Browsing by Author "Kimani, Francis"

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    Persistent and Circulating Plasmodium falciparum dhfr and dhps Mutations in Busia County, Western Kenya
    (Pathogens, 2026-02) Ndung’u, Loise; Thiong’o, Kelvin; Karani, Lewis; Gitahi, Stephen; Kimani, Francis; Ngugi, Mathew Piero; Kiboi, Daniel
    Malaria in pregnancy remains a major driver of poor maternal and neonatal health outcomes in sub-Saharan Africa. For decades, intermittent preventive treatment in pregnancy (IPTp), with sulphadoxine-pyrimethamine (SP), has mitigated malaria-associated health risks, but concerns have been raised regarding accumulated Plasmodium falciparum dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) mutations on the efficacy of SP. Western Kenya, including Busia County, is a high malaria transmission setting where molecular surveillance of dhfr and dhps mutations remains limited. This study assessed the prevalence and haplotype structure of dhfr and dhps mutations in P. falciparum isolates from Busia County, Kenya. A total of 66 samples of P. falciparum isolates collected from patients attending Matayos Sub-County Hospital between November 2024 and January 2025 were analysed. PCR amplification and Sanger sequencing targeted dhfr codons C50R, N51I, C59R, S108N/T, I164L, and dhps codons I431V, S436A/F, A437G, K540E, A581G, and A613S/T to determine mutation frequencies, haplotypes, and combined dhps and dhfr haplotype profiles. High frequencies of dhfr and dhps mutations were observed across the parasite isolates. The most common dhfr substitutions included N51I (85.2%) and C59R (75.4%), while S108N (32.8%) and S108T (19.7%) were detected at lower frequencies. Dhfr haplotypes identified included N51I + C59R, N51I + C59R + S108N, and a N51I + C59R + S108T + I164L variant. The I164L mutation was detected at a frequency of 18.0% and was observed exclusively on a non-canonical S108T background (19.7%). Dhps haplotypes were dominated by A437G (92.3%), K540E (40%) alone, and the A437G + K540E double mutant. Combined dhfr and dhps haplotype analyses revealed circulation of classical dhfr triple-mutant (N51I + C59R + S108N) backgrounds with dhps A437G. Quintuple haplotypes (dhfr N51I + C59R + S108T + I164L with dhps A437G) and rare complex haplotypes incorporating both I164L and K540E or I164L and S436F were also detected. These findings indicate the persistence and circulation of both canonical and non-canonical dhfr and dhps haplotypes in P. falciparum isolates from Busia County. This study highlights the need for continuous molecular and phenotypic surveillance to clarify the functional and epidemiological significance of parasites carrying S108T and I164L mutations, and to inform IPT policy.
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    Synergistic antiplasmodial activity of artemisia annua fractions against in vitro cultures of plasmodium falciparum
    (2016) Kangethe, Lucy N.; Ahmed, Hassanali; Omar, Sabah; Gathirwa, Jeremiah; Kirira, Peter; Kaniaru, Stephen; Kamau, Timothy; Kimani, Francis; Nganga, Joseph K.; Irungu, Lucy
    Background: Artemisia annua has a very rich phytochemistry comprising several classes of compounds, mainly monoterpenes, sesquiterpenes, and flavonoids. It has been used in China for about 2000 years in the treatment of fever. Objective: The aim was to determine if there is any synergistic effect on the Artemisia annua phytochemicals. Materials and methods: Artemisia annua used in this study was obtained from a hybrid of the plant grown in the Tanzania highlands (2000-2200 m altitude) in Arusha by Natural Uwemba System for Health (N.U.S.Ag). The dried leaves were ground, and sequentially extracted with hexane, dichloromethane (DCM), methanol and water and the extracts were then combined. The extract was then fractionated using high performance liquid chromatography (HPLC). The effect of the combined crude extract was tested at different doses on in-vitro cultures (a CQ sensitive isolate D6 and CQ resistant isolate W2) of Plasmodium falciparum. The fractions and different blends of these were tested at different doses to determine their role, if any, on the activity of the full blend of the plant. Results: Of nine fractions thus tested against D6 and W2, four had activities of less than 3.9μg /ml, three fractions had activities of between 4.77-14.76 μg/ml and the remaining two had activities above 250g/μml. The seven more active fractions were re-evaluated in a subtractive bioassay procedure, in which one of each fraction was excluded at a time from the full 7-component blend. The activity of the combined seven active compounds was 10.40+0.50 μg/ml against W2. Of these, one showed IC50 of less than 3.9 μg/ml and all blends showed IC50 at below 27μg/ml. Conclusion: The results show that different components of A. annua contribute to the synergistic anti-Plasmodium activity. The results constitute a useful basis for identifying the components of the plant other than artemisinin that contribute to the activity of herb.