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

Abstract

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.