Mycobacterium simiae: a possible emerging pathogen in Iran.

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Mycobacterium simiae is a recognized pathogen causing pulmonary and disseminated infections globally, particularly in the Middle East.
• Nontuberculous mycobacteria (NTM) infections, including those caused by M. simiae, pose a significant challenge, especially in immunocompromised patient populations.
• Accurate identification of mycobacterial species is critical for effective treatment, particularly in patients with suspected tuberculosis who do not respond to standard therapy.

Purpose of the Study:

• To molecularly detect Mycobacterium simiae in patients suspected of tuberculosis in Iran.
• To evaluate the prevalence of M. simiae in various clinical samples.
• To assess the utility of molecular methods for identifying NTM infections.

Main Methods:

• Phenotypic identification of 117 mycobacterial isolates.
• Gene sequencing of 16S rRNA, rpoB, hsp65, and ITS regions for species identification.
• Analysis of clinical samples including bronchoalveolar lavage, sputum, blood, and lymph node biopsies.

Main Results:

• Twelve isolates (10.2%) of Mycobacterium simiae were identified from 117 mycobacterial isolates.
• M. simiae was detected in bronchoalveolar lavage, sputum, blood, and lymph node biopsy samples.
• Twenty-five percent (3/12) of M. simiae isolates were found in blood samples from HIV-positive patients with CD4(+) counts below 50/μl.

Conclusions:

• Molecular methods are essential for the accurate and rapid detection of Mycobacterium simiae.
• M. simiae is an important NTM to consider in the differential diagnosis of tuberculosis, especially in immunocompromised patients.
• Early and precise identification of NTM infections using molecular techniques can improve treatment outcomes for non-responding patients.