Analysis of the types and characteristics of non-tuberculous mycobacteria in high endemic areas of tuberculosis

Abstract

Objective: To understand the epidemiological, demographic and clinical characteristics of non-tuberculous mycobacterial lung disease (NTM-PD) in areas with high incidence of tuberculosis. Methods: A prospective surveillance study was conducted for non-tuberculous mycobacterial(NTM) at the Affiliated Hospital of Zunyi Medical University for five consecutive years. A total of 6259 culture-positive specimens grown on Roche medium between January 2017 and December 2021 were collected. After acid-fast staining, colony morphology, growth time, and p-nitrobenzoic acid detection, suspicious NTM strains were screened and identified by gene sequencing, and the dominant groups were subjected to drug sensitivity test. Results: A total of 107 suspected NTM colonies were screened from 6259 positive cultures, including 51 cases of NTM, 13 cases of MTB, and 43 cases of other bacteria. Among the 51 NTM positive patients, 43.1% were 45-65 years old. All the NTM positive specimens were derived from the respiratory tract. In 2017-2021, the isolation rate of NTM was the highest (1.18%) and the lowest (0.77%), and the main bacterial type was Mycobacterium abscessus (33.33%), followed by Mycobacterium intracellulare (27.45%), Mycobacterium chelates (11.76%), Mycobacterium kansasii (9.80%), Mycobacterium avium (7.84%), Mycobacterium gordonae (3.92%), Mycobacterium smegmatis (3.92%), and Mycobacterium bradyxanthum (1.96%). Other bacteria were dominated by Gordonia spp. The dominant NTM bacteria were Mycobacterium abscessus and Mycobacterium intracellulare, which had a high drug resistance rate. Middle-aged, male, bronchiectasis and serum albumin < 3.5 g/L were risk factors for NTM-PD. Conclusions: The trend of NTM infection rate is stable in this area, but the drug resistance rate is high. M. abscessus is the most common pathogen of NTM. Middle-aged, male patients with bronchiectasis and serum albumin < 3.5 g/L have a high risk of progressing to NTM-PD. In areas with a high incidence of TB, clinicians should make a differential diagnosis between suspected pulmonary TB and NTM infections.