Molecular Epidemiology Analysis of TB in Five Regional States of Iran

BACKGROUND The increasing prevalence of TB drug resistant strains in absence of recent transmission evidence, highlights the need for an improved control program, coupled with a need to improve detection rate and early diagnosis. IS6110-RFLP is a means of genotyping TB clinical samples. In this study IS6110- RFLP was used for specification and quick tracking of TB infection source, transmission and reactivation of infection, in Iran. MATERIALS AND METHODS This study was carried out on 258 TB patients from Tehran, Mashhad, Isfahan, Shiraz and Ahwaz. DNA from positive cultures was extracted and digested by PVUII restriction enzyme. The digested sequences were separated based on the size on agar gel and then southern Blot was transferred on the membrane. IS6110 probe was marked by HRD and hybridized to the target parts along genome. RESULTS Sixty-one strains (24%) showed similar patterns (Recent transmission) and 197 strains (76%) showed different IS6110 patterns (Reactivation). Average number of IS6110 copies was between 10-11 bands. Frequency of IS6110 similar pattern was 11.46 in Afghan immigrants and 10.68 in Iranians. CONCLUSION High diversity of IS6110, indicates that 76% of the patients have been infected through reactivation by different sources, while 24% have been infected due to recent transmission. Observing different antibiogram patterns in patients infected with the same strain indicated vast transmission of a single strain in the society. A susceptible strain can be changed into mono drug resistant and MDR strain in the transition period.