Effects of Recent Transmission of Infection and Reactivation of Latent Infection with Mycobacterium Tuberculosis in Patients with Tuberculosis

Mycobacterium tuberculosis is a successful worldwide human pathogen responsible for killing about three million people every year. It has been estimated that approximately one-third of the world population have latent infections of this pathogen. This study was performed to evaluate the role of recent transmission of infection and reactivation of latent infection with Mycobacterium tuberculosis in Markazi Province (Iran). Overall, 57 sputum specimens from smear-positive patients were collected from health centers in Markazi Province. The samples were then cultured by standard methods. Afterward, genomic DNA was extracted by chloroform-isoamyl alcohol. Genetic studies were conducted by Pvull restriction fragment length polymorphism (RFLP) and DNA hybridization with IS6110 and direct repeat (DR) probes. We observed a wide range of genetic diversity from Mycobacterium tuberculosis strains. Of 48 genotypes identified by IS6110-RFLP method, 41 were unique. On the other hand, 37 of 45 genotypes identified by DR-RFLP were unique. The variety of genetic patterns revealed that reactivation of latent infection with Mycobacterium tuberculosis has a more important role than recent transmission in the studied population. Our practical findings showed higher discriminatory power of IS6110-RFLP compared to DR-RFLP.