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Foreign-body-associated experimental osteomyelitis induced with Bacteroides fragilis and Staphylococcus epidermidis
D W Lambe1, K P Ferguson, K J Mayberry-Carson
1Department of Microbiology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City 37614.
Abstract:
Bacteroides fragilis and Staphylococcus epidermidis, alone and in combination, were used to induce foreign-body-associated osteomyelitis in a rabbit model. In this model, a catheter, used as a foreign body, was implanted into the medullary cavity of the tibia. Only two of five animals infected with S. epidermidis alone developed culture-positive osteomyelitis, whereas all three animals infected with B. fragilis alone developed osteomyelitis. All six animals infected with both microorganisms developed culture-positive osteomyelitis. Roentgenographic and histologic evaluations confirmed the diagnosis of osteomyelitis. Transmission and scanning electron microscopy showed that when the two microorganisms are involved in a mixed infection, S. epidermidis predominates on the foreign body and B. fragilis predominates in the infected bone and marrow.
Insights
Foreign-body-associated osteomyelitis is more severe when caused by Bacteroides fragilis alone or in combination with Staphylococcus epidermidis. Mixed infections show distinct microbial distribution within the bone and foreign body.
Area of Science:
- Microbiology
- Infectious Diseases
- Orthopedic Surgery
Background:
- Foreign-body-associated osteomyelitis (FBAO) poses significant clinical challenges.
- Understanding polymicrobial infections is crucial for effective treatment.
Purpose of the Study:
- To investigate the role of Bacteroides fragilis and Staphylococcus epidermidis in a rabbit model of FBAO.
- To characterize the microbial distribution in monomicrobial versus polymicrobial infections.
Main Methods:
- Induction of FBAO in rabbits using a tibial implant.
- Infection with B. fragilis and S. epidermidis, alone and in combination.
- Roentgenographic, histologic, and electron microscopy evaluations.
Main Results:
- B. fragilis monoinfection led to a higher incidence of osteomyelitis than S. epidermidis monoinfection.
- All polymicrobial infections resulted in culture-positive osteomyelitis.
- S. epidermidis predominantly colonized the foreign body, while B. fragilis predominated in bone and marrow.
Conclusions:
- B. fragilis is a potent pathogen in FBAO.
- Mixed infections with B. fragilis and S. epidermidis are consistently established and show differential microbial localization.