Characteristics and comparison of rapidly growing and slowly growing nontuberculous mycobacterial pulmonary disease.

Background: Nontuberculous mycobacterial (NTM) pulmonary disease (PD) has rapidly increased globally. The characteristics and comparison of rapidly growing mycobacteria PD (RGM-PD) and slowly growing mycobacteria PD (SGM-PD) are still unclear.

Methods: Our study enrolled 31 NTM-PD patients. Clinical data, including baseline, symptoms, underlying disease, laboratory tests, metagenomic next-generation sequencing (mNGS) results, radiological images, treatment, and outcome were recorded and analyzed.

Results: Of the 31 patients with NTM-PD, 22 patients were female and 9 were male. It included 11 RGM-PD and 20 SGM-PD. There was no difference in age (P = 0.425) and body mass index (P = 0.152) between the two groups. The common respiratory diseases in prevalence included bronchiectasis and chronic obstructive pulmonary disease. Three patients had positive results of T-SPOT tuberculosis (TB), and none had positive Xpert-Mycobacterium tuberculosis/rifampin results. On admission, patients were symptomatic and included cough/sputum production, fever, weight loss, fatigue, and hemoptysis. In comparison to RGM-PD, patients with SGM-PD had a greater chance of experiencing fatigue (P = 0.012). No significance was found in serum biomarkers between RGM and SGM-PD, including CD4/CD8 ratio, white blood cells, neutrophils, lymphocytes, procalcitonin, ferritin, C-reactive protein, and erythrocyte sedimentation rate. No liver or kidney impairment was found. Patients with RGM-PD were more likely to have right lower lobe (RLL) impairment (P = 0.021) and a cavity characteristic (P = 0.012). All 31 cases had positive mNGS results. The duration of mNGS was shorter than conventional methods (3.4 ± 0.7 vs. 26.4 ± 20.9, P < 0.001).

Conclusions: Patients with SGM-PD were more likely to experience fatigue. The cavity and RLL involvement were more frequent in the RGM-PD. mNGS increases the identification of NTM specimens and complements the capabilities of conventional methods.