Abstract
BackgroundThere is a perception that genomic differences in the species/lineages of the nine species making the Mycobacterium tuberculosis complex (MTBC) may affect the efficacy of distinct control tools in certain geographical areas. We therefore analyzed the prevalence and spatial distribution of MTBC species and lineages among isolates from pulmonary TB cases over an 8-year period, 2007–2014.MethodologyMycobacterial species isolated by culture from consecutively recruited pulmonary tuberculosis patients presenting at selected district/sub-district health facilities were confirmed as MTBC by IS6110 and rpoß PCR and further assigned lineages and sub lineages by spoligotyping and large sequence polymorphism PCR (RDs 4, 9, 12, 702, 711) assays. Patient characteristics, residency, and risks were obtained with a structured questionnaire. We used SaTScan and ArcMap analyses to identify significantly clustered MTBC lineages within selected districts and spatial display, respectively.ResultsAmong 2,551 isolates, 2,019 (79.1%), 516 (20.2%) and 16 (0.6%) were identified as M. tuberculosis sensu stricto (MTBss), M. africanum (Maf), 15 M. bovis and 1 M. caprae, respectively. The proportions of MTBss and Maf were fairly constant within the study period. Maf spoligotypes were dominated by Spoligotype International Type (SIT) 331 (25.42%), SIT 326 (15.25%) and SIT 181 (14.12%). We found M. bovis to be significantly higher in Northern Ghana (1.9% of 212) than Southern Ghana (0.5% of 2339) (p = 0.020). Using the purely spatial and space-time analysis, seven significant MTBC lineage clusters (p< 0.05) were identified. Notable among the clusters were Ghana and Cameroon sub-lineages found to be associated with north and south, respectively.ConclusionThis study demonstrated that overall, 79.1% of TB in Ghana is caused by MTBss and 20% by M. africanum. Unlike some West African Countries, we did not observe a decline of Maf prevalence in Ghana.
Highlights
One of the major threats to tuberculosis (TB) control is the emergence of strains that are resistant to most of the anti-TB drugs, which could make a treatable disease untreatable [1]
The proportions of M. tuberculosis sensu stricto (MTBss) and M. Africanum (Maf) were fairly constant within the study period
Maf spoligotypes were dominated by Spoligotype International Type (SIT) 331 (25.42%), SIT 326 (15.25%) and SIT 181 (14.12%)
Summary
One of the major threats to tuberculosis (TB) control is the emergence of strains that are resistant to most of the anti-TB drugs, which could make a treatable disease untreatable [1]. Mycobacterium tuberculosis sensu stricto and M. africanum are the main causative agents of TB in humans; referred to as human adapted MTBC and the remaining seven species as animal adapted [3]. The human adapted MTBC comprises seven main phylogenetic lineages, which have been confirmed by single nucleotide polymorphisms (SNPs) and whole genome sequencing [3, 10,11,12]. These lineages were further found to exhibit a phylogeographical structure, which means that specific lineages are closely associated with specific geographic regions, and preferentially infect persons originating from these regions. We analyzed the prevalence and spatial distribution of MTBC species and lineages among isolates from pulmonary TB cases over an 8-year period, 2007–2014
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