Osteomyelitis experimentally induced with Bacteroides thetaiotaomicron and Staphylococcus epidermidis. Influence of a foreign-body implant.

Experimental osteomyelitis was induced in the rabbit tibia with Staphylococcus epidermidis alone, with Bacteroides thetaiotaomicron alone, and with both bacteria as etiologic agents, in the presence or absence of a foreign-body implant. Animals were monitored by clinical observation and roentgenographic, microbiologic, histologic, immunofluorescent microscopic, and electron microscopic methods. Scanning and transmission electron microscopy showed masses of coccoid and rod-shaped bacteria embedded in a matrix of exopolysaccharide and adhered to bone, marrow, and the foreign-body implant (when present). Of the 58 rabbits receiving an implant, osteomyelitis developed in 48 (83%), and bacteria were recovered by culture from 56 (97%). Of the 31 animals without the implant, osteomyelitis developed in 18 (58%), but no bacteria were recovered by culture. Bacterial recovery appeared to be dependent on the presence of the implant. The rate of induction and the severity of osteomyelitis were enhanced by the presence of the foreign-body implant and by the polymicrobic infection.