Displaying publications 81 - 100 of 308 in total

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  1. Fulltext Molecular Surveillance of Pfkelch13 and Pfmdr1 Mutations in Plasmodium falciparum Isolates from Southern Thailand
    Khammanee T, Sawangjaroen N, Buncherd H, Tun AW, Thanapongpichat S
    Korean J Parasitol, 2019 Aug;57(4):369-377.
    PMID: 31533403 DOI: 10.3347/kjp.2019.57.4.369
    Artemisinin-based combination therapy (ACT) resistance is widespread throughout the Greater Mekong Subregion. This raises concern over the antimalarial treatment in Thailand since it shares borders with Cambodia, Laos, and Myanmar where high ACT failure rates were reported. It is crucial to have information about the spread of ACT resistance for efficient planning and treatment. This study was to identify the molecular markers for antimalarial drug resistance: Pfkelch13 and Pfmdr1 mutations from 5 provinces of southern Thailand, from 2012 to 2017, of which 2 provinces on the Thai- Myanmar border (Chumphon and Ranong), one on Thai-Malaysia border (Yala) and 2 from non-border provinces (Phang Nga and Surat Thani). The results showed that C580Y mutation of Pfkelch13 was found mainly in the province on the Thai-Myanmar border. No mutations in the PfKelch13 gene were found in Surat Thani and Yala. The Pfmdr1 gene isolated from the Thai-Malaysia border was a different pattern from those found in other areas (100% N86Y) whereas wild type strain was present in Phang Nga. Our study indicated that the molecular markers of artemisinin resistance were spread in the provinces bordering along the Thai-Myanmar, and the pattern of Pfmdr1 mutations from the areas along the international border of Thailand differed from those of the non-border provinces. The information of the molecular markers from this study highlighted the recent spread of artemisinin resistant parasites from the endemic area, and the data will be useful for optimizing antimalarial treatment based on regional differences.
    Matched MeSH terms: Plasmodium falciparum/drug effects; Plasmodium falciparum/genetics*; Plasmodium falciparum/isolation & purification
  2. Therapeutic equivalence of a low dose artemisinin formulation in falciparum malaria patients
    Wong JW, Yuen KH, Nagappan S, Shahul WS, Ho SS, Gan EK, et al.
    J Pharm Pharmacol, 2003 Feb;55(2):193-8.
    PMID: 12631411
    We have evaluated the therapeutic equivalence of a beta-cyclodextrin-artemisinin complex at an artemisinin dose of 150 mg, with a commercial reference preparation, Artemisinin 250 at a recommended dose of 250 mg. One hundred uncomplicated falciparum malarial patients were randomly assigned to orally receive either beta-cyclodextrin-artemisinin complex (containing 150 mg artemisinin) twice daily for five days or the active comparator (containing 250 mg artemisinin) twice daily for five days. The patients were hospitalized for seven days and were required to attend follow up assessments on days 14, 21, 28 and 35. All patients in both treatment groups were cured of the infection and achieved therapeutic success. At day seven of treatment, all patient blood was clear of the parasites and the sublingual temperature of all patients was less than 37.5 degrees C. Moreover, the parasite clearance time in both treatment groups was similar, being approximately three days after initiation of treatment. Comparable plasma artemisinin concentrations were observed between patients in both treatment groups at 1.5 and 3.0 h, although slightly higher levels were obtained with patients in the beta-cyclodextrin-artemisinin complex-treated group. The beta-cyclodextrin-artemisinin complex at a dose of 150 mg artemisinin was therapeutically equivalent to 250 mg Artemisinin 250. Additionally, patients receiving beta-cyclodextrin-artemisinin complex showed less variability in their plasma artemisinin concentrations at 1.5 h post-dosing, which suggested a more consistent rate of drug absorption.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  3. Susceptibility studies of Plasmodium falciparum isolates and clones against cycloguanil and pyrimethamine using the modified in vitro microtechnique
    Ang HH, Chan KL, Mak JW
    J Parasitol, 1996 Dec;82(6):1029-31.
    PMID: 8973418
    Six clones were derived from each Malaysian Plasmodium falciparum isolate and characterized for their susceptibilities against type II antifolate drugs, cycloguanil and pyrimethamine. Results showed that these isolates were of a heterogeneous population, with average IC50 values of Gombak C clones at 0.012-0.084 microM and 0.027-0.066 microM, ST 9 clones at 0.019-0.258 microM and 0.027-0.241 microM, ST 12 clones at 0.015-0.342 microM and 0.012-0.107 microM, ST 85 clones at 0.022-0.087 microM and 0.024-0.426 microM, and ST 148 clones at 0.027-0312 microM and 0.029-0.690 microM against cycloguanil and pyrimethamine, respectively. Generally, most of these clones displayed susceptibility patterns similar to their parent isolates except ST 9/A4, ST 9/A7, ST 9/B5, ST 9/D9, ST 9/D10, ST 148/A4, ST 148/A5, ST 148/A7, ST 148/F7, ST 148/F8 clones, which were sensitive at 0.027 microM, 0.019 microM, 0.022 microM, 0.063 microM, 0.037 microM, 0.031 microM, 0.042, microM, 0.042 microM, 0.062 microM, and 0.027 microM, whereas, ST 12/D7 clone was resistant at 0.342 microM, against cycloguanil respectively. However, ST 9/A4, ST 9/D8, ST 12/D5, ST 85/A5, ST 85/B3, ST 85/B4, ST 85/D3, ST 85/D7, ST 148/A6, and ST 148/A7 clones were resistant to pyrimethamine at 0.158 microM, 0.241 microM, 0.107 microM, 0.223 microM, 0.393 microM, 0.402 microM, 0.426 microM, 0.115 microM, 0.690 microM, and 0.520 microM, respectively.
    Matched MeSH terms: Plasmodium falciparum/drug effects*
  4. Fragmented population structure of plasmodium falciparum in a region of declining endemicity
    Anthony TG, Conway DJ, Cox-Singh J, Matusop A, Ratnam S, Shamsul S, et al.
    J Infect Dis, 2005 May 1;191(9):1558-64.
    PMID: 15809916
    The population genetic structure of Plasmodium falciparum differs between endemic regions, but the characteristics of a population recently fragmented by effective malaria control have been unknown.
    Matched MeSH terms: Plasmodium falciparum/genetics*
  5. Fulltext A Basis for Rapid Clearance of Circulating Ring-Stage Malaria Parasites by the Spiroindolone KAE609
    Zhang R, Suwanarusk R, Malleret B, Cooke BM, Nosten F, Lau YL, et al.
    J Infect Dis, 2016 Jan 1;213(1):100-4.
    PMID: 26136472 DOI: 10.1093/infdis/jiv358
    Recent clinical trials revealed a surprisingly rapid clearance of red blood cells (RBCs) infected with malaria parasites by the spiroindolone KAE609. Here, we show that ring-stage parasite-infected RBCs exposed to KAE609 become spherical and rigid, probably through osmotic dysregulation consequent to the disruption of the parasite's sodium efflux pump (adenosine triphosphate 4). We also show that this peculiar drug effect is likely to cause accelerated splenic clearance of the rheologically impaired Plasmodium vivax- and Plasmodium falciparum-infected RBCs.
    Matched MeSH terms: Plasmodium falciparum/drug effects*; Plasmodium falciparum/genetics
  6. Fulltext Contribution of Plasmodium knowlesi to Multispecies Human Malaria Infections in North Sumatera, Indonesia
    Lubis IND, Wijaya H, Lubis M, Lubis CP, Divis PCS, Beshir KB, et al.
    J Infect Dis, 2017 Apr 01;215(7):1148-1155.
    PMID: 28201638 DOI: 10.1093/infdis/jix091
    Background: As Indonesia works toward the goal of malaria elimination, information is lacking on malaria epidemiology from some western provinces. As a basis for studies of antimalarial efficacy, we set out to survey parasite carriage in 3 communities in North Sumatera Province.

    Methods: A combination of active and passive detection of infection was carried out among communities in Batubara, Langkat, and South Nias regencies. Finger-prick blood samples from consenting individuals of all ages provided blood films for microscopic examination and blood spots on filter paper. Plasmodium species were identified using nested polymerase chain reaction (PCR) of ribosomal RNA genes and a novel assay that amplifies a conserved sequence specific for the sicavar gene family of Plasmodium knowlesi.

    Results: Of 3731 participants, 614 (16.5%) were positive for malaria parasites by microscopy. PCR detected parasite DNA in samples from 1169 individuals (31.3%). In total, 377 participants (11.8%) harbored P. knowlesi. Also present were Plasmodium vivax (14.3%), Plasmodium falciparum (10.5%) and Plasmodium malariae (3.4%).

    Conclusions: Amplification of sicavar is a specific and sensitive test for the presence of P. knowlesi DNA in humans. Subpatent and asymptomatic multispecies parasitemia is relatively common in North Sumatera, so PCR-based surveillance is required to support control and elimination activities.

    Matched MeSH terms: Plasmodium falciparum/genetics*
  7. Malaria--an overview
    Gilles HM
    J Infect, 1989 Jan;18(1):11-23.
    PMID: 2644358
    The epidemiology, clinical features, diagnosis, prognosis, management, chemotherapy and chemoprophylaxis of malaria are reviewed.
    Matched MeSH terms: Plasmodium falciparum/drug effects
  8. Knob-positive and knob-negative Plasmodium falciparum differ in expression of a strain-specific malarial antigen on the surface of infected erythrocytes
    Aley SB, Sherwood JA, Howard RJ
    J. Exp. Med., 1984 Nov 01;160(5):1585-90.
    PMID: 6208311
    We have investigated the expression of a strain-specific malarial antigen on the surface of erythrocytes infected with knobless (K-) variants of knob-positive (K+) strains of Plasmodium falciparum. Aotus blood infected with K+ or K- parasites derived from two independent geographical isolates (Malayan camp and Santa Lucia) was surface iodinated by the lactoperoxidase method. Infected and uninfected erythrocytes were then separated by a new procedure involving equilibrium density sedimentation on a Percoll gradient containing sorbitol. Strain-specific antigens were readily identified on the surface of erythrocytes infected with either of the K+ strains by their characteristic size and detergent solubility. These proteins were not detected on the surface of erythrocytes infected with either of the K- variants nor on uninfected erythrocytes isolated from K+- or K- -infected blood. These results are consistent with a role for the strain-specific surface antigen in cytoadherence of P. falciparum-infected erythrocytes. Our findings represent the second biochemical difference (with the knob-associated histidine-rich protein) between K+ and K- P. falciparum.
    Matched MeSH terms: Plasmodium falciparum/classification; Plasmodium falciparum/immunology*
  9. EXPERIMENTAL INOCULATION OF MALARIA BY MEANS OF ANOPHELES LUDLOWI
    Darling ST
    J. Exp. Med., 1920 Aug 31;32(3):313-29.
    PMID: 19868447
    Three persons were experimentally inoculated with malaria by means of Anopheles ludlowi reared from larvae and infected with a pure strain of subtertian plasmodium (Plasmodium falciparum), thus proving that there exists no mechanical impediment or obstacle to the free exit of sporozoites from the salivary ducts or proboscis. In the dissection of infected mosquitoes there were no evidences of degenerated zygotes. Sporozoites appeared promptly in the salivary glands (9 to 12 days). Inoculation occurred with ease either in an interrupted feeding or after mosquitoes had been fed twice previously. The period of incubation was 14 and 18 days. The clinical manifestations were more severe in the subject that had never been infected with malaria previously, while the splenic enlargement was most pronounced in the subject infected after a long interval of freedom from malaria. In a third subject already suffering from tertian malaria there was only the slightest evidence of physical illness elicited by the superimposed subtertian infection; his temperature, however, became duly elevated. The type of febrile reaction in the two uncomplicated cases was at first tertian, becoming quotidian later, and this phenomenon in a pure strain leads strongly to the supposition that Plasmodium falciparum possesses inherently both tertian (or subtertian) and quotidian tendencies, as well as its well known tendencies to cause fever of the irregularly remittent or continued type. The creation of a specific plasmodium to account for clinical forms of aestivo-autumnal or subtertian malaria having a quotidian periodidty is probably unwarranted. In consideration of the facility with which this species can be infected and man inoculated experimentally, the occurrence of naturally infected wild specimens, and the positive epidemiological evidence, there should no longer exist in the minds of sanitarians any doubt as to its being a malarial carrier. Operations against this species can therefore be recommended without reservation and should be carried out without delay.
    Matched MeSH terms: Plasmodium falciparum
  10. Opantimycin A, a new metabolite isolated from Streptomyces sp. RK88-1355
    Nogawa T, Okano A, Lim CL, Futamura Y, Shimizu T, Takahashi S, et al.
    J Antibiot (Tokyo), 2017 02;70(2):222-225.
    PMID: 27599762 DOI: 10.1038/ja.2016.113
    Matched MeSH terms: Plasmodium falciparum/drug effects
  11. Mature Erythrocyte Surface Antigen Protein Identified in the Serum of Plasmodium falciparum-Infected Patients
    Zainudin NS, Othman N, Muhi J, Abdu Sani AA, Noordin R
    Am J Trop Med Hyg, 2015 Dec;93(6):1268-73.
    PMID: 26392156 DOI: 10.4269/ajtmh.15-0333
    This study was performed to identify circulating Plasmodium falciparum proteins in patient serum, which may be useful as diagnostic markers. Depletion of highly abundant proteins from each pooled serum sample obtained from P. falciparum-infected patients and healthy individuals was performed using the Proteoseek Antibody-Based Albumin/IgG Removal Kit (Thermo Scientific, Rockford, IL). In analysis 1, the depleted serum was analyzed directly by NanoLC-MS/MS. In analysis 2, the depleted serum was separated by two-dimensional electrophoresis followed by western blot analysis. Subsequently, the selected band was analyzed by NanoLC-MS/MS. The result of analysis 1 revealed the presence of two mature erythrocyte surface antigen (MESA) proteins and chloroquine resistance transporter protein (PfCRT). In addition, analysis 2 revealed an antigenic 75-kDa band when the membrane was probed with purified IgG from the pooled serum obtained from P. falciparum-infected patients. MS/MS analysis of this protein band revealed fragments of P. falciparum MESA proteins. Thus, in this study, two different analyses revealed the presence of Plasmodium MESA protein in pooled serum from malaria patients; thus, this protein should be further investigated to determine its usefulness as a diagnostic marker.
    Matched MeSH terms: Plasmodium falciparum/immunology*
  12. A genus- and species-specific nested polymerase chain reaction malaria detection assay for epidemiologic studies
    Singh B, Bobogare A, Cox-Singh J, Snounou G, Abdullah MS, Rahman HA
    Am J Trop Med Hyg, 1999 Apr;60(4):687-92.
    PMID: 10348249
    A nested polymerase chain reaction (PCR) assay that uses Plasmodium genus-specific primers for the initial PCR (nest 1) amplification and either genus- or species-specific primers for the nest 2 amplifications was tested on laboratory and field samples. With in vitro cultured Plasmodium falciparum-infected blood samples, it was capable of detecting six parasites/microl of blood using DNA prepared from 25-microl blood spots on filter paper. The assay was evaluated on fingerprick blood samples collected on filter paper from 129 individuals living in a malaria-endemic area in Malaysia. Malaria prevalence by genus-specific nested PCR was 35.6% (46 of 129) compared with 28.7% (37 of 129) by microscopy. The nested PCR detected seven more malaria samples than microscopy in the first round of microscopic examination, malaria in three microscopically negative samples, six double infections identified as single infections by microscopy and one triple infection identified as a double infection by microscopy. The nested PCR assay described is a sensitive technique for collecting accurate malaria epidemiologic data. When coupled with simple blood spot sampling, it is particularly useful for screening communities in remote regions of the world.
    Matched MeSH terms: Plasmodium falciparum/genetics*; Plasmodium falciparum/isolation & purification*
  13. Short report: differences in dihydrofolate reductase but not dihydropteroate synthase alleles in Plasmodium falciparum isolates from geographically distinct areas in Malaysia
    Cox-Singh J, Zakaria R, Abdullah MS, Rahman HA, Nagappan S, Singh B
    Am J Trop Med Hyg, 2001 6 27;64(1-2):28-31.
    PMID: 11425158
    Dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr) alleles were typed in 67 Malaysian Plasmodium falciparum isolates. The isolates were collected from two geographically distinct locations: 51 from Sabah, Malaysian Borneo, where sulfadoxine/pyrimethamine (SDX/PYR) is used to treat uncomplicated malaria and 16 from Peninsular Malaysia where in vivo resistance to SDX/PYR has been reported. A total of seven dhps alleles were identified with no significant difference in allele frequency between the 2 populations. Two of the dhps alleles described here have not been previously reported. Four dhfr alleles were detected in 67 P. falciparum isolates. Eighty-seven percent of the isolates from the Peninsula, where clinical SDX/PYR failure has been reported, had dhfr alleles with triple point mutations while all of the isolates from Sabah had dhfr alleles with 2 or less point mutations. The difference in dhfr allele frequency between the two populations was highly significant. There was no correlation between in vitro PYR response and accumulation of dhfr point mutations.
    Matched MeSH terms: Plasmodium falciparum/genetics*; Plasmodium falciparum/isolation & purification
  14. Short report: development of a new diagnostic method for Plasmodium falciparum infection using a reverse transcriptase-polymerase chain reaction
    Abdullah NR, Furuta T, Taib R, Kita K, Kojima S, Wah MJ
    Am J Trop Med Hyg, 1996 Feb;54(2):162-3.
    PMID: 8619441
    We describe here a reverse transcriptase-polymerase chain reaction method for the detection of malaria parasites. Ten in vitro-cultured isolates of Plasmodium falciparum and 16 specimens from patients infected with P. falciparum were used to examine the specificity and sensitivity of the test. The sensitivity of the test was 0.3 parasites per microliter of blood. Specificity was determined by matching the sequences of the specimens' DNA to published sequences of 18S ribosomal RNA genes in the species-specific region. The test proved to be very sensitive and specific for the detection of P. falciparum infection.
    Matched MeSH terms: Plasmodium falciparum/isolation & purification
  15. The ELISA-U: an enzyme-linked immunosorbent assay using urease as the enzyme marker for rapid detection of Plasmodium falciparum antibody in human serum
    Lee M, Lambros C
    Am J Trop Med Hyg, 1988 Nov;39(5):421-6.
    PMID: 3057927
    A visual, enzyme-linked immunosorbent assay using urease (ELISA-U) as the enzyme marker was adapted for rapid detection of antibody against Plasmodium falciparum. Flat-bottom, 96-well microtiter plates were coated with P. falciparum soluble antigen obtained by saponin and NP-40 treatment of parasite cultures. Antibody was detected by successive incubations with test sera, urease-conjugated rabbit-human antibody, and urease substrate. Reactive sera developed a definite and easily visualized purple color. Sera from patients with single infections of P. vivax or P. ovale were unreactive. No cross-reactivity was noted with sera from patients with rheumatoid arthritis, filariasis, amebiasis, schistosomiasis, dengue, scrub typhus, leptospirosis, or toxoplasmosis. The procedure can be performed at room temperature and completed within 1 hr. The sensitivity of the assay is comparable to that of the indirect fluorescent antibody test at all but the lowest dilutions tested.
    Matched MeSH terms: Plasmodium falciparum/immunology*
  16. A sensitive malaria immunoperoxidase assay for the detection of Plasmodium falciparum antibody
    Lim TS
    Am J Trop Med Hyg, 1988 Mar;38(2):255-7.
    PMID: 3281491
    A new and rapid malaria immunoperoxidase assay using the enzyme horseradish peroxidase in place of fluorescein isothiocyanate was developed to allow the serological measurement of antimalarial antibody by light microscopy. Acetone-fixed thin blood films prepared from cultured Plasmodium falciparum were used as the source of antigen. This malaria immunoperoxidase assay is as sensitive as, and occasionally more sensitive than, the indirect fluorescent antibody assay. It is easy to perform and the antigen used does not show cross-reactivity with sera from nonmalarial diseases.
    Matched MeSH terms: Plasmodium falciparum/immunology*
  17. Conserved and variant epitopes of target antigens of transmission-blocking antibodies among isolates of Plasmodium falciparum from Malaysia
    Foo A, Carter R, Lambros C, Graves P, Quakyi I, Targett GA, et al.
    Am J Trop Med Hyg, 1991 Jun;44(6):623-31.
    PMID: 1713424
    Monoclonal antibodies (MAbs) directed against different epitope regions on three sexual stage-specific gamete surface proteins of Plasmodium falciparum, Pfs 25, Pfs 230, and Pfs 48/45, were used to study the genetic diversity of these epitopes among fresh isolates of P. falciparum from Malaysia, using immunofluorescence microscopy (IFA). Among 45 Malaysian isolates, one epitope of Pfs 25, designated region I, showed evidence of variable reactivity with MAbs among different isolates; the Pfs 25 epitope, region II, was universally recognized by MAbs in all isolates. Two apparently distinct epitope regions of Pfs 230 were defined by MAbs, one of which was universally recognized by MAbs among the 45 isolates; the other was conserved in all but three isolates. The epitope regions of gamete-surface protein Pfs 48/45, designated regions I, IIa, IIb, IIc, III, and IV, were examined for reactivity by IFA in 33 isolates. Epitope regions I, IIb, III, and IV were conserved in all isolates; regions IIa and IIc existed in variant forms.
    Matched MeSH terms: Plasmodium falciparum/immunology*
  18. Interaction of Malaysian sera with Plasmodium vivax sporozoite antigen
    Lee M, Davis DR, Ballou WR, Folena-Wasserman G, Lewis GE
    Am J Trop Med Hyg, 1988 Dec;39(6):535-9.
    PMID: 3061309
    A seroepidemiologic survey of Plasmodium vivax and Plasmodium falciparum transmission was conducted in 94 Orang Asli children and adults. The prevalence of malaria was 46% in this population, and infections due to P. vivax and P. falciparum occurred with equal frequency. Multi-species infection was common, particularly in children less than 10 years of age. Circumsporozoite (CS) antibodies to P. vivax were detected by ELISA, using the recombinant protein NS181V20, in sera from 53-95% of all subjects in this study. The specificity of reactivity to NS181V20 was confirmed by immunofluorescence using air-dried sporozoites. CS antibodies to P. falciparum were present in less than 50% of the population less than 30 years of age. These data support further testing of this protein as a candidate vivax vaccine.
    Matched MeSH terms: Plasmodium falciparum/immunology
  19. Use of avidin-biotin-glucose oxidase complex to detect antimalarial antibody in serum by light microscopy
    Lee M, Lambros C
    Am J Trop Med Hyg, 1988 Aug;39(2):145-9.
    PMID: 3044152
    An immunohistochemical assay was developed combining an avidin-biotin-glucose oxidase complex procedure (ABC-GO) with light microscopy to detect specific antibody against Plasmodium falciparum. Thin blood films were prepared from culture material of P. falciparum and fixed with acetone. Antibody was detected by successive incubations with test serum, biotinylated goat antihuman antibody, avidin-biotin-glucose oxidase complex, and glucose oxidase substrate. In the presence of reactive serum, a blue precipitate formed on the parasites and could be visually observed with a 40x objective. Sera from patients with single infections for P. vivax or P. ovale were unreactive. No cross-reactivity was observed with sera from patients with rheumatoid arthritis, filariasis, amebiasis, schistosomiasis, dengue, scrub typhus, leptospirosis, or toxoplasmosis. The sensitivity of ABC-GO is comparable to that of the indirect fluorescent antibody test.
    Matched MeSH terms: Plasmodium falciparum/immunology*
  20. A longitudinal study of malaria antibodies in a Malaysian population. I. Group responses
    Mathews HM, Dondero TJ
    Am J Trop Med Hyg, 1982 Jan;31(1):14-8.
    PMID: 7036766
    The indirect hemagglutination test was used to measure malaria antibody levels in residents of an endemic area of Malaysia. Blood specimens were collected at 4-week intervals for a year. Seropositivity rates increased with age and number of episodes of malaria in young children. Although antibody levels were variable, titers tended to rise with parasitemia and fall in the absence of detected parasites. In general, the serologic indices tended to reflect the parasitologic findings.
    Matched MeSH terms: Plasmodium falciparum/immunology*; Plasmodium falciparum/isolation & purification
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