Methicillin-resistant Staphylococcus aureus osteomyelitis

Abstract

In five patients, the diagnosis of methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis was made by clinical and roentgenographic methods and confirmed by bone biopsy cultures. The treatment was staged according to the anatomic setting of the infection and the systemic and local competence of the host. Seven episodes of osteomyelitis were encountered in the five patients. Two patients had persistence of their infection and were successfully treated by additional surgical debridement, antibiotics, and adjunctive hyperbaric oxygen. Vancomycin was administered to all patients. The daily dosage of vancomycin ranged between 100 mg and 2.0 gm. The length of vancomycin therapy ranged from 19 to 56 days. Five of seven biopsy specimens grew bacterial organisms in addition to MRSA. The MIC of vancomycin for MRSA ranged between 0.39 and 1.56 micrograms/ml. Osteomyelitis was arrested in five of seven episodes, and follow-up evaluations ranged from two to 35 months. Two of five (40%) patients receiving the combination of vancomycin and tobramycin developed signs of renal toxicity. Renal function returned to normal after discontinuation of the antibiotics. MRSA osteomyelitis is usually acquired by spread from a contiguous focus of infection and is often polymicrobic in nature. Treatment with vancomycin or vancomycin plus tobramycin when the infection was polymicrobic was effective. The combination of vancomycin plus tobramycin is potentially nephrotoxic.