Synergy of HBO2 and a local antibiotic carrier for experimental osteomyelitis due to Staphylococcus aureus in rats.

A standard rat model of Staphylococcus aureus-induced osteomyelitis was used to compare the effect of HBO2, a local antibiotic carrier (gentamicin-containing collagen sponge) and the combination of HBO2 with a local antibiotic carrier. For the induction of osteomyelitis, a defined Staphylococcus aureus suspension was inoculated into the medullary cavity. Arachidonic acid was used as sclerosing agent. With that procedure an infection rate of more than 95 percent was attained. Prior to the treatment interval surgical debridement of the soft-tissue infection was performed. In the control group the extent of infection was 4.9 x 10(6) CFU x g(-1) of tibial bone three weeks following implantation of organisms. Subsequent to debridement of the soft tissue infection, the bone infection decreased slightly with a value of 3.7 x 10(6) CFU x g(-1) of tibial bone at the end of the experiment. HBO2 as single-agent therapeutic reduced the infection to 1.7 x 10(5) CFU x g(-1) of tibial bone. Due to its high local antibiotic level, the gentamicin-collagen sponge achieved a reduction in organisms to 1.4 x 10(2) CFU x g(-1) of tibial bone. The effect was most marked using a 4-wk combination therapy with local application of the gentamicin-containing sponge and additional treatment with HBO2. In 9 of 11 animals, bacteria were no longer detectable in the processed bone substance. Each of the treatment modalities resulted in a significant therapeutic effect. No complete healing of the infection was achieved with the flexible collagen sponge characterized by pronounced and rapid release of gentamicin. In combination with hyperbaric oxygen an additive effect was attained and thus a significant improvement of treatment.