An outbreak of joint and cutaneous infections caused by non-tuberculous mycobacteria after corticosteroid injection

Summary Objectives An outbreak of joint and cutaneous infections among patients who had been injected at a single clinic in South Korea was investigated. Methods In this retrospective case–control study, 61 cases were diagnosed based on symptoms and signs of septic arthritis or cutaneous infection that developed after injections at the clinic between April and September 2012; 64 controls were investigated by administering questionnaires on risk factors and analyzing the clinic medical records. An environmental investigation was performed, and clinical specimens of the cases were analyzed by pulsed-field gel electrophoresis. Results All cases were injected with triamcinolone. A greater number of triamcinolone injections (adjusted odds ratio 4.3, 95% confidence interval 1.5–12.1 for six or more visits, compared with one or two visits) was associated with the development of an infection. In the clinic, only the triamcinolone injection was prepared by mixing with lidocaine and normal saline, and an alcohol swab was prepared using boiled tap water by members of the clinic staff. Although injected medications and environmental cultures were not found to be responsible, a single strain of Mycobacterium massiliense was isolated from the affected sites of 16 cases. Conclusions Repeated injection of triamcinolone contaminated with NTM from the clinic environment may have caused this post-injection outbreak.