Molecular Characterization ofIsolates From West of Iran Using Mycobacterial Interspersed Repetitive Unit-Variable Number Tandem Repeats: A Cross-Sectional Study.

BACKGROUND AND AIMS: Tuberculosis (TB) remains a major global health problem and poses significant challenges for diagnosis and treatment. The World Health Organization (WHO) recommends the use of molecular methods for the diagnosis and genotyping ofcomplex (MTBC). Mycobacterial interspersed repetitive unit-variable number tandem repeats (MIRU-VNTR) has proven to be a valuable method for studying the genetic diversity of(MTB). To the best of our knowledge, no previous study has investigated MTB diversity in Ilam, west of Iran. Therefore, this study aimed to investigate the genetic diversity ofisolates and the occurrence of rifampicin-resistant(RR-TB).

METHODS: In total, 643 suspected cases of TB were collected from March 2022 to November 2023. Acid-fast bacilli (AFB) were detected using Ziehl-Neelsen (ZN) staining, fluorochrome staining, and culture on Löwenstein-Jensen medium. GeneXpert MTB/RIF method was applied to detect MTB and RR-TB. Finally, 15-locus-based MIRU-VNTR was used for molecular genotyping.

RESULTS: Out of 643 specimens, 20/643 (3.11%) specimens were diagnosed as positive for MTB by culture. GeneXpert MTB/RIF confirmed RR-TB in one sample. Positive isolates were placed in nine different clusters using MIRU-VNTR genotyping. All isolates were not assignable to the sublineages in the MIRU-VNTRplus database but were close to the Delhi/CAS.

CONCLUSION: The high clustering rate in our results indicates that TB transmission in this region originates from multiple sources and reflects active transmission rather than reactivation of latent TB. In addition, the lineages of MTB isolates identified in Ilam were closely related to those reported from other Iranian provinces and neighboring countries, indicating epidemiological links. Improving diagnostic capacity and implementing effective control measures are essential to reduce TB transmission.