Osteomyelitis Caused by Mycobacterium fortuitum-a Case Report

Non-tuberculous rapidly growing mycobacteria have been known to cause a variety of skin and soft tissue infection. The diagnosis of NTM in bone and joint infections is easily missed because of non-specific signs and symptoms. We report a case of a 65 year old male with osteomyelitis of the right knee of 4 years duration. The patient had no prior history of trauma or injury and finally presented with discharging sinus and edema of the right knee. The discharge persisted in spite of empiric therapy with anti-tubercular therapy. Rapidly growing Mycobacteria was isolated from the exudate which was identified as Mycobacterium fortuitum based on biochemical analysis. The isolate was found to be susceptible to Clarithromycin, Clindamycin, Gentamicin, Amikacin, Tetracycline, Co-trimoxazole and Imipenem The patient responded to medical therapy by oral Clarithromycin. An accurate diagnosis and effective treatment of an atypical mycobacteria infection of the musculoskeletal system is therefore mandatory to prevent severe bone and joint destruction. With non-specificity of imaging findings and clinical symptoms and signs, culture of mycobacteria becomes crucial in establishing the diagnosis.