Foreign-body-associated experimental osteomyelitis induced with Bacteroides fragilis and Staphylococcus epidermidis in rabbits.

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.