Prevalence and Antimicrobial Susceptibility of Non-tuberculous Mycobacteria Isolated from Sputum Samples of Patients with Pulmonary Infections in China

Non-tuberculous mycobacteria (NTM) are widely associated with pulmonary diseases. Evidence is lacking on the transmission of NTM from one person to another. Hence, it has gained lower public health priority than tuberculosis.

We determined the prevalence and antibiotic resistance rate of NTM isolated from sputum samples of patients with pulmonary infections.

A total of 375 duplicate sputum samples were collected from 375 patients on consecutive days. The NTM growth was assessed using BACTEC 960 mycobacterial growth indicator tubes. The GenoType Mycobacterium CM/AS line probe assay was used for the species-level identification of mycobacteria. Antibiotic susceptibility tests were performed using the auto-MODS assay.

The overall NTM prevalence rate was 34.4%. Mycobacterium avium complex (24.8%) was the predominant species identified, followed by M. kansasii(24%) and M. abscessus complex (20.2%). Of the 129 NTM isolates tested for antibiotic susceptibility, 62.8% were resistant to rifampicin, 60.5% to levofloxacin, 58.1% to ofloxacin, 55.8% to ethambutol, 49.6% to isoniazid, 48.1% to streptomycin, and 41.9% to amikacin. Seventy-three (56.6%) isolates were identified as multidrug-resistant (MDR) isolates.

Mycobacterium avium complex was the predominant species identified, and the majority of the organisms were resistant to commonly used anti-tuberculosis drugs. The high prevalence of NTM and drug resistance towards the tested antibiotics suggests that NTM can no more be ignored as a contaminant, reiterating the need for periodic surveillance and species-specific treatment for effective management of diseases caused by NTM.