Prevalence and Distribution of Multidrug-Resistant Mutations in Mycobacterium tuberculosis in Tanzania

Background: Molecular identification of mutations resulting in multidrug-resistant tuberculosis (MDR-TB) is an important approach for improving understanding of MDR-TB epidemiology and planning for appropriate interventions. We aimed to estimate the prevalence and distribution of mutations causing MDR-TB as well as determine the gene distribution among patients previously treated for TB. Methods: This was a cross-sectional, hospital-based study conducted from April 2017 to October 2018 at Kibong’oto Infectious Diseases Hospital (KIDH). KIDH is the national MDR-TB referral hospital. Participants were patients presumptively diagnosed with MDR-TB and referred to KIDH from district and regional hospitals across Tanzania. Sputum samples were collected and analysed using the Xpert MTB/RIF assay, direct sputum smear fluorescence microscopy, culture on Lowenstein-Jensen medium, and line probe assay using the GenoType MTBDRplus VER 2.0 system. Demographic information and mutation frequencies were reported as counts and percentages and analysed using descriptive statistics. Results: A total of 208 (69.3%) participants had rpoB gene mutations conferring resistance to only rifampicin; 92 (30.7%) had rpoB, katG, and inhA mutations conferring resistance to rifampicin and isoniazid; 78 (26%) had rpoB and katG mutations conferring resistance to rifampicin and isoniazid; and 14 (4.7%) had rpoB and inhA mutations conferring resistance to rifampicin and isoniazid. Conclusion: The mutation prevalences identified in this study indicate the most frequent mutations were the S531L mutation of the rpoB gene, the S315T1 mutation of the katG gene, and the S315T mutation in the promoter region of the inhA gene. To control the emergence and spread of MDR-TB, drug sensitivity testing must be carried for GeneXpert-confirmed TB patients prior to initiating second-line anti-TB regimens.