Abstract
Mycobacterium africanum is a member of the Mycobacterium tuberculosis complex (MTBC) and an important cause of human tuberculosis in West Africa that is rarely observed elsewhere. Here we genotyped 613 MTBC clinical isolates from Ghana, and searched for associations between the different phylogenetic lineages of MTBC and patient variables. We found that 17.1% (105/613) of the MTBC isolates belonged to M. africanum, with the remaining belonging to M. tuberculosis sensu stricto. No M. bovis was identified in this sample. M. africanum was significantly more common in tuberculosis patients belonging to the Ewe ethnic group (adjusted odds ratio: 3.02; 95% confidence interval: 1.67–5.47, p<0.001). Stratifying our analysis by the two phylogenetic lineages of M. africanum (i.e. MTBC Lineages 5 and 6) revealed that this association was mainly driven by Lineage 5 (also known as M. africanum West Africa 1). Our findings suggest interactions between the genetic diversity of MTBC and human diversity, and offer a possible explanation for the geographical restriction of M. africanum to parts of West Africa.
Highlights
Tuberculosis (TB) remains the leading cause of adult death by a single infectious disease world-wide [1]
Mycobacterium tuberculosis complex (MTBC) relevant to human disease has been classified into seven main phylogenetic lineages [3,4]: Lineages 1 to 4 together with Lineage 7 are collectively known as M. tuberculosis sensu stricto, whereas Lineage 5 and 6 are known as M. africanum West Africa I and II, respectively [5]
Human tuberculosis is caused by bacteria known as the Mycobacterium tuberculosis complex (MTBC)
Summary
Tuberculosis (TB) remains the leading cause of adult death by a single infectious disease world-wide [1]. In 2013, an estimated 9.0 million new cases and 1.5 million deaths due to TB occurred; with 30% of the global burden of TB occurring in Africa, an indication of the strong association with HIV/AIDS [1]. MTBC comprises M. tuberculosis sensu stricto and M. africanum which are the main agents of TB in humans, and several variants adapted to various domestic and wild mammal species, including M. bovis, M. caprae, M. microti and M. pinnipedii [2]. MTBC relevant to human disease has been classified into seven main phylogenetic lineages [3,4]: Lineages 1 to 4 together with Lineage 7 are collectively known as M. tuberculosis sensu stricto, whereas Lineage 5 and 6 are known as M. africanum West Africa I and II, respectively [5]
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