Molecular Epidemiology of Drug Resistant Strains of Tuberculosis in Bangladesh

Abstract

Tuberculosis (TB) is one of the top 10 causes of death worldwide. According to the Global TB Report globally in 2015, there were an estimated 10.4 million incident cases of Tuberculosis (TB) of which 5.9 million (56%) were among men, 3.5 million (34%) among women and 1.0 million (10%) among children. In 2015, the gap between notifications of new cases and the estimated number of incident was 4.3 million (missing cases) reflecting a mixture of undetected cases and under-reporting of detected TB cases. Bangladesh is one of the world’s most densely populated countries, with 161 million people. In recent years, Bangladesh has made significant progress in child and maternal mortality reduction, life expectancy and poverty reduction. However, Bangladesh still faces serious health challenges and Tuberculosis is one of them. According to WHO Global TB report 2016, with annual occurrence of 362,000 new Tuberculosis cases Bangladesh is one of the world’s 30 high TB burden countries. About 73,000 people die annually due to Tuberculosis. The National TB Programme (NTP) of Bangladesh and its partners have maintained good “basic TB control services”, with reasonable case detection and excellent treatment outcomes. The Government of Bangladesh, the Global Fund, USAID and other partners have kept their financial commitment to TB control during recent years, enabling NTP to consolidate its activities and address challenges of TB/HIV, multidrug resistant (MDR) TB, intensified case-finding in high-risk groups and vulnerable populations, and use of new technologies. There has been consistent increase in case notification especially among new and relapse cases since 2013. Bangladesh is the first country in the Region to introduce a shorter treatment regimen for MDR-TB and is achieving high cure rate for MDR-TB patients (75%). This study was aimed to early diagnosis of susceptible TB and prevents drug-resistant TB and improves the overall understanding of genotpypic diversity of MTBC strains circulating in Bangladesh. The research was conducted in NTRL, NIDH, Mohakhali and Department of Microbiology, University of Dhaka, Dhaka, Bangladesh and total 371 sputum samples from tuberculosis reference laboratory were collected. We have conducted two state-of-the-art molecular techniques: i) Spacer oligotyping/spoligotyping and ii) MIRU-VNTR (mycobacterial interspersed repetitive units-variable number of tandem repeats). In this study we found that most prevalent tuberculosis clade in Bangladesh is the Beijing clade and constitutes about 33.15% which is identified through Spoligotyping. Two different spoligotypes of Beijing clade including SIT 941 (9.19%) and SIT 1 (23.78%) was found. Evidence of presence of SIT 941 indicates its recent rapid spread in Bangladesh and it might be due to the extensive coverage of BCG vaccines. Moreover, two different types of MIRU-VNTR patterns were observed for the same spoligotype. This is possible as discriminatory power of MIRU-VNTR technique is more than spoligotyping technique. Although, MIRU-VNTR results could not be imparted with spoligotyping data, the spoligotyping technique alone was sufficient to identify predominant clades like Beijing, T1 and EAI in Bangladeshi population.