescens, Parvimonas micra and Fusobacterium nucleatum. In vitro antibiotic resistance was present with test periodontal pathogen growth on antibiotic-supplemented plates.
Results: Tinidazole and metronidazole inhibited in vitro growth of all test anaerobic red/orange complex periodontal pathogens in all study patient subgingival specimens, except for a tinidazole-resistant strain of P. intermedia/nigrescens from one patient that was additionally resistant in vitro to doxycycline, amoxicillin and clindamycin. Significantly greater mean total proportions of test anaerobic red/orange complex periodontal pathogens per patient were resistant in vitro to either doxycycline (6.4%), amoxicillin (5.6%), or clindamycin (9.5%), as compared to tinidazole (0.2%) or metronidazole (0%).
Conclusions: Tinidazole performed in vitro similar to metronidazole, and significantly better than doxycycline, amoxicillin, or clindamycin, against anaerobic red/orange complex periodontal pathogens. As a result of its similar antimicrobial spectrum, and once-a-day oral drug dosing, tinidazole may be considered in place of metronidazole for systemic periodontitis drug therapy where patient compliance with a multiple drug dose/day schedule is anticipated to be poor or difficult to attain.