Genotyping and drug susceptibility testing of Mycobacterium tuberculosis in Iran: a multi-centre study

Tuberculosis (TB) is a deadly infection and caused 1.4 million deaths in 2018. Assessing the geographic distribution of major lineages of Mycobacterium tuberculosis can contribute greatly to TB control. Mycobacterial interspersed repetitive unit variable number tandem repeat (MIRU-VNTR) typing is commonly used to differentiate various lineages of M. tuberculosis. A total of 2747 clinical specimens were collected consecutively from October 2018 through June 2019. Clinical isolates were identified as M. tuberculosis using standard biochemical tests. The standard 15-locus MIRU-VNTR typing was used for the genotyping of clinical isolates. Drug susceptibility testing was performed using the conventional proportion method. From the collected specimens, 100 were culture positive for M. tuberculosis. Using MIRU-VNTR, 99 different patterns were detected among the 100 isolates. They were distributed in one cluster comprising two strains and 98 unique patterns. Most of our isolates were similar to New-1 and Delhi/CAS strains. Of the M. tuberculosis isolates, 83 (83.0%) were pan-susceptible and 17 (17.0%) were resistant to at least one drug. Our study showed that MIRU-VNTR is a useful method for studying the genetic diversity of M. tuberculosis isolates in different regional settings and will help the health authorities to construct a preventive programme for TB.