First insight into the genetic diversity of Mycobacterium tuberculosis strains from patients in Duhok, Iraq

Abstract Background The aim of this study was to evaluate the genotypic diversity of Mycobacterium tuberculosis strains using IS 6110 RFLP, spoligotyping and MIRU-VNTR typing. Materials and methods Between June 2008 and June 2009, all smear positive pulmonary specimens were collected prospectively at the national tuberculosis program (NTP) center of Duhok province. The specimens were processed for culture by modified Petroff’s method and were inoculated into two tubes of Löwenstein-Jensen (LJ) media. The isolates were identified as M. tuberculosis by using biochemical tests and growth rate. Molecular fingerprinting of all M. tuberculosis strains was performed by IS 6110 RFLP, spoligotyping and MIRU-VNTR. Results M. tuberculosis strains were isolated from 53 Iraqi patients with pulmonary TB. Spoligotyping of M. tuberculosis isolates showed T family (30%) as the predominant genotype. By using the three molecular techniques, there were four spoligotyping clusters of strains (“3540 & 3516”, “3565 & 3563”, “3605 & 3618” and “865, 877 & 13811”). Complete concordance with RFLP was observed in one cluster of spoligotyping, but no concordance with MIRU-VNTR profile (234426153433 and 236424183433). Conclusions Molecular fingerprinting methods are vital for differentiating a reactivation of latent infection from a recent transmission; however, it should be coupled with clinical epidemiological investigation. The low clustering rate in this study suggests that either reactivation of latent infections may be the main driving force for the endemic situation of the disease in Duhok, or it may indicate that a big circle of TB transmission is missed in the community, which means effective control measures have not been achieved yet in Duhok.