Short Report: Association Between Chloroquine and Amodiaquine Resistance and Allelic Variation in the Plasmodium Falciparum Multiple Drug Resistance 1 Gene and the Chloroquine Resistance Transporter Gene in Isolates from the Upper Nile in Southern Sudan.

Amodiaquine, a 4-aminoquinoline compound, is being considered as an alternative to chloroquine and pyrimethamine/sulfadoxine where resistance in Plasmodium falciparum to both drugs has been selected. Although amodiaquine is more potent than chloroquine, its effectiveness is reduced in areas where chloroquine resistance is high. We report an association of the P. falciparum chloroquine resistance transporter (pfcrt) gene and the P. falciparum multiple drug resistance 1 (pfmdr1) gene, two chloroquine resistance markers, with chloroquine and amodiaquine efficacy in vivo in southern Sudan. The data show that the allele of the pfcrt gene with a lysine to threonine change at codon 76 is strongly associated with both chloroquine and amodiaquine resistance. No such association was observed with the pfmdr1 gene

Effect of folate derivatives on the activity of antifolate drugs used against malaria and cancer

The folate derivatives folic acid (FA) and folinic acid (FNA) decrease the in vivo and in vitro activities of antifolate drugs in Plasmodium falciparum. However, the effects of 5-methyl-tetrahydrofolate (5-Me-THF) and tetrahydrofolate (THF), the two dominant circulating folate forms in humans, have not been explored yet. We have investigated the effects of FA, FNA, 5-Me-THF, and THF on the in vitro activity of the antimalarial antifolates pyrimethamine and chlorcycloguanil and the anticancer antifolates methotrexate (MTX), aminopterin, and trimetrexate (TMX), against P. falciparum. The results indicate that these anticancers are potent against P. falciparum, with IC50 < 50 nM. 5-Me-THF does not significantly decrease the activity of all tested drugs, and none of the tested folate derivatives significantly decrease the activity of these anticancers. Thus, malaria folate metabolism has features different from those in human, and the exploitation of this difference could lead to the discovery of new drugs to treat malaria. For instance, the combination of 5-Me-THF with a low dose of TMX could be used to treat malaria. In addition, the safety of a low dose of MTX in the treatment of arthritis indicates that this drug could be used alone to treat malaria

Fitness Trade-Offs in the Evolution of Dihydrofolate Reductase and Drug Resistance in Plasmodium falciparum

Background: Patterns of emerging drug resistance reflect the underlying adaptive landscapes for specific drugs. In Plasmodium falciparum, the parasite that causes the most serious form of malaria, antifolate drugs inhibit the function of essential enzymes in the folate pathway. However, a handful of mutations in the gene coding for one such enzyme, dihydrofolate reductase, confer drug resistance. Understanding how evolution proceeds from drug susceptibility to drug resistance is critical if new antifolate treatments are to have sustained usefulness. Methodology/Principal Findings: We use a transgenic yeast expression system to build on previous studies that described the adaptive landscape for the antifolate drug pyrimethamine, and we describe the most likely evolutionary trajectories for the evolution of drug resistance to the antifolate chlorcycloguanil. We find that the adaptive landscape for chlorcycloguanil is multi-peaked, not all highly resistant alleles are equally accessible by evolution, and there are both commonalities and differences in adaptive landscapes for chlorcycloguanil and pyrimethamine. Conclusions/Significance: Our findings suggest that cross-resistance between drugs targeting the same enzyme reflect the fitness landscapes associated with each particular drug and the position of the genotype on both landscapes. The possibl

Preparation of Silver/Chitosan Nanofluids Using Selected Plant Extracts: Characterization and Antimicrobial Studies against Gram-Positive and Gram-Negative Bacteria

Chitosan/silver nanofluids were prepared using Phoenix dactylifera (DPLE) or Rumex vesicarius (HEL) extracts as the reducing agent, characterized using Fourier-transform infrared spectroscopy (FTIR), ultraviolet–visible (UV-vis), X-ray di�raction (XRD), and transmission electron microscope (TEM). The antimicrobial e�ect of the nanofluids against Gram positive, Bacillus licheniformis, Staphylococcus haemolyticus, Bacillus cereus, and Micrococcus luteus, and Gram-negative Pseudomonas aeruginosa, Pseudomonas citronellolis, and Escherichia coli bacteria has been studied. The nanoparticles were polydispersed in the chitosan matrix and are highly stable. The zeta potential of the silver nanoparticles in DPLE- and HEL-mediated composites is +46 mV and +56 mV, respectively. The FTIR results reveal that the free carboxylate groups in the plant biomaterial took part in stabilization process. HEL is a stronger reducing agent than DPLE and nanoparticles generated with HEL are smaller (8.0–36 nm) than those produced with DPLE (10–43 nm). DPLE- and HEL-mediated composites e�ectively inhibit the growth of the studied bacteria but HEL-mediated composite exhibited higher e�ect. The higher antimicrobial activity of HEL-mediated composite is linked to the smaller nanoparticles. The foregoing results indicate that HEL extract can be used in the green production of potential antimicrobial chitosan/silver nanofluids for biomedical and packaging applications

Corrosion Inhibition of Rumex vesicarius Mediated Chitosan-AgNPs Composite for C1018 CS in CO2-Saturated 3.5% NaCl Medium under Static and Hydrodynamic Conditions

Rumex vesicarius (RVE) mediated chitosan–AgNPs composite was produced in situ by using an aqueous extract of Rumex vesicarius leaves as the reducing agent to reduce Ag+ to Ag0. The synthesized composite was evaluated as a sweet (CO2) corrosion inhibitor (CI) for C1018 carbon steel (CS) in 3.5 wt% NaCl solution under static and hydrodynamic conditions. The corrosion inhibitive performance was evaluated using electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP) techniques, as well as scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDAX), and atomic force microscopy (AFM) on corroded C1018 CS without and with additives. The effect of concentration, immersion time, temperature, and rotation speed on the CI performance of the composite was also investigated. The corrosion inhibitive effect increased with increasing composite dosage, with the highest inhibition efficiency (IE) acquired at the maximum composite dosage of 0.3%. Beyond this concentration, the IE decline with increasing concentration. Furthermore, IE was found to increase with immersion time and decline with a temperature rise from 25 to 40 �C, with the optimum temperature of 60 �C found to accelerate corrosion without and with RVE-mediated Chi–AgNPs composite. Under high shear stress, the Chi–AgNPs composite exhibits moderate corrosion inhibition under hydrodynamic conditions. The surface analysis results validate the formation of a protective covering due to composite adsorption on the CS surface. The RVE-mediated chitosan–AgNPs composite could be recommended as a CI for C1018 CS in sweet (CO2) corrosion environments at ambient temperatur

PlasmoView: A Web-based Resource to Visualise Global Plasmodium falciparum Genomic Variation

Malaria is a global public health challenge, with drug resistance a major barrier to disease control and elimination. To meet the urgent need for better treatments and vaccines, a deeper knowledge of Plasmodium biology and malaria epidemiology is required. An improved understanding of the genomic variation of malaria parasites, especially the most virulent Plasmodium falciparum (Pf) species, has the potential to yield new insights in these areas. High-throughput sequencing and genotyping is generating large amounts of genomic data across multiple parasite populations. The resulting ability to identify informative variants, particularly single-nucleotide polymorphisms (SNPs), will lead to the discovery of intra- and inter-population differences and thus enable the development of genetic barcodes for diagnostic assays and clinical studies. Knowledge of genetic variability underlying drug resistance and other differential phenotypes will also facilitate the identification of novel mutations and contribute to surveillance and stratified medicine applications. The PlasmoView interactive web-browsing tool enables the research community to visualise genomic variation and annotation (eg, biological function) in a geographic setting. The first release contains over 600 000 high-quality SNPs in 631 Pf isolates from laboratory strains and four malaria-endemic regions (West Africa, East Africa, Southeast Asia and Oceania)

Assessment of the therapeutic efficacy of a paediatric formulation of artemether-lumefantrine (Coartesiane(®)) for the treatment of uncomplicated Plasmodium falciparum in children in Zambia

BACKGROUND: Sentinel site surveillance of antimalarials by in-vivo therapeutic efficacy studies in Zambia is one of the key activities ear-marked for monitoring and evaluation. The studies are conducted annually in order to provide timely and reliable information on the status of the recommended regimens for malaria case management. The findings of the therapeutic efficacy of an artemisinin-based combination therapy of pediatric artemether-lumefantrine (Coartesiane(®)) are reported. METHOD: The design is a simple, one-arm, prospective evaluation of the clinical and parasitological response to directly observed treatment for uncomplicated malaria. The study was conducted in sentinel sites using the WHO standardized protocol for the assessment of therapeutic efficacy of antimalarial drugs (WHO 2000) in children under five years of age, weighing less than 10 Kg. The study was conducted at two clinics, one in Chongwe (Lusaka Province) and Chipata (Eastern Province). The 28-day follow-up period was used coupled with PCR genotyping for MSP1 and MSP2 in order to differentiate recrudescence from re-infections for parasites that appeared after Day 14. RESULTS: 91/111 children enrolled in the study, were successfully followed up. Artemether-lumefantrine (Coartesiane(®)) was found to produce significant gametocyte reduction. The Adequate Clinical and Parasitological Response (ACPR) was found to be 100% (95% CI 96.0;100). CONCLUSION: Coartesiane(® )was effective in treating uncomplicated malaria in Zambian children weighing less than 10 kg, an age group normally excluded from taking the tablet formulation of artemether-lumefantrine (Coartem(®))

PlasmoView: a web-based resource to visualise global Plasmodium falciparum genomic variation.

Malaria is a global public health challenge, with drug resistance a major barrier to disease control and elimination. To meet the urgent need for better treatments and vaccines, a deeper knowledge of Plasmodium biology and malaria epidemiology is required. An improved understanding of the genomic variation of malaria parasites, especially the most virulent Plasmodium falciparum (Pf) species, has the potential to yield new insights in these areas. High-throughput sequencing and genotyping is generating large amounts of genomic data across multiple parasite populations. The resulting ability to identify informative variants, particularly single-nucleotide polymorphisms (SNPs), will lead to the discovery of intra- and inter-population differences and thus enable the development of genetic barcodes for diagnostic assays and clinical studies. Knowledge of genetic variability underlying drug resistance and other differential phenotypes will also facilitate the identification of novel mutations and contribute to surveillance and stratified medicine applications. The PlasmoView interactive web-browsing tool enables the research community to visualise genomic variation and annotation (eg, biological function) in a geographic setting. The first release contains over 600,000 high-quality SNPs in 631 Pf isolates from laboratory strains and four malaria-endemic regions (West Africa, East Africa, Southeast Asia and Oceania)

Drug coverage in treatment of malaria and the consequences for resistance evolution - evidence from the use of sulphadoxine/pyrimethamine

BACKGROUND\ud \ud It is argued that, the efficacy of anti-malarials could be prolonged through policy-mediated reductions in drug pressure, but gathering evidence of the relationship between policy, treatment practice, drug pressure and the evolution of resistance in the field is challenging. Mathematical models indicate that drug coverage is the primary determinant of drug pressure and the driving force behind the evolution of drug resistance. These models show that where the basis of resistance is multigenic, the effects of selection can be moderated by high recombination rates, which disrupt the associations between co-selected resistance genes.\ud \ud METHODS\ud \ud To test these predictions, dhfr and dhps frequency changes were measured during 2000-2001 while SP was the second-line treatment and contrasted these with changes during 2001-2002 when SP was used for first-line therapy. Annual cross sectional community surveys carried out before, during and after the policy switch in 2001 were used to collect samples. Genetic analysis of SP resistance genes was carried out on 4,950 Plasmodium falciparum infections and the selection pressure under the two policies compared.\ud \ud RESULTS\ud \ud The influence of policy on the parasite reservoir was profound. The frequency of dhfr and dhps resistance alleles did not change significantly while SP was the recommended second-line treatment, but highly significant changes occurred during the subsequent year after the switch to first line SP. The frequency of the triple mutant dhfr (N51I,C59R,S108N) allele (conferring pyrimethamine resistance) increased by 37% - 63% and the frequency of the double A437G, K540E mutant dhps allele (conferring sulphadoxine resistance) increased 200%-300%. A strong association between these unlinked alleles also emerged, confirming that they are co-selected by SP.\ud \ud CONCLUSION\ud \ud The national policy change brought about a shift in treatment practice and the resulting increase in coverage had a substantial impact on drug pressure. The selection applied by first-line use is strong enough to overcome recombination pressure and create significant linkage disequilibrium between the unlinked genetic determinants of pyrimethamine and sulphadoxine resistance, showing that recombination is no barrier to the emergence of resistance to combination treatments when they are used as the first-line malaria therapy

Polymorphisms in Plasmodium falciparum chloroquine resistance transporter and multidrug resistance 1 genes: parasite risk factors that affect treatment outcomes for P. falciparum malaria after artemether-lumefantrine and artesunate-amodiaquine.

Adequate clinical and parasitologic cure by artemisinin combination therapies relies on the artemisinin component and the partner drug. Polymorphisms in the Plasmodium falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) genes are associated with decreased sensitivity to amodiaquine and lumefantrine, but effects of these polymorphisms on therapeutic responses to artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) have not been clearly defined. Individual patient data from 31 clinical trials were harmonized and pooled by using standardized methods from the WorldWide Antimalarial Resistance Network. Data for more than 7,000 patients were analyzed to assess relationships between parasite polymorphisms in pfcrt and pfmdr1 and clinically relevant outcomes after treatment with AL or ASAQ. Presence of the pfmdr1 gene N86 (adjusted hazards ratio = 4.74, 95% confidence interval = 2.29 - 9.78, P < 0.001) and increased pfmdr1 copy number (adjusted hazards ratio = 6.52, 95% confidence interval = 2.36-17.97, P < 0.001 : were significant independent risk factors for recrudescence in patients treated with AL. AL and ASAQ exerted opposing selective effects on single-nucleotide polymorphisms in pfcrt and pfmdr1. Monitoring selection and responding to emerging signs of drug resistance are critical tools for preserving efficacy of artemisinin combination therapies; determination of the prevalence of at least pfcrt K76T and pfmdr1 N86Y should now be routine