Clinical Presentations and Species Spectrum of Nontuberculous Mycobacteria in Suspected Pulmonary Tuberculosis Cases

The prevalence of nontuberculous mycobacteria (NTM) is on the rise worldwide. The diagnosis of NTM lung disease (NTM-LD) is a dilemma. The 2020 guidelines jointly established by the American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) outline the criteria for diagnosing pulmonary NTM disease. Herein, we report a series of cases with an analysis of relevant literature to gain insight into the pathogenicity of NTM species, the risk factors involved, and treatment strategies.

This is a prospective observational study starting from April 2023 to December 2023. A total of 370 suspected pulmonary tuberculosis (TB) patients were included. Clinical specimens were processed for Ziehl-Neelsen staining, GeneXpert Mycobacterium tuberculosis (MTB)/RIF assay, and culture. Culture-positive mycobacteria were classified as MTB complex or NTM based on detection of MPT64 antigen. The NTM isolates were speciated by line probe assay using GenoType^® Mycobacterium common mycobacteria (Hain Lifescience, Nehren, Germany). The criteria of ATS/IDSA were applied to confirm NTM-LD.

Nine (n = 9) patients were diagnosed as cases of NTM-LD. Bronchiectasis and previous TB were the most common comorbidities. Mycobacterium scrofulaceum (n = 2), Mycobacterium szulgai (n = 2), Mycobacterium intracellulare (n = 1), Mycobacterium kansasii (n = 1), Mycobacterium abscessus (n = 1), Mycobacterium fortuitum (n = 1), and Mycobacterium interjectum (n = 1) were the species involved. Specific therapeutic drug regimens were administered in four cases, which resulted in clinical improvement.

People with comorbid (LDs) are at risk of NTM-LD. The severity of NTM-LD and mortality also depend on the species involved. New guidelines with evidence-based recommendations should be formulated to simplify the diagnosis and treatment of NTM-LD caused by an array of more than 190 species.