Genetic Diversity and Prevalence of Nontuberculous Mycobacteria Isolated from Clinical Samples in Tehran, Iran.

The prevalence of nontuberculous mycobacteria (NTM) has increased in tuberculosis (TB)-suspected clinical samples. These bacteria are now recognized as important emerging pathogens, which affect both immunocompetent and immunocompromised individuals. The aim of this study was to evaluate the frequency of NTM in clinical samples and to efficacy of genomic loci as targets for detection of NTM species. This cross-sectional study was performed on 8166 clinical samples to determine the presence of NTM species from April 2013 to December 2015. The phenotypic methods were applied for preliminary NTM identification. The PCR-RFLP assay of heat shock protein-65 (hsp-65) gene and multilocus sequence analysis based on 16S-23S internal transcribes spacer (ITS), rpoB, and 16S rRNA genes were applied for species identification. In a total of 520 isolates from TB-suspected cases, 61 samples (11.7%) were identified as NTM. Overall, Mycobacterium (M.) fortuitum (63.9%) was the most frequently encountered species, followed by M. kansasii (9.8%), M. simiae (9.8%), M. abscessus (6.7%), M. gordonae (4.9%), M. flavescens (3.3%), and M. setense (1.6%). Moreover, sequencing of 16S rRNA and rpoB genes could identify all NTM species. In conclusion, we showed that the samples were infected by six NTM species, and M. fortuitum was the most frequent NTM strain. Based on the findings, 16S rRNA and rpoB genes were superior to ITS gene in identification of NTM species.

High rates of Mycobacterium fortuitum isolation in respiratory samples from Iranian patients with suspected tuberculosis: is it clinically important?

PURPOSE: Although Mycobacterium fortuitum (M. fortuitum) is not an organism rarely isolated from respiratory samples, its clinical importance is still not fully understood, which therefore prompted our current study. METHODOLOGY: We evaluated respiratory samples from 6800 patients with suspected tuberculosis from May 2014 to May 2016, for the detection of M. fortuitum using phenotypic and genotyping methods.Results/Key findings. Of the 40 patients with M. fortuitum lung disease, 35 had two or more positive culture results. The mean age of these 35 patients was 50.7±18.4 years, and 20 (57.1 %) were men. Sputum (68.6 %), haemoptysis (51.4 %), cough (45.7 %) and gastroesophageal disease (22.9 %) were the major presenting symptoms. Cystic fibrosis, other bacterial lung diseases and lung cancer were the main underlying pulmonary diseases. Five patients (12.5 %) were human immunodeficiency virus (HIV) positive. The most common chest X-ray findings were reticulonodular opacities (53.3 %). Multivariate logistic regression analysis revealed that cigarette smoking history (OR 0.334, 95 % CI 0.125-0.843, P=0.048) and underlying lung disease (OR 0.393, 95 % CI 0.216-0.588, P=0.023) were significant predictors for positive M. fortuitum infection. CONCLUSION: These results demonstrated the high frequency of M. fortuitum in respiratory samples and that this bacterium causes transient infection or colonization in patients with underlying pulmonary conditions, such as cystic fibrosis and cigarette smoking-induced. Additionally, it appears that infection with M. fortuitum is particularly common and may be important in patients with HIV.