Haarlem 3 is the predominant genotype family in multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis in the capital of Iran: A 5-year survey

• Haarlem 3 genotype was the predominant genotype among isolates from MDR-TB cases in this study.
• Haarlem 3 family was also predominant in pre-XDR and XDR strains.
• Four major spoligotype lineages, i.e. the Haarlem 3, Beijing, T and CAS families, constituted the strains studied.

The objective of this study was to further understand the genetic diversity of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis isolates prevalent in Tehran, the capital city of Iran. From January 2010 to March 2015, a total of 723 M. tuberculosis strains were isolated from patients with pulmonary tuberculosis (TB). A total of 23 MDR, pre-XDR and XDR M. tuberculosis isolates were genotyped by spoligotyping and 24-loci mycobacterial interspersed repetitive unit–variable-number tandem repeat (MIRU-VNTR) typing. The results showed that the MDR, pre-XDR and XDR M. tuberculosis strains mainly belonged to the Haarlem 3 genotype (11/23; 47.8%), followed by the Beijing family (9/23; 39.1%). In addition, the 23 strains were clustered into 21 genotypes using a 24-loci MIRU-VNTR. In conclusion, Haarlem 3 genotype was the predominant genotype among the isolates from MDR-TB cases in this study, which could be of special concern.