Molecular Epidemiology of Mycobacterium Tuberculosis Strains in the North‑West and West of Iran

Abstract

Background: Identifying Mycobacterium tuberculosis (MTB) transmission type is a key step in the control of this disease.
Aim: This study aimed to determine the path and transmission type of MTB and the insertion sequence IS6110 band number and verify their relationship to demographic and clinical risk factors.
Subjects and Methods: In this cross‑sectional study, 64 MTB patients from three border provinces of Iran were selected after full clinical history and physical evaluation design. The drug susceptibility testing was carried out using the standard proportion technique on sputum samples. Isolates tested with restriction fragment length polymorphism technique used IS6110.
Results: Recent transmission of disease was 33/50 (66%) based on clustering rate. The IS6110 band number had a significant relationship with drug resistance detected in proportion method tested by univariate linear regression (P < 0.01). Furthermore, the IS6110 band number had association with Bacillus Calmette–Guérin vaccination history (P = 0.02), sex (P < 0.01), and purified protein derivative (PPD) reaction size (P < 0.01) tested by multiple analysis. The risk of recent transmission inferred from the clustering rate was significantly higher in patients from Western provinces compared to those from the North‑West province (P = 0.048). However, age (P = 0.39), gender (P = 0.16), vaccination history (P = 0.57), drug susceptibility, and PPD (P = 0.6) were independent of clustering. The largest cluster of up to six subjects was found in the Western provinces.
Conclusion: Recent MTB transmission was much more common in the West compared to the North‑West of Iran. Large MTB clusters with strong epidemiological links may be reflective of a disease outbreak. Correlation noted between the IS6110 band number and vaccination history; PPD size and female gender necessitates further studies.

Keywords: Molecular epidemiology, Mycobacterium tuberculosis, Polymorphism, Restriction fragment length