Species identification of non-tuberculous Mycobacteria from patients with pulmonary infection in Hainan

  Objective   To identify the non-tuberculous Mycobacteria (NTM) detected in patients with pulmonary infection and discuss the types and population distribution of NTM pulmonary infection in Hainan province.

  Methods   The respiratory tract samples of the patients with suspected pulmonary tuberculosis who visited the Second Affiliated Hospital of Hainan Medical College from July 2016 to June 2021 were collected for Mycobacteria culture, and the culture-positive samples were preliminarily identified by P-Nitrobenzoic acid (PNB)/2-Thiophenecarboxylic acid hydrazide (TCH) culture using DNA microarrays. Microarray technology was used to identify Mycobacterium species, and gene sequencing was used to further identify strains that could not be identified.

  Results   A total of 8 507 respiratory tract samples from suspected pulmonary tuberculosis patients were collected during the study period. After excluding duplicated cases, 318 cases were preliminarily identified as NTM infection by PNB/TCH culture, and 315 cases were identified as NTM infection by DNA microarray chip technology and heat shock proteins 65 (hsp65) gene sequencing. Among them, 308 patients had a single infection pattern, 6 had MTB+NTM infection and 1 had a mixed infection of two different NTMs. There were 128 strains of rapidly growing Mycobacteria (RGM), accounting for 40.5%, mainly Mycobacterium chelonae/abscessus (32.9%); and 188 strains of slow growing Mycobacteria (SGM), accounting for 59.5%, with Mycobacterium intracellulare as the main strain (39.6%). More infection occurred in women than in men, especiadlly in middle-aged and elderly women, the male-to-female ratio of the cases was 0.79∶1. The difference in age distribution of the cases between men and women was significant (Z=2.200, P<0.05), and 91.1% of the cases were older than 40 years old.

  Conclusion   In Hainan, NTM pulmonary infection was mainly caused by Mycobacterium chelonae/abscessus and Mycobacterium intracellulare, and the middle-aged and elderly women aged ＞40 years were the main populations affected by NTM.