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Open Access
Water-borne bacterial pathogens in surface waters of Nairobi River and health implication to communities downstream Athi River
(Mount Kenya University, 2013-03) ABEDNEGO M. MUSYOKI, ABEDNEGO M.; SULEIMAN, MBARUK A.; MBITHI, JOHN N.; MAINGI, JOHN M.
The quality of surface water in Nairobi River and the adjacent river Athi was assessed to ascertain whether it meets local and international microbiological standards for safe human consumption. Standard bacteriological techniques were used to describe bacteria content from water samples collected from the two confluent sources. The waters were highly contaminated with human pathogenic bacteria. The most dominant bacteria in combined waters of the two rivers was Escherichia coli (1.0 x 104 ± 2.6 x 103 / 100 mL) while the least was Shigella flexneri (1.2 x 101 ± 1.2 x 101 / 100 mL). Other bacteria were Klebsiella aerogenes (7.4 x 101 ± 1.8 x 101 / 100 mL), Enterococcus faecalis (3.6 x 103 ± 3.2 x 103 / 100 mL), Salmonella typhi (2.1 x 102 ± 1.3 x 102 / 100 mL), Pseudomonas aeruginosa (6.5 x 102 ± 1.1 x 102 / 100 mL), Salmonella paratyphi (1.6 x 101 ±1.1 x 101 / 100 mL), and Vibrio cholerae (5.6 x 102 ± 1.0 x 102 / 100 mL). Microbiological quality of the surface water was unacceptably high above compliance level of national standards, and the World Health Organization (WHO) guidelines for drinking water and agricultural use. The water from these rivers is not potable, and poses a health risk to communities that rely on the rivers as primary sources of domestic and subsistence irrigation use. These findings in water scarce region of the world underline the challenges a number of developing countries are facing currently and in long-term into the future. Lessons learnt in this study would suggest appropriate measures are necessary to control pollution of similar rivers in sub-Saharan regions in particular and developing countries in general to ensure availability of clean water supplies to large concentrated populations in cities within the Millennium Development Goals.
Open Access
Diurnal and seasonal variations of pathogenic bacteria in Dandora Sewage Treatment Plant wastewater, Nairobi, Kenya
(International Research Journals, 2013-02) Musyoki, Abednego M.; Suleiman, Mbaruk A.; Mbithi, John N.; Maingi, John M.
Diurnal and seasonal variation of pathogenic bacteria diversity and loads at Dandora Sewage Treatment Plant (DSTP), and compliance of effluent with local and international statutory requirements was assessed. Standard bacteriological techniques were used to describe bacteria content from wastewater samples collected from influent and effluent sources. Diurnal variation of bacterial loads occurred only in the effluent (F ꞊ 22.788, p ꞊ 0.000) with lower counts in the afternoon. Seasonal variation was observed in both influent (F ꞊ 14.795, p ꞊ 0.001) and the effluent (F ꞊ 23.574, p = 0.000), with more pollution during the dry season. The effluent microbiological quality, irrespective of diurnal and seasonal changes, did not adhere to local and international statutory requirements for discharge into natural environment. The effluents were polluted with pathogens including; Escherichia coli, Enterococcus faecalis, Staphylococcus typhi, Pseudomonas aeruginosa, and Klebsiella aerogenes. The health risk posed to downstream users of DSTP effluent occurs notwithstanding the time of the day or season. The findings in this study suggest need for appropriate measures to monitor and control the microbiological quality of DSTP effluent and other similar facilities in sub-Saharan Africa, to ensure public health safety in line with the millennium Development Goals.
Open Access
Levels of Adherence to Coartem© in the Routine Treatment of Uncomplicated Malaria in Children Aged Below Five Years, in Kenya.
(Iranian Journal of Public Health, 2013) Ogolla, Jared Otieno; Ayaya, Samuel Omulando; Otieno, Christina Agatha
This study sought to determine the level of adherence to Coartem© in the routine treatment of uncomplicated malaria among children under the age of five years in Nyando district, Kenya. Seventy-three children below the age of five years with microscopically confirmed uncomplicated Plasmodium falciparum malaria and prescribed Coartem(®) during the normal outpatient department hours were included into the study on 27(th) of April to 15(th) of May 2009. Adherence was assessed through a semi-structured interviewer administered questionnaire; pill count and blister pack recovery. Patients were then classified into three categories of adherence. Patients who had tablets remaining in the blister pack were classified as definitely non-adherent. Those who had blister pack missing or empty and the caretaker did not report administering all the doses at the correct time and amount were considered probably non-adherent or as probably adherent when the caretaker reported administering all doses at the correct time and amount. Nine (14.5%) patients were definitely non-adherent, 6 (9.7%) probably non-adherent and 47 (75.8%) probably adherent. The most significantly left tablet was the sixth doses (P = 0.029). Caretakers should be made much aware that non-adherence might not only be dangerous to child's health but also dramatically increase the financial cost for public-health services.
Open Access
An Analysis of Uptake in HIV Voluntary Counselling and Testing Services: Case of Mount Kenya University Students, Kenya
(International Knowledge Sharing Platform, 2013-04) Museve, Judith; Gongera, Enock George; Labongo, Constantine Loum
Early testing for HIV/AIDS offers many benefits for young people but in many countries it is still rare. Where services are still fairly low as in Kenya, people may feel that the risks of knowing and disclosing their sero-status outweigh the benefits; hence one important challenge in addressing the needs of young people lies in understanding the extent to which the young people know about and use protective measures against the risks. VCT is a key intervention in HIV prevention. Being a prevention program VCT seeks to initiate behaviour change yet its uptake is still wanting. Data from the Mount Kenya University HIV/AIDS open day carried out at the main campus in 2010 by LVCT showed that only 18.4% of the students had VCT. Currently, despite 90% of HIV prevention programs targeting the youth, VCT is not taken by all. The rate of HIV VCT among the youth is persistently low with studies showing that only a small proportion of youth have undergone VCT in Kenya. Although there is high awareness among the youth with majority acknowledging the importance of VCT, there was need to investigate the low uptake of VCT amongst university students. From the Kenya National AIDS Strategic Plan 2005/6 - 2009/10, the national target of having 80% of the population being tested by the year 2010 is yet to be achieved. This makes it necessary to assess the uptake of VCT from time to time and explore ways of increasing its uptake. The study employed a cross sectional survey that was conducted among Mount Kenya University students in Thika district. Multi-stage sampling was used to pick the respondents. Only schools and departments with students from year 1 to year 4 of study were considered. The number of participating students from schools and departments were predetermined by population proportionate allocation with individual study subjects being picked using a table of random numbers. A sample size of 283 respondents was used as determined by Fischer et al equation with the expected VCT uptake of 28%. The data was collected using questionnaires and focus group discussions from October to November, 2011. Processing of data was carried out using the Statistical Package for Social Scientists (SPSS Version 16). Descriptive statistics and frequency tables were used to describe the characteristics of participants while chi-square test was used to test association between dependent variables (knowledge, perception, socio-economic, school-based and programmatic factors) and independent variable (Level of uptake). The data was summarized in tables; and presented using graphs and charts. Odds ratio with 95% confidence intervals was used to show associations and p-value <0.05 was considered a statistically significant level of precision. Qualitatitive data fom FGDs was recorded on note books and content analysis technique was used to summarize the findings . Uptake of VCT services was categorized into two: Uptake (at least one visit ) and no uptake ( no visit). The uptake of VCT services among MKU students is 76% with the three leading reasons for uptake being “To satisfy curiosity”, “To seek early treatment” and “To determine a partner’s degree of faithfulness”. Leading reasons for non-uptake of VCT services are “Fear of a positive result”, “Fear of people finding out” and “Not feeling at risk”. Knowledge of VCT is quite high at 80% with the most common sources of first VCT information being radio, television and open forums. Mothers and Nutrition counseling are important in influencing the uptake of VCT by the students. Majority of the students perceive VCT to be important in the fight against HIV. Majority of the students have a positive attitude toward VCT with over 80% of them willing to go for the service. Age affected VCT uptake with older students being more likely to go for VCT. Religion was associated with VCT uptake with majority of the students who went for VCT being protestant or catholic. School-based factors that influence VCT uptake among MKU students are type of course one is studying and year of study; with the final year students having the highest rate of uptake of VCT while pharmacy students have the lowest rate of VCT uptake. The key programmatic factors that influence VCT uptake are quality of services, location and appearance of VCT center. From the findings of this study, there is need to review the design and location of VCT centers targeting the youth to make them more youth friendly. Mount Kenya University can improve VCT service delivery by having the entire health unit staff trained in VCT. This will enable them to provide the service on demand.
Open Access
Reliability of Mid-Upper Arm Circumference Measurements Taken by Community Health Nurses
(Current Research in Nutrition and Food Science Journal, 2015-04) Saeed, Hibbah Araba; Mogendi, Joseph Birundu; Akparibo, Robert; Kolsteren, Patrick
Mid upper arm circumference-based diagnosis of severe acute malnutrition is seen as very attractive because it is assumed to be simple to use in measuring the arm and also requires a single cut-off without having to compute an index or compare to a reference population. The circumference of the left upper arm measured at the mid-point between the tip of the shoulder and the tip of the elbow is referred to as mid upper arm circumference (MUAC). MUAC was originally used in emergency settings where huge populations had to be screened within a short time. However, in the past few years the development of community therapeutic care of acute malnutrition implied a need for a diagnostic tool. The general objective of the study was to assess the inter- and intra-observer variability in MUAC measurements of under-five children by community health nurses in selected communities of the Northern Region in Ghana. A community-based cohort study was conducted on a convenience sample of 120 community health nurses and nursing students from selected communities in the Northern region of Ghana. Each CHN measured MUAC for four unique children on three consecutive days to assess intra-observer variability. To assess inter-observer variability, 50 independent nursing students took MUAC measures of four children on the same day. Bland Altman plots showed a high degree of agreement of MUAC measures taken repeatedly for three days by the same observers and ICC= 0.993. MUAC measures among observers (inter-observer) and ICC =0.042 showed a considerable level of variability among different observers. This study showed that MUAC is reliable when repeated measures are taken on children by the same observers, but using different observers for the same children showed a high level of variability.
Open Access
Polyphenols and free radical Scavenging Properties of Kenyan Tea Seed Oil Cake
(International Journal of Research in Chemistry and Environment, 2013-04) Njuguna, D.G.; Wanyoko, J.K; Kinyanjui, T; Wachira, F.N
Studies were conducted on the polyphenolic content, individual and total catechins and the free radical scavenging capacities in the tea seed oil cake of six selected tea cultivars of Kenya. Total polyphenolic content was analyzed by use of UV-Visible spectrometer with Gallic acid as the standard. Individual catechins were analyzed by use of Reverse Phase-Higher Performance Liquid Chromatography. Free radical scavenging capacity was measured by UV-Visible spectrophotometer and using 2,2- diphenyl-1-picrylhydrazyl (DPPH) as a free stable radical. Tea seed oil cake contained polyphenols and catechins which were in the range of 1.03-2.60% and 0.66-1.40% respectively. Individual catechins results were as follows, EGC was in the range of 0.067- 0.086%, +C was in the range of 0.019-0.024%, EC was in the range of 0.025-0.063%, EGCG was in the range of 0.402-0.883% and finally ECG was in the range of 0.113-0.409%. The antioxidant activity of tea seed cake was evaluated by scoring the percent free radical scavenging activity which ranged from 8-16%. From these results tea seed oil cake is rich in polyphenols and catechins that contribute the found antioxidant activities.
Open Access
Immunotherapeutic treatment of HIV-1: review of safety and efficacy
(Researcg Gate, 2016-02-16) Kariuki, SM; Musyoki, SK; Kemoi, EK
Background: For over two decades, the treatment of HIV-1 patients has relied on antiretroviral (ART). These drugs have had a great deal of achievement in not only controlling the viral load but also partly reconstituting the immune system in HIV-1 infected persons. However, the misfortune is that ART is a lifelong treatment because it cannot achieve complete eradication of HIV-1 virus, yet with its side effects like many other drugs. Scientists have hence introduced immunotherapy in an effort toward complete eradication of HIV-1 in HIV/AIDS patients. Objective: The aim of this paper was to determine the effectiveness and safety of the various immunotherapy formats used in the treatment of HIV-1 infection. Method: We reviewed a number of peer-reviewed published articles to determine the effectiveness and safety of the different immunotherapy formats tested in randomized clinical trials and animal model experiments. Results: Majority of immunotherapy regimens used in combination with ART to treat HIV-1 positive human or animals were found to be effective in boosting the cell-mediated immune responses in HIV-1 infection but achieved insignificant results in controlling the viral load in these experiments. Most of the immunotherapy formats were also well tolerated recording minimal to no adverse effects on HIV-1 patients. Conclusion: Most immunotherapy agents are relatively effective and safe when used in combination with ART in modulating immune response to HIV-1. These immunotherapy agents do not significantly reduce the viral load and hence cannot eliminate HIV-1.
Open Access
Knowledge, attitudes and practice on micronutrients deficiencies among parents and caregivers of under fives in Gatung'ang'a Location, Mathira West, Nyeri County.
(Mount Kenya University, 2014-10-21) Njogu, Patrick KInyanjui
Open Access
Mapping of DBLα Sequence Tags of Field Isolates from Two Malaria Endemic Sites in Kenya
(Journal of Natural Sciences Research, 2015) Makokha, Francis W.; Bull, Peter C.; Kimani, Francis T.; Hungu, Charity; Shaviya, Nathan; Magoma, Gabriel; Ahmed, Sabah O.
Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) found on the surface of infected erythrocytes (IEs) mediate antigenic variation during P. falciparum infection enabling the parasite evade host immune responses and prolong infection. These molecules mediate binding of IEs to host endothelial cells and uninfected erythrocytes. Cytoadhesion of IE to host cells leads to sequestration in tissues and PfEMP1 is thought to play an important role in parasite virulence. Here we analysed 1725 sequence tags sampled from the DBLa region of PfEMP1 encoding “var” genes from 27 patients in two different geographical regions in Kenya, Mbita in Western Kenya and Twiga on the Kenyan coast. The objective of this study was to construct a network to assess the extent of shared position specific polymorphic blocks (PSPBs) in sequences isolated from genomic DNA of field isolates from the two malaria endemic sites in Kenya. Sequences from Mbita study site and those from Tiwi largely clustered into separate giant networks with only a limited number of sequences from the two sites linking to each other. This observation suggests that the parasite populations from the two endemic sites could be genetically varied and that PfEMP1 sequencing could be a useful tool of understanding the genetics of parasite populations. Thus the network approach of studying relationships between DBLα sequences is a useful tool of uncovering the genetic structure of parasite populations circulating in different malaria endemic regions.
Open Access
Fitness cost of resistance for lumefantrine and piperaquine-resistant Plasmodium berghei in a mouse model
(Gimode et al. Malaria Journal, 2015) Gimode, Winnie R; Kiboi, Daniel M; Kimani, Francis T; Wamakima, Hannah N; Burugu, Marion W; Muregi, Francis W
Background: The evolution of drug-resistant parasites is a major hindrance to malaria control, and thus understanding the behaviour of drug-resistant mutants is of clinical relevance. The study aimed to investigate how resistance against lumefantrine (LU) and piperaquine (PQ), anti-malarials used as partner drugs in artemisinin-based combination therapy (ACT), impacts parasite fitness. This is important since resistance to ACT, the first-line anti-malarial regimen is increasingly being reported.
Open Access
Novel Rational Drug Design Strategies with Potential to Revolutionize Malaria Chemotherapy
(Bentham Science Publishers Ltd., 2011) Muregi, F. W.; Kirira, P. G.; Ishih, A.
Efforts to develop an effective malaria vaccine are yet to be successful and thus chemotherapy remains the mainstay of malaria control strategy. Plasmodium falciparum, the parasite that causes about 90% of all global malaria cases is increasingly becoming resistant to most antimalarial drugs in clinical use. This dire situation is aggravated by re- ports from Southeast Asia, of the parasite becoming resistant to the “magic bullet” artemisinins, the last line of defense in malaria chemotherapy. Drug development is a laborious and time consuming process, and thus antimalarial drug discov- ery approaches currently being deployed largely include optimization of therapy with available drugs—including combi- nation therapy and developing analogues of the existing drugs. However, the latter strategy may be hampered by cross- resistance, since agents that are closely related chemically may share similar mechanisms of action and/or targets. This may render new drugs ineffective even before they are brought to clinical use. Evaluation of drug-resistance reversers (chemosensitizers) against quinoline-based drugs such as chloroquine and mefloquine is another approach that is being explored. Recently, evaluation of new chemotherapeutic targets is gaining new impetus as knowledge of malaria parasite biology expands. Also, single but hybrid molecules with dual functionality and/or targets have been developed through ra- tional drug design approach, termed as “covalent bitherapy”. Since desperate times call for radical measures, this review aims to explore novel rational drug-design strategies potentially capable of revolutionizing malaria therapy. We thus ex- plore malaria apoptosis machinery as a novel drug target, and also discuss the potential of hybrid molecules as well as prodrugs and double prodrugs in malaria chemotherapy.
Open Access
Electrochemical deallylation of apha-allyl cyclic amines and synthesis of optically active quaternary cyclic amino acids
(PubMED, 2010-04) Kirira, P. G.; Kuriyama, M.; Onomura, O.
Open Access
Anti-parasitic activity and cytotoxicity of selected medicinal plants from Kenya
(Journal of Ethnopharmacology, 2009-06-25) Kigondu, EV; Rukunga, GM; Keriko, Joseph M.
Indigenous rural communities in the tropics manage parasitic diseases, like malaria and leishmaniasis, using herbal drugs. The efficacy, dosage, safety and active principles of most of the herbal preparations are not known. Extracts from 6 selected plant species, used as medicinal plants by indigenous local communities in Kenya, were screened for in vitro anti-plasmodial and anti-leishmanial activity, against 2 laboratory-adapted Plasmodium falciparum isolates (D6, CQ-sensitive and W2, CQ-resistant) and Leishmania major (IDU/KE/83 = NLB-144 strain), respectively. The methanol extract of Suregada zanzibariensis leaves exhibited good anti-plasmodial activity (IC50 4.66 ± 0.22 and 1.82 ± 0.07 μg/ml for D6 and W2, respectively). Similarly, the methanol extracts of Albizia coriaria (IC50 37.83 ± 2.11 μg/ml for D6) and Aspergillus racemosus (32.63 ± 2.68 and 33.95 ± 2.05 μg/ml for D6 and W2, respectively) had moderate anti-plasmodial activity. Acacia tortilis (IC50 85.73 ± 3.36 μg/ml for W2) and Albizia coriaria (IC50 71.17 ± 3.58 μg/ml for W2) methanol extracts and Aloe nyeriensis var kedongensis (IC50 87.70 ± 2.98 and 67.84 ± 2.12 μg/ml for D6 and W2, respectively) water extract exhibited mild anti-plasmodial activity. The rest of the extracts did not exhibit any anti-plasmodial activity. Although the leishmanicidal activity of extracts were lower than for pentosam (80%), reasonable activity was observed for Aloe nyeriensis methanol (68.4 ± 6.3%), Albizia coriara water (66.7 ± 5.0%), Maytenus putterlickoides methanol (60.0 ± 6.23%), Asparagus racemosus methanol and water (58.3 ± 8.22 and 56.8 ± 6.58%, respectively), Aloe nyeriensis water (53.3 ± 5.1%) and Acacia tortilis water (52.9 ± 6.55%) extracts at 1000 μg/ml. Leishmania major infected macrophages treated with methanol extracts of Suregada zanzibariensis and Aloe nyeriensis var kedongensis and Pentostam® had infection rates of 28 ± 2.11, 30 ± 1.22 and 40 ± 3.69%, respectively at 1000 μg/ml, indicating better anti-leishmanial activity for the extracts. The methanol extract of Albizia coriara (44.0 ± 3.69%) and aqueous extracts of Asparagus racemosus (42 ± 3.84%) and Acacia tortilis (44 ± 5.59%) had similar activity to pentosam®. Multiplication indices for Leishmania major amastigotes treated with methanol extracts of Albizia coriaria, Suregada zanzibariensis and Aloe nyeriensis var kedongensis, aqueous extract of Acacia tortilis and pentosam® were 28.5 ± 1.43, 29.4 ± 2.15, 31.1 ± 2.22, 35.9 ± 3.49 and 44.0 ± 3.27%, respectively, at 1000 μg/ml, confirming better anti-leishmanial activity for the extracts. Aqueous extracts of Aloe nyeriensis (46.7 ± 3.28%) and Albizia coriaria (47.5 ± 3.21%) had similar activity level to pentosam®. The plant extracts have better inhibitory activity while pentosam® has better leishmanicidal activity. All extracts exhibited very low cytotoxicity (CC50 > 500 μg/ml) against human embryonic lung fibroblast (HELF) cells. The investigations demonstrated the efficacy and safety of some extracts of plants that are used by rural indigenous communities for the treatment of parasitic diseases.
Open Access
Drug Sensitivity Testing Using Counter Diffusion Technique on Methicilin-Resistant Staphylococcus aureus in Clinical Isolates within selected Hospitals in Nakuru County
(International Journal of Science and Research, 2013) Owino, O. J.; Onyuka, O. H. Jackson; Kinge, Waithaka S.
Several infectious bacterial strains have acquired resistance towards most available antibiotics and it’s for this reason that, there is need to study drug sensitivity using counter diffusion technique for methicillin-resistant Staphylococcus aureus in isolates so that combination therapy can be embraced since the core factor in using the method is the ability to give good synergistic potential among the drugs. The specific objective was to find out the susceptibility pattern for the MRSA organism using the disc diffusion and compare it to the counter diffusion technique. This was a cross sectional study design and simple random sampling was used to select patients to be surveyed from each of the randomly selected six hospitals. A total of 423 samples were used. A standard laboratory technique was used in the study and MRSA screen test and sensitivity testing were also used. The MRSA was 100 % resistant to licomycin, gentamycine and negative control and 100% sensitive to vancomycin and counter diffusion technique. Duncan Multiple Range Test established that lincomycin, gentamycin and the negative control did not show any significant differences between them, but they varied significantly with the positive control and the counter diffusion treatments. Positive control and counter diffusion also varied significantly. No child was resistant. A comparison of the susceptibility pattern for the MRSA organism using disc diffusion and counter diffusion technique indicated that the mean zone of inhibition using the counter diffusion technique was 27.1mm and was significantly higher than the zones of inhibition by either lincomycin p-0.0001, or gentamycin p<0.0001
Open Access
PfEMP1 DBLα Sequence Tags in Genomic DNA of P. falciparum Field Isolates from Two Malaria Endemic Sites in Kenya
(Journal of Natural Sciences Research, 2015) Makokha, Francis W.; Omar, Sabah A.; Kimani, Francis T.; Magoma, Gabriel; Udu, Rahma
Background Malaria caused by Plasmodium falciparum remains a major cause of childhood morbidity and mortality in sub- Saharan Africa. PfEMP1 protein, coded for by a family of about sixty variant var genes, is a parasite protein found on infected erythrocyte membrane. PfEMP1 protein mediates cytoadherence of infected erythrocytes on endothelial cells which may lead to severe symptoms of malaria. Although PCR amplification of the whole gene is difficult due to high variability, primers targeting the DBLα domain have been designed and used to study pfemp1 genes. This objective of this study was to establish the distribution of DBLα sequence tags in isolates of Plasmodium falciparum from two malaria endemic sites in Kenya. Methods DNA extracted from field isolates collected from Mbita (Western Kenya) and Tiwi (Coastal region) was used to isolate and amplify DBLα domain sequence tags of pfemp1 by PCR. PCR products were sequenced by 454 next generation sequencing. After assembly, the translated protein sequences (GenBank KP085750-KP087726) were then aligned in Mega 5.2 and classified into cys/PoLV groups based on the number of cysteine residues and the motifs at PoLV1 and PoLV2 within the sequence tag. Six sequence groups were found in sequences from both endemic sites. Group 4 sequences were the most prevalent (57.35% and 57.07% in isolates from Mbita and Tiwi respectively) in the isolates from both sites. Sequence tags from Tiwi had a higher proportion of cys2 (group 1 and 2) than sequences from Mbita although individual group 2 sequence tags were slightly higher in Mbita tags. Similarly the proportion of groups 5 and 6 sequence tags was higher in sequence tags from Tiwi than those from Mbita. Conclusion In conclusion, the frequency of the different cyc/PoLV groups of DBLα sequence tags at both endemic sites follow almost similar pattern with group four sequence tags being the majority among the sequence tags isolated from patient isolates from both study sites. However, in the absence of expression data, the impact of this genomic distribution pattern on malaria pathology remains unknown. Key Words: Malaria, PfEMP1, cys/PoLV, DBLα, var, Sequence tags
Open Access
Resistance of a rodent malaria parasite to a thymidylate synthase inhibitor induces an apoptotic parasite death and imposes a huge cost of fitness.
(PubMedCentral, 2011-06-16) Muregi, Francis W.; Ohta, Isao; Masato, Uchijima; Kino, Hideto; Ishih, Akira
BACKGROUND: The greatest impediment to effective malaria control is drug resistance in Plasmodium falciparum, and thus understanding how resistance impacts on the parasite's fitness and pathogenicity may aid in malaria control strategy. METHODOLOGY/PRINCIPAL FINDINGS: To generate resistance, P. berghei NK65 was subjected to 5-fluoroorotate (FOA, an inhibitor of thymidylate synthase, TS) pressure in mice. After 15 generations of drug pressure, the 2% DT (the delay time for proliferation of parasites to 2% parasitaemia, relative to untreated wild-type controls) reduced from 8 days to 4, equalling the controls. Drug sensitivity studies confirmed that FOA-resistance was stable. During serial passaging in the absence of drug, resistant parasite maintained low growth rates (parasitaemia, 15.5%±2.9, 7 dpi) relative to the wild-type (45.6%±8.4), translating into resistance cost of fitness of 66.0%. The resistant parasite showed an apoptosis-like death, as confirmed by light and transmission electron microscopy and corroborated by oligonucleosomal DNA fragmentation. CONCLUSIONS/SIGNIFICANCE: The resistant parasite was less fit than the wild-type, which implies that in the absence of drug pressure in the field, the wild-type alleles may expand and allow drugs withdrawn due to resistance to be reintroduced. FOA resistance led to depleted dTTP pools, causing thymineless parasite death via apoptosis. This supports the tenet that unicellular eukaryotes, like metazoans, also undergo apoptosis. This is the first report where resistance to a chemical stimulus and not the stimulus itself is shown to induce apoptosis in a unicellular parasite. This finding is relevant in cancer therapy, since thymineless cell death induced by resistance to TS-inhibitors can further be optimized via inhibition of pyrimidine salvage enzymes, thus providing a synergistic impact. We conclude that since apoptosis is a process that can be pharmacologically modulated, the parasite's apoptotic machinery may be exploited as a novel drug target in malaria and other protozoan diseases of medical importance.
Open Access
Next-Generation Antimalarial Drugs: Hybrid Molecules as a New Strategy in Drug Design
(Department of Infectious Diseases, Hamamatsu University School of Medicine, Hamamatsu, Japan. 2 Centre for Biotechnology Research and Development, Kenya Medical Research Institute (KEMRI) Nairobi, Kenya),, 2010) Muregi, Francis W.; Ishih, Akira
Malaria is a disease that affects nearly 40% of the global population, and chemotherapy remains the mainstay of its control strategy. The global malaria situation is increasingly being exacerbated by the emergence of drug resistance to most of the available antimalarials, necessitating search for novel drugs. A recent rational approach of antimalarial drug design characterized as ‘‘covalent bitherapy’’ involves linking two molecules with individual intrinsic activity into a single agent, thus packaging dualactivity into a single hybrid molecule. Current research in this field seems to endorse hybrid molecules as the next-generation antimalarial drugs. If the selective toxicity of hybrid prodrugs can be demonstrated in vivo with good bioavailability at the target site in the parasite, it would offer various advantages including dosage compliance, minimized toxicity, ability to design better drug combinations, and cheaper preclinical evaluation while achieving the ultimate object of delaying or circumventing the development of resistance. This review is focused on several hybrid molecules that have been developed, with particular emphasis on those deemed to have high potential for development for clinical use. Drug Dev Res 71:20–32, 2010
Open Access
Antimalarial Drugs and their Useful Therapeutic Lives: Rational Drug Design Lessons from Pleiotropic Action of Quinolines and Artemisinins
(Department of Infectious Diseases, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashiku, Hamamatsu 431-3192, Japan, 2011) Muregi, Francis W.
Efforts to develop an effective malarial vaccine are yet to be successful and thus chemotherapy remains the mainstay of malaria control strategy. Unfortunately, Plasmodium falciparum, the parasite that causes about 90% of all global malaria cases is increasingly becoming resistant to classical antimalarials, necessitating a search for new chemotherapeutics preferably with novel modes of action. Today, rational drug discovery strategy is gaining new impetus as knowledge of malaria parasite biology expands, aided by the parasite genome database and improved bioinformatics tools. Drug development is a laborious, time consuming and costly process, and thus the “useful therapeutic lives” (UTLs) of new drugs should be commensurate with the resources invested in their development. Historical evidence on development and evolution of resistance to classical antimalarial drugs shows that the mode of action of a drug influences its UTL. Drugs that target single and specific targets such as antimalarial antifolates and atovaquone (ATQ) are rendered ineffective within a short time of their clinical use, unlike drugs with pleiotropic action such as chloroquine (CQ) and artemisinins (ART) with long UTLs. Unfortunately, almost all new targets currently being explored for development of novel drugs belong to the “specific target” other than the “multiple target” category, and is plausible that such drugs will have short UTLs. This review relates the pleiotropic action of CQ and ART with their long UTLs, and discusses their relevance in rational drug development strategies. Novel targets with potential to yield drugs with long UTLs are also explored.
Open Access
Plasmodium berghei: efficacy of 5- fluoroorotate in combination with commonly used antimalarial drugs in a mouse model
(PubMed, 2009) Muregi, Francis W.; Kino, K. Kino; Ishih, A.; Kino, H.
information Abstract Resistance to antimalarial antifolates necessitates a search for new antimetabolites targeting other enzymes of the folate metabolic pathway. In this study, 5-fluoroorotate (FOA), reported to be an inhibitor of thymidylate synthase, was assayed against Plasmodium berghei NK 65 in mice, with(out) an oral uridine supplement. FOA (2.5 and 5.0 mg/kg bw.) was tested alone, or in a double and triple combination with a fixed oral dose of 1.25 and 2.5 mg/kg of pyrimethamine (PYR); 1.0 and 2.0 mg/kg of dapsone (DAP); 1.0 and 2.0 mg/kg of artesunate (ART). FOA achieved high suppression which ranged from 95.7% to aparasitaemic, activity that was dosedependent. At the highest dosages used, FOA-PYR and FOA-DAP-ART combinations were synergistic with 100% cure rate, while FOA-PYR-ART was antagonistic. Drugs in a synergistic combination may exert less resistance selection pressure, thus FOA-PYR and FOA-DAP-ART warrant further evaluation with an ultimate object of possible clinical use against drug-resistant malaria.
Open Access
Possible involvement of IFN-gamma in early mortality of Plasmodium berghei NK65-infected BALB/c mice after febrifugine treatment.
(Southeast Asian J Trop Med Public Health, 2008) Ishih, A.; Nagata, T.; Kobayashi, F.; Muregi, Francis W.; Ohori, K.; Miyase, T.
Parasitemia patterns, survival and cytokine levels of Plasmodium berghei NK65-infected BALB/c mice, treated orally with the alkaloidal mixture of febrifugine and isofebrifugine at a dose of 1 mg/kg twice a day for 4 consecutive days were monitored. Whereas the untreated mice showed a progressive increase in parasitemia and ultimate death, the alkaloid mixture-treated group showed a transient suppression of parasitemia during the course of treatment. However, the parasitemia increased on discontinuation of treatment, leading to earlier death of mice in the treated group than in the infected but untreated controls. Mice in the infected but untreated group displayed a significant elevation in serum IFN-gammay levels during the first week post-infection (pI) and from Day 14 pI, relative to the levels in the uninfected controls. In contrast, although mice in the alkaloid mixture-treated group displayed no significant elevation in serum IFN-gamma levels during the first week pI, they showed considerable levels on Day 14 pI. There were no significant differences in serum IL-4 levels among the groups. The titers of the parasite-specific IgG1, IgG2a, IgG2b and IgG3 were significantly elevated from Day 11 pI in both the treated and untreated groups. There was a significant difference in survival duration between the IFN-gamma-/- mutant and BALB/c mice. IFN-gamma-/- mutant mice showed a decrease in parasitemia levels while receiving medication, which was significantly lower than those of the treated BALB/c mice. The results of the present study suggest that although IFN-gamma is significant for protective immunity in mice with malaria infection, it may play an adverse role post-medication, causing earlier mortality of treated BALB/c mice.