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Efficacy of Metronidazole in experimental Bacteroides fragilis otitis media
Abstract:
The efficacy of metronidazole in otitis media due to Bacteroides fragilis was evaluated in a guinea pig model. Fifty-nine animals received an injection of 10(8) live B. fragilis bacteria through the tympanic membrane into the right middle ear cavity and metronidazole therapy was started 7 days later. On day 14 after challenge the animals were sacrificed and their middle ears analysed. Intraperitoneal injection of 6 mg metronidazole (about 20 mg per kg) once daily, 6 mg twice daily and 15 mg (50 mg per kg) once daily reduced the incidence of culture positive ears from 13/17 among untreated controls to 7/17 (p = 0.08), 3/10 (p = 0.05) and 2/15 (p = 0.001), respectively. The therapeutic efficacy of metronidazole in experimental otitis media was less than that expected from the concentrations of drug recorded in serum and the drug levels presumed to be achieved in the middle ear effusion.
Insights
Metronidazole showed efficacy in treating experimental otitis media caused by Bacteroides fragilis in guinea pigs. Higher doses and more frequent administration of metronidazole resulted in a greater reduction in bacterial ear infections.
Area of Science:
- Microbiology
- Pharmacology
- Otolaryngology
Background:
- Otitis media is a common infection, often involving anaerobic bacteria like Bacteroides fragilis.
- Metronidazole is a common antibiotic used to treat anaerobic infections.
Purpose of the Study:
- To evaluate the efficacy of metronidazole in treating experimental otitis media caused by Bacteroides fragilis in a guinea pig model.
- To determine the relationship between metronidazole dosage and therapeutic outcomes in this model.
Main Methods:
- A guinea pig model of otitis media was established by injecting Bacteroides fragilis into the middle ear cavity.
- Animals were treated with varying doses and frequencies of metronidazole starting seven days post-infection.
- Middle ear cultures were analyzed 14 days after bacterial challenge to assess treatment efficacy.
Main Results:
- Metronidazole treatment significantly reduced the incidence of culture-positive ears compared to untreated controls.
- Higher doses (50 mg/kg once daily) and twice-daily administration of metronidazole (20 mg/kg total daily dose) showed the most significant reduction in bacterial presence.
- Therapeutic efficacy appeared lower than expected based on serum drug concentrations and presumed middle ear fluid levels.
Conclusions:
- Metronidazole demonstrates efficacy against Bacteroides fragilis-induced otitis media in a guinea pig model.
- Dosage and frequency of metronidazole administration impact treatment outcomes.
- Further investigation is needed to understand the drug's penetration and efficacy within the middle ear environment.