Mycobacterium tuberculosis has infected more than two billion individuals worldwide, of whom 5%–10% have clinically active disease and 90%–95% remain in the latent stage with a reservoir of viable bacteria in the macrophages for extended periods of time. The tubercle bacilli at this stage are usually called dormant, non-viable, and/or non-culturable microorganisms. The patients with latent bacilli will not have clinical pictures and are not infectious. The infections in about 2%–23% of the patients with latent status become reactivated for various reasons such as cancer, human immunodeficiency virus infection, diabetes, and/or aging. Many studies have examined the mechanisms involved in the latent state of Mycobacterium and showed that latency modified the expression of many genes. Therefore, several mechanisms will change in this bacterium. Hence, this study aimed to briefly examine the genes involved in the latent state as well as the changes that are caused by Mycobacterium tuberculosis. The study also evaluated the relationship between the functions of these genes.

Objective: To investigate the prevalence of non-tuberculosis mycobacteria (NTM) among the samples deposited from the National Tuberculosis Reference Laboratory of Iran between 2011 and 2018. Methods: The study evaluated the prevalence of NTM among specimens from patients with pulmonary tuberculosis symptoms (n=15 771) deposited at the National Tuberculosis Reference Laboratory of Iran from 2011 to 2018. Detection of Mycobacterium (M.) tuberculosis was based on presence of a 190-bp amplicon from IS6110 insertion sequence using Tb1 and Tb2 primers, and amplicon-negative specimens were tested for NTM and M. tuberculosis (refractory to IS6110 amplification) using restriction fragment length polymorphism PCR of hsp65 amplicon fragment. Results: A total of 7 307 (46.33%) M. tuberculosis and 658 (4.17%) NTM specimens were found, the latter mainly comprising M. abscessus (10.18%), M. avium (2.28%), M. chelonae (8.97%), M. intracellulare (10.49%), M. kansasii (4.71%), and M. simiae (56.08%). Conclusions: As treatment for NTM differs from that for M. tuberculosis, accurate detection of Mycobacterium sp. is of public health significance.