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Understanding the genetic structure and transmission dynamics of Plasmodium falciparum parasites in malaria-endemic regions is crucial before the implementation of interventions. Located in a high-transmission region of western Kenya where P. falciparum is the predominant species, the Lake Victoria islands are ideal for feasibility of malaria elimination studies. We analyzed genetic variation in eight microsatellite loci to examine parasite population structure and gene flow patterns across five sites. High levels of genetic diversity were measured throughout the region (mean heterozygosity index = 0.84). The overall fixation index value between the sites was 0.044, indicating that approximately 5% of the overall allelic variation is due to differences between the populations. Based on these results, we concluded that parasite population structure in the studied islands is shaped by human migration patterns that maintain extensive parasite gene flow between the sites. Consequently, any malaria elimination and interventions strategies in the study area will have to be carried out broadly on all four islands and adjoining mainland region.

Antimicrobial drug resistance is a rising concern in the treatment of infectious diseases and necessitates the need for discovery of novel, potent antimicrobial compounds to combat antibiotic resistance. Since natural environment remains a potential source of novel antimicrobial products, this preliminary study was performed to test the potential of soils from Kericho County for antibiotic-producing Actinomycetes. Soil samples (214) were randomly collected from virgin soils of Kipkelion East, Kipkelion West, Belgut, Ainamoi, Sigowet and Bureti sub-counties in Kericho County from a depth of between 11 cm -16 cm from the surface of the soil profile. A total of 107 Actinomycetes were isolated and screening was done using modified agar disc diffusion method of which only 39 (36.4%) showed antimicrobial activity against five of the six test isolates that included reference strains Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922) and Candida albicans (ATCC 90028) and three clinical strains Trichophyton mentagrophyte, Microsporum gypseum and Methicillin Resistant Staphylococcus aureus. Two of the isolates showed activity against MRSA and four isolates showed a higher potency than the standard drug Chloramphenicol (30 μg) against S. aureus. Most of the isolates (41.0%) also showed good antimicrobial activity against T. mentagrophyte, though they lower than the control drug Itraconazole (2 μg/ml), they were statistically significant. DNA from the isolates was extracted and the 16S rRNA gene was amplified using primers specific for Actinomycetes. The amplified gene was sequenced and phylogeny analysis was done. The 16S rRNA gene was able to be amplified in only 15 of these isolates. Sequencing showed that 93.3% were of the genus Streptomyces while 6.7% were of the genus Rhodococcus. From the results, the soils from this region harbour Actinomycetes that may have good potential of producing novel antibiotics against gram positive bacteria and dermatophytes.

β-amylase is a thermostable enzyme that hydrolyses starch during cooking of sweetpotato ( Ipomoea batatas ) storage roots, thereby influencing eating quality. Its activity is known to vary amongst genotypes but the genetic diversity of the beta-amylase gene ( Amyβ ) is not well studied. Amyβ has a highly conserved region between exon V and VI, forming part of the enzyme's active site. To determine the gene diversity, a 2.3 kb fragment, including the conserved region of the Amyβ gene was sequenced from 25 sweetpotato genotypes. The effect of sequence variation on gene expression, enzyme activity, and firmness in cooked roots was determined. Six genotypes carrying several SNPs within exon V, linked with an AT or ATGATA insertion in intron V were unique and clustered together. The genotypes also shared an A336E substitution in the amino acid sequence, eight residues upstream of a substrate-binding Thr344. The genotypes carrying this allele exhibited low gene expression and low enzyme activity. Enzyme activity was negatively correlated with firmness (R = −0.42) in cooked roots. This is the first report of such an allele, associated with low enzyme activity. These results suggest that genetic variation within the AmyB locus can be utilized to develop markers for firmness in sweetpotato breeding.

Frankliniella schultzeiTrybom is a polyphagous pest and vector of tospoviruses worldwide. It occurs in dark and pale colour forms that are morphologically similar but differ in vector competency and geographic spread. In Kenya and other tropical regions, mixed populations of both colour forms are observed in similar habitats, so are considered as one species. To ascertain the taxonomic status of the two colour forms, they were characterized using morphological, molecular, biological and ecological approaches. Morphological characterization revealed differences between the colour forms on eight features and they separated into distinct clusters through principal component analysis. Restriction fragment length polymorphism of the internal transcribed spacer region (ITS-RFLP) analysis revealed differences between the two colour forms and was confirmed by differences in ITS2 sequences. Virgin pale females had female offspring (thelytoky), while virgin dark females had male offspring (arrhenotoky). Interbreeding of dark males with pale females resulted in pale females, indicating absence of interbreeding between the two colour forms. Laboratory colonies of pale forms lacked males and further analysis ofF. schultzeimales fromIpomoea setosaflowers in the field indicated the presence of dark males and the absence of pale males. Field surveys in Kenya indicated differences in distribution and host plant preferences among the colour forms. Lack of interbreeding, distinct host preferences and distribution, and morphological and molecular differences indicate that the two colour forms ofF. schultzeicould be different species. The results highlight the need for combining morphological, biological, molecular and ecological characteristics for resolving taxonomic status of closely related insects.

Background: The human malaria parasite Plasmodium falciparum has evolved complex drug evasion mechanisms to all available antimalarials. To date, the combination of amodiaquine-artesunate is among the drug of choice for treatment of uncomplicated malaria. In this combination, a short acting, artesunate is partnered with long acting, amodiaquine for which resistance may emerge rapidly especially in high transmission settings. Here, we used a rodent malaria parasite Plasmodium berghei ANKA as a surrogate of P. falciparum to investigate the mechanisms of amodiaquine resistance. Methods: We used serial technique to select amodiaquine resistance by submitting the parasites to continuous amodiaquine pressure. We then employed the 4-Day Suppressive Test to monitor emergence of resistance and determine the cross-resistance profiles. Finally, we genotyped the resistant parasite by PCR amplification, sequencing and relative quantitation of mRNA transcript of targeted genes. Results: Submission of P. berghei ANKA to amodiaquine pressure yielded resistant parasite within thirty-six passages. The effective dosage that reduced 90% of parasitaemia (ED 90) of sensitive line and resistant line were 4.29mg/kg and 19.13mg/kg, respectively. After freezing at -80ºC for one month, the resistant parasite remained stable with an ED 90 of 18.22mg/kg. Amodiaquine resistant parasites are also resistant to chloroquine (6fold), artemether (10fold), primaquine (5fold), piperaquine (2fold) and lumefantrine (3fold). Sequence analysis of Plasmodium berghei chloroquine resistant transporter revealed His95Pro mutation. No variation was identified in Plasmodium berghei multidrug resistance gene-1 (Pbmdr1), Plasmodium berghei deubiquitinating enzyme-1 or Plasmodium berghei Kelch13 domain nucleotide sequences. Amodiaquine resistance is also accompanied by high mRNA transcripts of key transporters; Pbmdr1, V-type/H+ pumping pyrophosphatase-2 and sodium hydrogen ion exchanger-1 and Ca 2+/H + antiporter. Conclusions: Selection of amodiaquine resistance yielded stable “multidrug-resistant’’ parasites and thus may be used to study common resistance mechanisms associated with other antimalarial drugs. Genome wide studies may elucidate other functionally important genes controlling AQ resistance in P. berghei.