Epidemiology and clinical outcomes in skin and soft tissue nontuberculous mycobacteria infections: A retrospective study

Background: Nontuberculous mycobacteria (NTM) are emerging pathogens responsible for increasing skin and soft tissue infections (SSTIs) globally. However, the diagnosis and treatment of NTM SSTIs face significant challenges due to the lack of standardized guidelines. This study reviewed the clinical characteristics, diagnostic challenges, and treatment outcomes of NTM SSTIs in a large cohort from a tertiary referral center in Beijing, China.

Methods: We retrospectively reviewed 142 patients diagnosed with NTM SSTIs at a tertiary hospital from 2014 to 2023. Data collected included clinical presentation, microbiologic and histopathologic findings, diagnostic methods, treatment regimens, and outcomes. The patients were categorized based on NTM species, and immunocompromised status.

Results: The cohort included patients with various NTM species, with M. marinum, M. avium complex (MAC), and M. abscessus complex (MABC) being the most common. The number of patients with NTM infections increased annually (p < 0.01). Fifty-four patients (38.0 %) were immunocompromised. The likelihood of immunosuppression was significantly higher in the MAC group (90.0 %, p = 0.02) and M. kansasii group (80.0 %). The highest proportion of sporotrichosis-pattern lesions was observed in M. marinum infections (p = 0.03). MAC primarily caused extracutaneous disseminated infections (p = 0.05), and immunosuppressed patients were more likely to have extracutaneous infections (79.6 %, p = 0.01). Of the 41 disseminated infection cases, 17.1 % had prior pulmonary NTM infections later disseminated to the skin and had a significantly worse prognosis (p < 0.01). Most misdiagnosed cases (82.6 %) were initially considered skin tuberculosis and bacterial infections. Amikacin was the most consistently effective antibiotic, while resistance to cefoxitin and imipenem was common in MABC and M. chelonae. The MABC strains exhibited 40 % resistance to clarithromycin. Drug side effects occurred in 30.3 % of patients, with 8.5 % switching medications due to adverse impacts. The longest treatment duration was in M. kansasii cases (371.4 days, p = 0.03). Immunosuppressed patients received more drugs (Mean ± SD: 3.0 ± 0.9 vs 2.8 ± 0.7, p = 0.02), whereas showed a nonsignificant trend toward longer treatment durations.

Conclusions: The study highlighted significant challenges in differentiating NTM infections from other conditions and managing their diverse clinical manifestations. Enhanced diagnostic tools and standardized treatment guidelines are essential to improve patient outcomes and manage the increasing burden of NTM SSTIs.