Molecular characterization and drug susceptibility profile of Mycobacterium tuberculosis isolates from Northeast Bangladesh

Tuberculosis (TB) remains a major public health problem worldwide including in Bangladesh. Molecular epidemiological tools provide genotyping profiles of Mycobacterium tuberculosis (M. tuberculosis) strains that can give insight into the transmission of TB in a specific region. The objective of the study was to identify the genetic diversity and drug susceptibility profile of M. tuberculosis strains circulating in the northeast Bangladesh. A total of 244 smear-positive sputum specimens were collected from two referral hospitals in Mymensingh and Netrakona districts. The isolated strains were genotyped by deletion analysis, spoligotyping, and MIRU-VNTR typing. We also analyzed the distributions of drug susceptibility pattern and demographic data among different genotypes. All isolates were identified as M. tuberculosis and among them 167 strains (68.44%) were ‘ancestral’ and the remaining 77 (31.56%) were ‘modern’ type. Spoligotyping analysis yielded 119 distinct patterns, among them, 86 isolates had unique patterns and the remaining 158 were grouped into 33 distinct clusters containing 2 to 18 isolates. The predominant spoligotypes belong to the EAI lineage strains, comprising 66 (27.04%) isolates followed by Beijing (7.38%), T1 (6.15%), CAS1-Delhi (5.33), LAM9 (3.28%), MANU-2 and X2. MIRU-VNTR analysis revealed 167 isolates (68%) had unique patterns, whereas 77 (32%) were grouped into 26 clusters and the rate of recent transmission was 20.9%, suggesting that the majority of TB cases in this region are caused by the reactivation of previous TB infections rather than recent transmission. About 136 (55.7%) isolates were sensitive to four anti-TB drugs, 69 (28.3%) were resistant to one or more (except rifampicin and isoniazid combination) drugs and 39 (15.9%) were MDR. In conclusion, our study provides a first insight into molecular characterization and drug resistance profile of M. tuberculosis strains in northeast Bangladesh which will ultimately contribute to the national TB control program.