Therapy with gentamicin-PMMA beads, gentamicin-collagen sponge, and cefazolin for experimental osteomyelitis due to Staphylococcus aureus in rats

INTRODUCTION

In spite of new surgical techniques and recently developed antibiotics, there is no satisfactory solution for the treatment of chronic posttraumatic osteomyelitis. The introduction of local antibiotic treatment with gentamicin-PMMA beads according to Klemm has provided new stimuli for the treatment of chronic osteomyelitis. With the development of collagen as an absorbable carrier substance, the disadvantages of the rigid carrier system became evident. Due to the varying surgical techniques and different forms of adjuvant therapy, it is difficult to assess therapeutic methods and compare different studies. Therefore, it seemed appropriate to study the effect of local treatment with different antibiotic carriers in the setting of an animal study.

MATERIALS AND METHODS

The proven rat model for Staphylococcus aureus-induced osteomyelitis was used to compare the results of monotherapy with cefazolin, gentamicin-PMMA beads, or gentamicin-containing collagen sponge with the combination of local and systemic antibiotic treatment.

RESULTS

Single-agent therapy with parenterally administered cefazolin reduced the CFU from 3.7 x 10(6) to 2.9 x 10(4) g(-1) of tibial bone. The effect on osteomyelitis was more pronounced with the local application of antibiotics. The best results were achieved with the gentamicin-containing collagen sponge which reduced the bacterial colony count to 1.4 x 10(2) CFU/g compared with 9.8 x 10(2) CFU/g achieved with gentamicin-PMMA beads. The effect was most marked using a 4-week combination therapy with local application of the gentamicin-containing collagen sponge and systemic administration of cefazolin. In 9 of 11 animals, no bacteria could be detected in the bone.

CONCLUSION

Each of the treatment modalities resulted in a significant therapeutic effect. Due to its ability to quickly release large amounts of gentamicin, the flexible gentamicin-containing collagen sponge proved to be superior to the rigid PMMA system. Although the gentamicin-containing collagen sponge provided high antibiotic concentration at the site of implantation, an additive effect was attained when combined with systemic antibiotic treatment.

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.

Therapy with hyperbaric oxygen and cefazolin for experimental osteomyelitis due to Staphylococcus aureus in rats

Hyperbaric oxygen (HBO2) is used as adjunctive therapy for chronic osteomyelitis, yet its efficacy remains controversial. A recently developed rat model for osteomyelitis due to Staphylococcus aureus was used to compare the results of treatment with HBO2, cefazolin, a combination of both, or no treatment. For the induction of tibial osteomyelitis, S. aureus was inoculated into the medullary cavity. Arachidonic acid was used as the sclerosing agent. With that procedure, an infection rate of 96% was attained. For long-term antibiotic treatment, a port system was developed and implanted. Hyperbaric treatment alone reduced the colony-forming units (CFU) from 2.9 x 10(6) to 6.2 x 10(5) x g(-1) of tibial bone. The effect on the infection was more pronounced with antibiotic therapy alone, 10.5 x 10(4) CFU per g of tibial bone were measured. However, changes were most marked using a 4-wk combination therapy consisting of HBO2 and an antibiotic agent. The colony count was 2.7 x 10(3) CFU. Each of the treatment modalities resulted in a significant therapeutic effect. The results not only demonstrated the effectiveness of HBO2 in the treatment of osteomyelitis, but revealed a potential additive effect with the combination of HBO2 and an antibiotic.