Abstract
Background: The global incidence of rapidly growing mycobacterial (RGM) infections is rising. We examined cases of extrapulmonary RGM infection in Far North Queensland (FNQ), tropical Australia, to characterise their presentation and the challenges in their management. Methods: All RGM isolated from extrapulmonary sites in FNQ residents between January 2008 and December 2024 were identified; the isolates’ microbiological characteristics and the patients’ clinical course were reviewed. Results: Mycobacterium fortuitum group (51/144, 35%), Mycobacterium abscessus complex (45/144, 31%) and Mycobacterium chelonae (30/144, 21%) were the most frequently isolated RGM. Clinical infection was confirmed in 103/144 (72%) isolates. The annual incidence of RGM clinical infections increased over the study period from 0.4 to 2.4/100,000 population (rs=0.57, p=0.02). Patients had a median (interquartile range (IQR)) age of 52 (33-66) years; 10/103 (10%) were immunosuppressed while only 6/103 (6%) had other significant comorbidity. Preceding environmental trauma was documented in 39/103 (38%), 38/103 (37%) followed surgery and 23/103 (22%) infections involved prosthetic material. The median (IQR) duration of symptoms at diagnosis was 5 (2-12) weeks. Antimicrobial susceptibility testing demonstrated high rates of resistance; 78 patients were treated with antibiotics for a median (IQR) duration of 18 (16-24) weeks with 47/78 (60%) experiencing an adverse drug reaction. Surgical management was necessary in 64/103 (62%). There were 6 microbiologically-confirmed relapses but no deaths directly attributable to the infection or its treatment. Conclusion: Extrapulmonary RGM infections are increasing in frequency in tropical Australia and predominantly affect younger, healthy individuals. Delayed diagnosis and adverse events from antimicrobial therapy are common.