Retrospective analysis of non-tuberculous mycobacterial skin infections: diagnostic accuracy, treatment efficacy, and PCR-based species detection in a Chinese primary care hospital.

Non-tuberculous mycobacterial (NTM) skin infections present diagnostic and therapeutic challenges in resource-limited primary care settings. This retrospective study evaluated the diagnosis and treatment of NTM skin infections at a primary care hospital in Shouguang City, a coastal region of China with high-risk occupational exposure to aquatic environments, from 2021 to 2022. We analyzed 144 patients, using real-time PCR on formalin-fixed paraffin-embedded (FFPE) tissue samples to validate empirical diagnoses based on clinical symptoms, exposure history, and histopathology. Our results demonstrated a high concordance (79.17%) between empirical and molecular diagnoses, confirming the reliability of the primary care hospital's diagnostic approach. Real-time PCR successfully identified specific NTM species in a subset of cases, with IMPORTANCE: This study addresses a critical gap in managing non-tuberculous mycobacterial (NTM) skin infections in resource-limited primary care settings, with particular relevance to coastal regions like Shouguang, where occupational exposure to marine environments elevates infection risk. By validating empirical diagnosis through molecular testing, we demonstrate that integrated clinical-histopathological assessment is a reliable method for identifying NTM infections where advanced diagnostics are unavailable. Our adaptation of real-time PCR to archived FFPE tissues provides a feasible model for retrospective species identification and research, overcoming key resource constraints. The high documented cure rate with clarithromycin-rifampicin regimens provides practical treatment benchmarks for regions with similar epidemiological profiles. These findings offer immediate clinical value by: (i) reinforcing the reliability of empirical diagnosis in resource-limited contexts, (ii) establishing a practical pathway for molecular confirmation using stored samples, and (iii) validating effective treatment protocols for high-risk occupational groups. As NTM incidence increases globally, this work equips primary care systems with evidence-based strategies to improve diagnostic accuracy and patient outcomes in settings with high marine exposure while simultaneously enabling future research through the utilization of existing biospecimen repositories.