Estimation of Recent Transmission of Mycobacterium Tuberculosis Strains among Iranian and Afghan Immigrants: A Cluster-Based Study.
BACKGROUND
Iran has extended borders with high-TB burden countries (Afghanistan and Pakistan) and immigrations of these populations influences TB distribution in the region and threatens the control strategies. The aim of this study was to evaluate the extent of recent TB transmission among Iranian and Afghan cases.


METHODS
Spoligotyping and 15-locus variable number tandem repeat (VNTR) typing were applied to genotype 102 MTB isolates (2009 to 2010). Phylogenetic relationships were analysed by two methods: a cluster-graph method and a minimum spanning tree (MST) method. Furthermore, evaluation of recent TB transmission was assessed with three indices including, RTIn, RTIn-1 and TMI.


RESULTS
Using molecular typing, 35 different spoligotypes were detected among the studied isolates. Seventy seven cases (75.4%) were distributed into 10 clusters and the remaining 25 (24.5%) isolates had a unique pattern. The cluster sizes also ranged from 2 to 21 isolates. The most frequent spoligotype in our populations belong to Haarlem (n=30, 29.4%) followed by CAS (n= 29, 28.4%) and Beijing (n=16, 15.6%) lineages. The used indices give the following values: RTIn = 0.75, RTIn-1 = 0.65 and TMI = 0.24.


CONCLUSIONS
The low rate of TB transmission in our findings (24%) showed that the mode of TB transmission in Iran is mostly associated with reactivation of a previous TB infection and that recently a transmitted disease has a minor role. However, the increasing incidence of the intra-community transmission in recent years highlights the need for establishing new strategies for control of TB.
Post Graduate, Department of Microbiology, Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD),Shahid Beheshti University of Medical Sciences , Tehran, Iran .
Mohammad Reza Allahyar
MR
Torkaman
PhD Student, Department of Microbiology, Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD),Shahid Beheshti University of Medical Sciences , Tehran, Iran .
Mohammad Javad
MJ
Nasiri
Associated Professor, Department of Microbiology, Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD),Shahid Beheshti University of Medical Sciences , Tehran, Iran .
Parissa
P
Farnia
Associated Professor, Department of Microbiology, Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD),Shahid Beheshti University of Medical Sciences , Tehran, Iran .
Mohammad Hasan
MH
Shahhosseiny
Post Graduate, Department of Microbiology, Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD),Shahid Beheshti University of Medical Sciences , Tehran, Iran .
Mohadeseh
M
Mozafari
Professor, Department of Microbiology, Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD),Shahid Beheshti University of Medical Sciences , Tehran, Iran .
Ali Akbar
AA
Velayati
Cluster-graph method; Genotyping; Iran; Minimum spanning tree; Mycobacterium tuberculosis; Transmission