Phenotypic diversity of Mycobacterium tuberculosis complex genotypes prevalent in West Africa
Stephen Osei-Wusu, Isaac Darko Otchere, Portia Morgan, Basit Abdul Musa, Ishaque Mintah Siam, Diana Asandem, Prince Asare, Adwoa Asante-Poku & Dorothy Yeboah-Manu
Institution: Noguchi Memorial Institute for Medical Research, University of Ghana
Background: Comparative genomics studies of Mycobacterium tuberculosis complex (MTBC) indicate genomic variation among the genotypes with potential phenotypic implications. This study investigated the diversity in the phenotypic profiles of the main prevalent genotypes in West Africa.
Method: Thirty whole genome sequenced susceptible MTBC isolates belonging to lineages 4, 5 and 6 were included in this study. The isolates were grown on 7H11 media plates to the log phase. They were then phenotypically characterized for urease activity, tween hydrolysis, Thiophen-2-Carboxylic Acid Hydrazide (TCH) susceptibility, growth rate in 7H9 medium supplemented with pyruvate and ADC, either glycerol or pyruvate as carbon source. Comparative genomic analysis was carried out to explain the phenotypic differences observed among the different lineages.
Results: Lineage 4 showed the highest growth rate compared to L5(p=0.026) and L6(p= 0.0002) Three mutations (R16P, Y98H & V75I) in the ftsE gene which is associated with cell division and 2 mutations in the pstP (Phosphoserine/Threonine Phosphatase) were found in L5 and L6 isolates. A mutation (E71stop) in whiB3 (a transcriptional Regulatory Protein) was found in all L5 isolates. Utilization of glycerol as the sole carbon source was significantly higher in L4 compared to L6 on L-J media (p=0.042). Lineage 4 and 6 were positive for urease activity while L5 was negative. Two mutations (G98D & Y169C) in the Rv1395 (a transcriptional regulatory proteins) and the mutation (T125I) in the mrsA (probable phospho-sugar mutase) were observed in L5 isolates specifically L5.3 and L5.1 respectively. Also, all isolates tested were resistant to TCH expect one isolate (L6.3). A mutation (R463L) in the katG among all L5 and L6 strains could be responsible for the observed resistance to TCH.
Conclusion: We observed significant phenotypic diversity among the prevalent MTBC lineages in West Africa which may have implications on the variation in virulence