Abstract
BackgroundMycobacterium africanum comprises two phylogenetic lineages within the M. tuberculosis complex (MTBC) and is an important cause of human tuberculosis (TB) in West Africa. The reasons for this geographic restriction of M. africanum remain unclear. Here, we performed a prospective study to explore associations between the characteristics of TB patients and the MTBC lineages circulating in Ghana.MethodWe genotyped 1,211 MTBC isolates recovered from pulmonary TB patients recruited between 2012 and 2014 using single nucleotide polymorphism typing and spoligotyping. Associations between patient and pathogen variables were assessed using univariate and multivariate logistic regression.ResultsOf the 1,211 MTBC isolates analysed, 71.9 % (871) belonged to Lineage 4; 12.6 % (152) to Lineage 5 (also known as M. africanum West-Africa 1), 9.2 % (112) to Lineage 6 (also known as M. africanum West-Africa 2) and 0.6 % (7) to Mycobacterium bovis. Univariate analysis revealed that Lineage 6 strains were less likely to be isoniazid resistant compared to other strains (odds ratio = 0.25, 95 % confidence interval (CI): 0.05–0.77, P < 0.01). Multivariate analysis showed that Lineage 5 was significantly more common in patients from the Ewe ethnic group (adjusted odds ratio (adjOR): 2.79; 95 % CI: 1.47–5.29, P < 0.001) and Lineage 6 more likely to be found among HIV-co-infected TB patients (adjOR = 2.2; 95 % confidence interval (CI: 1.32–3.7, P < 0.001).ConclusionOur findings confirm the importance of M. africanum in Ghana and highlight the need to differentiate between Lineage 5 and Lineage 6, as these lineages differ in associated patient variables.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1725-6) contains supplementary material, which is available to authorized users.
Highlights
Mycobacterium africanum comprises two phylogenetic lineages within the M. tuberculosis complex (MTBC) and is an important cause of human tuberculosis (TB) in West Africa
Multivariate analysis showed that Lineage 5 was significantly more common in patients from the Ewe ethnic group (adjusted odds ratio: 2.79; 95 % CI: 1.47–5.29, P < 0.001) and Lineage 6 more likely to be found among human immunodeficiency virus infection (HIV)-co-infected TB patients (adjOR = 2.2; 95 % confidence interval (CI: 1.32–3.7, P < 0.001)
Our findings confirm the importance of M. africanum in Ghana and highlight the need to differentiate between Lineage 5 and Lineage 6, as these lineages differ in associated patient variables
Summary
Mycobacterium africanum comprises two phylogenetic lineages within the M. tuberculosis complex (MTBC) and is an important cause of human tuberculosis (TB) in West Africa. The reasons for this geographic restriction of M. africanum remain unclear. Human TB is mainly caused by Mycobacterium africanum (MAF) and Mycobacterium tuberculosis sensu stricto (MTB), both members of Mycobacterium tuberculosis complex (MTBC), which includes several sub-species adapted to a variety of wild and domestic animals [2, 3]. MAF first identified in 1968 in Senegal, was initially described biochemically as an intermediary between MTB and M. bovis [4]. Initial biochemical features subdivided MAF into two separate groups; the West-African sub-species and East-African referred
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