Occurrence and risk factors of nontuberculous mycobacteria in tuberculosis-suspected patients in the north of Iran

Abstract

Background and Objectives: Some Nontuberculous Mycobacteria (NTM) can occasionally infect the human population and cause infections having symptoms similar to tuberculosis (TB). This study tried to provide updated data about the frequency and diversity of NTM species.
 Materials and Methods: Suspicious samples of Mycobacterium tuberculosis (MTB) with both positive results in Ziehl-Neelsen (ZN) staining and Löwenstein-Jensen medium culturing were evaluated during January 2016 and December 2018 in Gorgan, Iran. After determination of MTB isolates by the growth rate, pigmentation status, the niacin test, and the insertion sequence 6110 (IS6110) PCR assay, other unknown isolates (presumably NTM) were detected by the 16S rDNA sequencing method and drawing the phylogenetic tree. Based on the patients’ demographic information, their risk factors were also assessed.
 Results: Among 226 culture-positive samples, obtained from 2994 individuals with suspected symptoms of TB, the analyses found 12 (5.3%) NTM and three Mycobacterium caprae isolates. Mycobacterium simiae (6/12) was the most prevalent NTM species. The average nucleotide similarity value was 98.2% ± 3.7. In comparison to patients with MTB (211 confirmed cases), other mycobacterium infections were more common in patients over 65 years old (Odd ratio (95% convenience interval): 2.96 (0.69 - 12.59), P = 0.14).
 Conclusion: Although the NTM species has a small portion in TB suspected patients, their prevalence has increased, mainly in elderly patients. Moreover, M. simiae was the most prevalent NTM species in our region. Therefore, identification of common species in each region is recommended and clinicians should pay more attention to them in each region.

Molecular epidemiology of nontuberculous mycobacteria isolated from tuberculosis-suspected patients

“…As a result of the development of molecular methods for detecting NTM infections causality, such as 16SrDNA sequencing, the reporting rate of NTM infections has gone up in such areas. A lack of laboratory facilities and misdiagnosis may be the cause of this issue in many economically challenged countries (Nasiri et al 2015;Shafipour et al 2021). There is still a challenge to detect NTM infections among tuberculosis (TB) suspected samples and to control them in some of these developing countries like Iran.…”