Back-to-Africa introductions of Mycobacterium tuberculosis as the main cause of tuberculosis in Dar es Salaam, Tanzania
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Date
2023
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
PLOS PATHOGENS
Abstract
In settings with high tuberculosis (TB) endemicity, distinct genotypes of the Mycobacterium
tuberculosis complex (MTBC) often differ in prevalence. However, the factors leading to
these differences remain poorly understood. Here we studied the MTBC population in Dar
es Salaam, Tanzania over a six-year period, using 1,082 unique patient-derived MTBC
whole-genome sequences (WGS) and associated clinical data. We show that the TB epidemic in Dar es Salaam is dominated by multiple MTBC genotypes introduced to Tanzania
from different parts of the world during the last 300 years. The most common MTBC genotypes deriving from these introductions exhibited differences in transmission rates and in the
duration of the infectious period, but little differences in overall fitness, as measured by the
effective reproductive number. Moreover, measures of disease severity and bacterial load
indicated no differences in virulence between these genotypes during active TB. Instead,
the combination of an early introduction and a high transmission rate accounted for the high
prevalence of L3.1.1, the most dominant MTBC genotype in this setting. Yet, a longer coexistence with the host population did not always result in a higher transmission rate, suggesting that distinct life-history traits have evolved in the different MTBC genotypes. Taken
together, our results point to bacterial factors as important determinants of the TB epidemic
in Dar es Salaam.
Description
Research Article
Keywords
tuberculosis, Tanzania
Citation
Citation: Zwyer M, Rutaihwa LK, Windels E, Hella J, Menardo F, Sasamalo M, et al. (2023) Back-to Africa introductions of Mycobacterium tuberculosis as the main cause of tuberculosis in Dar es Salaam, Tanzania. PLoS Pathog 19(4): e1010893. https://doi.org/10.1371/journal.ppat.1010893