Biology subjects

Rutaihwa, L. K.

Publications and source records attributed to Rutaihwa, L. K..

6 recordsLinked to original sources

bioRxiv2024

Human genetic ancestry, Mycobacterium tuberculosis diversity and tuberculosis disease severity in Dar es Salaam, Tanzania

Infectious diseases have affected humanity for millennia and are among the strongest selective forces. Tuberculosis (TB) is an ancient disease, caused by the human-adapted members of the Mycobacterium tuberculosis complex (MTBC). The outcome of TB infection and disease is highly variable, and co-evolution between human populations and MTBC strains may account for some of this variability. Particular human genetic ancestries have been associated with higher susceptibility to TB, but socio-demographic aspects of the disease can confound such associations. Here, we studied 1,000 TB patients from Dar es Salaam, Tanzania, together with their respective MTBC isolates, by combining human and bacterial genomics with clinical data. We found that the genetic background of the TB patient population was strongly influenced by migrationsof Bantu-speaking populations from West Africa, which is in contrast to the corresponding MTBC genotypes that were mainly introduced from outside Africa. These findings suggest a recent evolutionary history of co-existence between the human and MTBC populations in Dar es Salaam. We detected no evidence of an effect of human genetic ancestry, or MTBC phylogenetic diversity alone, nor their interaction, on TB disease severity. There was also no evidence of an association between human variation genome-wide and TB disease severity.Treatment-seeking, social and environmental factors are likely to be the main determinants of disease severity at the point of care in this patient population. Author SummaryTuberculosis (TB) is an ancient infectious disease that continues to challenge global health efforts. Here, we explored the interplay between human and bacterial genetics on TB in Dar es Salaam, Tanzania. We found that neither the genetic ancestry of the patient, nor the bacterial genotype alone, nor their interaction, influenced the severity of TB. Our finding indicate that in this patient population, social and environmental factors may be the main determinants of TB disease severity.

evolutionary biology↗

bioRxiv2023

Comparison of different genotyping techniques to distinguish recrudescence from new infection in studies assessing the efficacy of antimalarial drugs against Plasmodium falciparum

Distinguishing recrudescence from new infections is crucial for the assessment of antimalarial drug efficacy against Plasmodium falciparum (P. falciparum). Different genotyping methods are used and may impede the comparison of drug efficacy estimates in space and time, particularly in patients from high transmission settings with polyclonal infections. We compared five different genotyping methods currently used to assess their sensitivity in detecting minority clones in polyclonal infections, their robustness, and the genetic diversity of the markers used. Our study utilized four well-characterized P. falciparum laboratory strains mixed in varying ratios, and 20 paired patient samples collected from a clinical trial. We found that high-resolution capillary electrophoresis (H-CE) using length-polymorphic markers, as well as targeted amplicon deep sequencing (TADS) using single nucleotide polymorphism (SNP)-rich markers, revealed the highest sensitivity in detecting minority clones, while also exhibiting robustness, and high genetic diversity in the used markers. Moreover, markers used by TADS gave more consistent results. We observed that microsatellites had a lower genetic diversity compared to markers such as msp1, msp2, glurp and SNP-rich markers, with some genotypes having allelic frequencies of > 30 %. The replacement of glurp by microsatellites did not result in a change in the genotyping outcome, probably due to the lower genetic diversity of microsatellites used in comparison to glurp. More studies with large sample sizes are necessary to identify the most suitable microsatellites that could replace glurp as per the latest recommendations from the World Health Organization (WHO) on genotyping to distinguish recrudescence from new infections in high transmission settings. Our study indicates that TADS should be considered the gold standard for genotyping to differentiate recrudescence from new infection and should be used to validate other techniques.

molecular biology↗

bioRxiv2020

Local adaptation in populations of Mycobacterium tuberculosis endemic to the Indian Ocean Rim

Lineage 1 (L1) and 3 (L3) are two lineages of the Mycobacterium tuberculosis complex (MTBC), causing tuberculosis (TB) in humans. L1 and L3 are endemic to the Rim of the Indian Ocean, the region that accounts for most of the worlds new TB cases. Despite their relevance for this region, L1 and L3 remain understudied. Here we analyzed 2,938 L1 and 2,030 L3 whole genome sequences originating from 69 countries. We show that South Asia played a central role in the dispersion of these two lineages to neighboring regions. Moreover, we found that L1 exhibits signatures of local adaptation at the esxH locus, a gene coding for a secreted effector that targets the human endosomal sorting complex, and is included in several vaccine candidates. Our study highlights the importance of genetic diversity in the MTBC, and sheds new light on two of the most important MTBC lineages affecting humans.

genomics↗

bioRxiv2020

HIV coinfection is associated with low fitness rpoB variants in rifampicin-resistant Mycobacterium tuberculosis

We analysed 312 drug-resistant genomes of Mycobacterium tuberculosis (Mtb) collected from HIV coinfected and HIV negative TB patients from nine countries with a high tuberculosis burden. We found that rifampicin-resistant Mtb strains isolated from HIV coinfected patients carried disproportionally more resistance-conferring mutations in rpoB that are associated with a low fitness in the absence of the drug, suggesting these low fitness rpoB variants can thrive in the context of reduced host immunity.

evolutionary biology↗

bioRxiv2018

Insights into the genetic diversity of Mycobacterium tuberculosis in Tanzania

BackgroundHuman tuberculosis (TB) is caused by seven phylogenetic lineages of the Mycobacterium tuberculosis complex (MTBC), Lineage 1-7. Recent advances in rapid genotyping of MTBC based on single nucleotide polymorphisms (SNP), allow for rapid and phylogenetically robust strain classification, paving the way for defining genotype-phenotype relationships in clinical settings. Such studies have revealed that, in addition to host and environmental factors, different strains of the MTBC influence the outcome of TB infection and disease. In Tanzania, such molecular epidemiological studies of TB however are scarce in spite of a high TB burden.\n\nMethods and FindingsHere we used a SNP-typing method to genotype a nationwide collection of 2,039 MTBC clinical isolates obtained from new and retreatment TB cases diagnosed in 2012 and 2013. Four lineages, namely Lineage 1-4 were identified. The distribution and frequency of these lineages varied across the regions but overall, Lineage 4 was the most frequent (n=866, 42.5%), followed by Lineage 3 (n=681, 33.4%) and 1 (n=336, 16.5%), with Lineage 2 being the least frequent (n=92, 4.5%). A total of 64 (3.1%) isolates could not be assigned to any lineage. We found Lineage 2 to be associated with female sex (adjusted odds ratio [aOR] 2.25; 95% confidence interval [95% CI] 1.38 - 3.70, p<0.001) and retreatment (aOR 1.78; 95% CI 1.00 - 3.02, p=0.040). We found no associations between MTBC lineage and patient age or HIV status. Our sublineage typing based on spacer oligotyping revealed the presence of mainly EAI, CAS and LAM families. Finally, we detected low levels of multidrug resistant isolates among a subset of retreatment cases\n\nConclusionsThis study provides novel insights into the influence of pathogen-related factors on the TB epidemic in Tanzania.

epidemiology↗

bioRxiv2018

Multiple Introductions of the Mycobacterium tuberculosis Lineage 2 Beijing into Africa over centuries

The Lineage 2-Beijing (L2-Beijing) sub-lineage of Mycobacterium tuberculosis has received much attention due to its high virulence, fast disease progression, and association with antibiotic resistance. Despite several reports of the recent emergence of L2-Beijing in Africa, no study has investigated the evolutionary history of this sub-lineage on the continent. In this study, we used whole genome sequences of 817 L2 clinical strains from 14 geographical regions globally distributed to investigate the origins and onward spread of this lineage in Africa. Our results reveal multiple introductions of L2-Beijing into Africa linked to independent bacterial populations from East-and Southeast Asia. Bayesian analyses further indicate that these introductions occurred during the past 300 years, with most of these events pre-dating the antibiotic era. Hence, the success of L2-Beijing in Africa is most likely due to its hypervirulence and high transmissibility rather than drug resistance.

evolutionary biology↗