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Anaerobic osteomyelitis--treatment with metronidazole in an experimental rabbit model
A Johansson1, G Eliasson, O Svensson
1Department of Orthopaedic Surgery, Huddinge University Hospital, Sweden.
Abstract:
Anaerobic micro-organisms are important agents in chronic bone infections. Their pathogenic role, however, is still unclear partly because of methodological reasons. In this paper an experimental model of osteomyelitis is used for studies of metronidazole treatment of bone infections induced by Bacteroides fragilis. The proximal tibial metaphyses of ten New Zealand white rabbits were excavated and filled with sheets of polyvinyl alcohol, into which a suspension of B. fragilis cells was injected on the right side, while saline was used on the left side. Within a month the animals showed immunological and radiological signs of an established bone infection. After 25 weeks of observation, four animals were treated with subcutaneous injections of metronidazole at a dosage of 10 mg/kg body weight twice daily for three weeks and five animals received saline. After 37 weeks the animals were killed. Radiological, histological and microbiological evaluation showed bilateral osteomyelitis in all animals. Prolonged raised titres of antibodies suggested an established infection, and not merely a colonization. There were no differences between the animals treated with metronidazole and the animals not treated.
Insights
Metronidazole treatment did not resolve chronic bone infections caused by Bacteroides fragilis in rabbits. This study highlights challenges in treating anaerobic osteomyelitis, even with antimicrobial therapy.
Area of Science:
- Microbiology
- Orthopedics
- Pharmacology
Background:
- Anaerobic bacteria are implicated in chronic bone infections.
- The pathogenic role of anaerobic microorganisms in osteomyelitis remains unclear due to methodological challenges.
Purpose of the Study:
- To investigate the efficacy of metronidazole in treating experimental osteomyelitis induced by Bacteroides fragilis in a rabbit model.
- To evaluate the impact of metronidazole on established anaerobic bone infections.
Main Methods:
- An experimental osteomyelitis model was established in New Zealand white rabbits by infecting the proximal tibia with Bacteroides fragilis.
- Animals were treated with metronidazole or saline after infection was established.
- Radiological, histological, and microbiological evaluations were performed to assess infection and treatment outcomes.
Main Results:
- Bilateral osteomyelitis was confirmed in all animals, regardless of treatment.
- Prolonged elevated antibody titers indicated established infections rather than mere colonization.
- No significant differences in infection resolution were observed between metronidazole-treated and saline-treated groups.
Conclusions:
- Metronidazole was ineffective in treating chronic osteomyelitis induced by Bacteroides fragilis in this experimental model.
- The findings suggest limitations in using metronidazole for established anaerobic bone infections.
- Further research is needed to develop effective therapeutic strategies for anaerobic osteomyelitis.