Genotyping and drug susceptibility testing of Mycobacterium tuberculosis isolates from Iran

Abstract

Aims and objectives: Tuberculosis (TB) continues to be an important public health problem in the world. Genotyping of Mycobacterium tuberculosis MTB isolates will contribute to understanding and controlling the spread of the strains. This study aimed to determine the epidemiology of tuberculosis in Iran and to analyze the relationship between bacterial genotype and drug resistance. Methods: Spoligotyping and proportion method of drug susceptibility testing (DST) were used to determine genetic diversity and drug susceptibility of 291 MTB isolates respectively. Results: Spoligotyping produced 75 distinct patterns. 251 isolates (86.2%) were grouped in 35 clusters, while the remaining isolates showed a unique pattern. Ural (34.3%), Central Asian strain (CAS) (24%), T (18.2%), MANU2 (7.5%) and Latin American-Mediterranean (LAM) (6.1%) were found to be five common lineages of the studied population. The five largest clusters were Ural/SIT127 (15.8%), CAS1/SIT26 (9.2%), T1/SIT53 (6.1%), T1/SIT284 (5.4%) and CAS1/SIT25 (4.4%). According to spoligotyping data, 74.2% of infections were attributed to recent transmission. About 5% of isolates had multi-drug resistance (MDR) which was significantly associated with the Beijing genotype. Despite the high prevalence, the Ural family was not characterized with MDR. Conclusions: The present study highlights dominance of Ural, CAS and T families in Iran. The high rate of clustering obtained by this method suggests that recent transmission probably contributes more to TB infections rather than reactivation in this area. Bio-geographical specificity of CAS and T families to border provinces of Iran including Sistan-Baluchestan and Kermanshah, respectively, suggested that these family strains might be transmitted from these regions to other provinces of the country.

Keywords

• Iran
• MDR-TB
• Mycobacterium tuberculosis
• Spoligotyping