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

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.

Macrophage susceptibility to infection by Ghanaian Mycobacterium tuberculosis complex lineages 4 and 5 varies with self-reported ethnicity

“…Phenotypic studies on in vitro growth assessment revealed slower growth of L5 strains compared to L4 isolates (Gehre et al, 2013;Ates et al, 2018;Osei-Wusu et al, 2021). The slow growth of L5 has been attributed to its attenuated virulence.…”

An updated evolutionary history and taxonomy ofMycobacterium tuberculosislineage 5, also calledM. africanum

“…L5-caused tuberculosis represents an important part of all tuberculosis in some important regions from Africa such as Nigeria, Benin, Cameroun, Ghana i.e . in countries bordering the gulf of Guinea (Coscolla et al, 2021; Gehre et al, 2013; Gygli et al, 2019; Osei-Wusu et al, 2021; Sanoussi et al, 2021; Silva et al, 2022). But in Togo for example, the data of L5-L6 prevalence remains completely unknown.…”

Tuberculosis caused by Mycobacterium africanum: Knowns and unknowns

“…africanum strains present a slower growth rate in axenic medium, which is particularly visible in the case of L6 [ 48 – 51 ]. A lower growth rate for both L5 and L6 strains as compared to L4 ones was also documented in 7H11 solid medium and in 7H9 liquid medium [ 47 ]. Also remarkable is the evidence that M .…”

“…A recent study confirmed the preference of M . africanum L5 and L6 strains for pyruvate over glycerol as a carbon source, even though L5 also grows in media with glycerol [ 47 ]. Furthermore, several studies show that, as compared to M .…”

“…tuberculosis L4 and M . africanum L6 strains present a stronger average urease activity, which is directly linked to the bacteria nitrogen metabolism, than L5 [ 47 ]. Therefore, globally, L5 and L6 strains present several characteristics that are distinctive of M .…”