Genotypic and phenotypic diversity of Mycobacterium tuberculosis complex genotypes prevalent in West Africa.

Stephen Osei-Wusu,Diana Asandem,Dorothy Yeboah-Manu,Adwoa Asante-Poku,Prince Asare,Ishaque Mintah Siam,Isaac Darko Otchere,Kwadwo Asamoah Kusi,Sebastien Gagneux,Theophilus Afum,Abdul Basit Musah,Portia Morgan

doi:10.1371/journal.pone.0255433

Abstract

Findings from previous comparative genomics studies of the Mycobacterium tuberculosis complex (MTBC) suggest genomic variation among the genotypes may have phenotypic implications. We investigated the diversity in the phenotypic profiles of the main prevalent MTBC genotypes in West Africa. Thirty-six whole genome sequenced drug susceptible MTBC isolates belonging to lineages 4, 5 and 6 were included in this study. The isolates were phenotypically characterized for urease activity, tween hydrolysis, Thiophen-2-Carboxylic Acid Hydrazide (TCH) susceptibility, nitric oxide production, and growth rate in both liquid (7H9) and solid media (7H11 and Löwenstein–Jensen (L-J)). Lineage 4 isolates showed the highest growth rate in both liquid (p = 0.0003) and on solid (L-J) media supplemented with glycerol (p<0.001) or pyruvate (p = 0.005). L6 isolates optimally utilized pyruvate compared to glycerol (p<0.001), whereas L5 isolates grew similarly on both media (p = 0.05). Lineage 4 isolates showed the lowest average time to positivity (TTP) (p = 0.01; Average TTP: L4 = 15days, L5 = 16.7days, L6 = 29.7days) and the highest logCFU/mL (p = 0.04; average logCFU/mL L4 = 5.9, L5 = 5.0, L6 = 4.4) on 7H11 supplemented with glycerol, but there was no significant difference in growth on 7H11 supplemented with pyruvate (p = 0.23). The highest release of nitrite was recorded for L5 isolates, followed by L4 and L6 isolates. However, the reverse was observed in the urease activity for the lineages. All isolates tested were resistant to TCH except for one L6 isolate. Comparative genomic analyses revealed several mutations that might explain the diverse phenotypic profiles of these isolates. Our findings showed significant phenotypic diversity among the MTBC lineages used for this study.

Highlights

Tuberculosis (TB) remains a global health burden and it is the leading cause of human death from a single infectious agent [1]
Our findings showed significant phenotypic diversity among the Mycobacterium tuberculosis complex (MTBC) lineages used for this study
Ethical clearance was obtained from the Institutional Review Board (IRB) of Noguchi Memorial Institute for Medical Research (NMIMR), University of Ghana (Federal wide assurance number: FWA00001824) and the Ethics Review Committee of the Korle-Bu Teaching Hospital

Summary

Introduction

Tuberculosis (TB) remains a global health burden and it is the leading cause of human death from a single infectious agent [1]. A number of studies have demonstrated the effects of strain diversity among bacterial pathogens [9,10,11,12,13]. These studies highlight the fact that certain strains may cause more invasive diseases than others due to differences in the expression of virulence factors either encoded chromosomally or carried on transmissible elements [14,15]. Examples of horizontal gene transfer which leads to acquisition of classical pathogenicity islands have not been reported in MTBC, the MTBC lineages and strains differ phenotypically [13,16,17]

Methods

Results

Discussion

Conclusion