Clinical Characteristics, Molecular Diagnosis, and Drug Resistance Profiles of Nontuberculous Mycobacteria Infections: A Retrospective Analysis Using PCR Melting Curve Technology.

Nontuberculous mycobacteria (NTM) are emerging global pathogens. This study aimed to analyze the clinical features, species distribution, and drug resistance profiles of NTM infections in a northern Chinese hospital. A retrospective cohort study included 1769 patients with suspected mycobacterial infection from August 2023 to July 2025. PCR melting curve analysis (PCR-MCA) was used for initial screening, with confirmation by targeted next-generation sequencing (tNGS). Confirmed cases were classified as localized or disseminated disease. Among 60 confirmed NTM cases, 48 were localized (mainly pulmonary) and 12 were disseminated. The predominant species in localized disease were Mycobacterium intracellulare (35.4%) and Mycobacterium abscessus (35.4%), while disseminated cases were primarily caused by M. intracellulare, Mycobacterium avium, and Mycobacterium kansasii. Localized disease presented mainly with cough and expectoration (95.8%), whereas fever was common in disseminated infections (83.3%, p < 0.001). Key risk factors included prior tuberculosis, bronchiectasis, and immunodeficiency. Time to diagnosis was significantly longer in localized cases (10.59 ± 17.05 months) than disseminated (1.83 ± 1.47 months). Drug resistance rates varied significantly among species. The M. avium complex (MAC) predominates in NTM disease. Species identification and drug susceptibility testing are essential for guiding targeted therapy due to non-specific symptoms and species-dependent resistance patterns.