Non-tuberculous mycobacteria (NTM)—previously considered as saprophytic organisms—are now increasingly recognized as human pathogens [1, 2]. Although humans are routinely exposed to NTM, clinical infection rates are low; further, these infections typically occur in immunocompromised patients. However, an increasing incidence of NTM infections in immunocompetent hosts—caused by direct inoculation, such as contamination from surgical procedures or penetrating trauma—has been noted [1]. Clinically and histopathologically, musculoskeletal infections caused by NTM resemble those caused by Mycobacteria tuberculosis; however, they are largely resistant to routine anti-tuberculosis agents [3,4]. Therefore, NTM infections can either be missed or even regarded as drug resistant tuberculosis, causing a significant delay in diagnosis. Here, we present the features and outcomes of 6 immunocompetent patients with musculoskeletal infections caused by NTM.

We retrospectively analyzed the outcomes of musculoskeletal infections caused by NTM in 6 healthy, immunocompetent hosts admitted between 2004 and 2015. The etiology was traced, and available culture reports were reviewed.

NTM inoculation was traced to open fractures in 2 patients (1, patella; 1, humerus), intra-articular injection in 2 patients (1, hip; 1, shoulder), local steroid injection to the calcaneum in 1 patient, and an arthroscopic procedure in the knee joint in 1 patient. Histopathological analyses revealed chronic granulomatous inflammation, with positive NTM cultures. Following radical debridement and targeted antibiotic therapy for NTM, all 6 patients showed complete resolution over a follow-up period of 8 months to 10 years, with no recurrence.

NTM are an uncommon pathogen in immunocompetent patients. In patients with chronic granulomatous infection not responding to standard anti-tuberculous treatment and with a history suggestive of inoculation—namely open fractures, surgical intervention, or injection—the possibility of NTM infection should be considered. Appropriate antibiotic therapy based on drug susceptibility reports gives good outcomes. While the hallmark of M. tuberculosis infections is chronic granulomatous inflammation, not every case of mycobacterial granulomatous inflammation is due to M. tuberculosis.