Displaying publications 1 - 20 of 220 in total

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  1. 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.
  2. Lau YL, Ismail IB, Izati Binti Mustapa N, Lai MY, Tuan Soh TS, Hassan AH, et al.
    Am J Trop Med Hyg, 2020 Dec;103(6):2350-2352.
    PMID: 33098286 DOI: 10.4269/ajtmh.20-1079
    A simple and rapid reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the detection of SARS-CoV-2. The RT-LAMP assay was highly specific for SARS-CoV-2 and was able to detect one copy of transcribed SARS-CoV-2 RNA within 24 minutes. Assay validation performed using 50 positive and 32 negative clinical samples showed 100% sensitivity and specificity. The RT-LAMP would be valuable for clinical diagnosis and epidemiological surveillance of SARS-CoV-2 infection in resource-limited areas as it does not require the use of sophisticated and costly equipment.
  3. Liew PS, Teh CS, Lau YL, Thong KL
    Trop Biomed, 2014 Dec;31(4):709-20.
    PMID: 25776596 MyJurnal
    Shigellosis is a foodborne illness caused by the genus Shigella and is an important global health issue. The development of effective techniques for rapid detection of this pathogen is essential for breaking the chain of transmission. Therefore, we have developed a novel loop-mediated isothermal amplification (LAMP) assay targeting the invasion plasmid antigen H (ipaH) gene to rapidly detect Shigella species. This assay could be performed in 90 min at an optimal temperature of 64ºC, with endpoint results visualized directly. Notably, the method was found to be more sensitive than conventional PCR. Indeed, the detection limit for the LAMP assay on pure bacterial cultures was 5.9 x 10(5) CFU/ml, while PCR displayed a limit of 5.9 x 10(7) CFU/ml. In spiked lettuce samples, the sensitivity of the LAMP assay was 3.6 x 10(4) CFU/g, whereas PCR was 3.6 x 10(5) CFU/g. Overall, the assay accurately identified 32 Shigella spp. with one enteroinvasive Escherichia coli displaying positive reaction while the remaining 32 non-Shigella strains tested were negative.
  4. Elyana FN, Al-Mekhlafi HM, Ithoi I, Abdulsalam AM, Dawaki S, Nasr NA, et al.
    Parasit Vectors, 2016 07 16;9(1):398.
    PMID: 27422533 DOI: 10.1186/s13071-016-1678-z
    BACKGROUND: Intestinal parasitic infections (IPIs) are still major health problems in many developing countries including Malaysia, particularly in the poor and socioeconomically deprived rural and remote communities in Peninsular Malaysia. This study was conducted to determine the prevalence of IPIs and to identify the key factors associated with intestinal polyparasitism as well as to evaluate the knowledge, attitude and practices (KAP) on IPIs among rural Orang Asli and Malay communities in Terengganu, Malaysia.

    METHODS: A cross-sectional study was conducted among 340 participants (165 Orang Asli and 175 Malay) aged ≤ 15 years from the Hulu Terengganu and Kemaman districts of Terengganu. Faecal samples were examined for the presence of intestinal parasites by using direct smear, formalin-ether sedimentation, trichrome stain, modified Ziehl Neelsen stain, in vitro cultivation in Jones' medium, Kato Katz and Harada Mori techniques. Demographic, socioeconomic, environmental and behavioural information of the participants and their KAP for IPIs were collected by using a pre-tested questionnaire.

    RESULTS: Overall, 149 (90.3 %) Orang Asli and 43 (24.6 %) Malay children were infected by at least one parasite species. The overall prevalences of intestinal polyparasitism among the Orang Asli and Malay were 68.5 % (113/165) and 14.3 % (25/175), respectively. Multiple logistic regression analysis showed that using unsafe water supply as a source for drinking water, the presence of domestic animals, not wearing shoes when outside, not washing vegetables before consumption, not washing hands after playing with soil, indiscriminate defecation and the low level of mother's education were the key risk factors for intestinal polyparasitism among the Orang Asli, while working mothers and the presence of domestic animals were the risk factors among the Malay children. Almost all the Malays were well aware about the IPIs while Orang Asli respondents had a poor level of related awareness.

    CONCLUSIONS: This study demonstrates that IPIs are highly prevalent in rural Terengganu, Malaysia. Community awareness about IPIs was found to be imperative in protecting Malay children from these infections. An integrated control programme for the prevention and control of IPIs is highly recommended for these communities, with a special emphasis on the Orang Asli population.

  5. Lai MY, Ponnampalavanar SSS, Omar SFS, Lau YL
    Acta Trop, 2024 Mar;251:107120.
    PMID: 38199452 DOI: 10.1016/j.actatropica.2024.107120
    Combining the advantages of PCR and LAMP, we described a new technique, namely PCR-LAMP, for malaria diagnosis. The whole process of DNA amplification can be completed in 35 min. This hybrid amplification technique markedly improved the sensitivity of detection compared to the classic single PCR or LAMP assay alone. PCR-LAMP assay had a detection limit of 1 copy/µL for P. knowlesi and P. ovale, 0.1 copy/µL for P. vivax, P. falciparum and P. malariae, respectively. To facilitate the endpoint detection, xylenol orange was added. Positive samples were indicated in orange while negative reactions were violet. The inclusion of xylenol orange into the LAMP reaction mix significantly reduces the post-amplification workload. Without relying on the use of specific instruments, the color changes of the amplicons could be visualized directly through the naked eye. In conclusion, PCR-LAMP poses the potential to be developed as a new malaria molecular diagnosis tool.
  6. Syahmi AR, Vijayarathna S, Sasidharan S, Latha LY, Kwan YP, Lau YL, et al.
    Molecules, 2010 Nov;15(11):8111-21.
    PMID: 21072022 DOI: 10.3390/molecules15118111
    Elaeis guineensis (Arecaceae) is widely used in West African traditional medicine for treating various ailments. An evaluation on the toxicity of extracts of this plant is crucial to support the therapeutic claims. The acute oral toxicity and brine shrimp lethality of a methanolic extract of this plant was tested. Oral administration of crude extract at the highest dose of 5,000 mg/kg resulted in no mortalities or evidence of adverse effects, implying that E. guineensis is nontoxic. Normal behavioral pattern, clinical signs and histology of vital organs confirm this evidence. The E. guineensis extracts screened for toxicity against brine shrimp had 50% lethal concentration (LC₅₀) values of more than 1.0 mg/mL (9.00 and 3.87 mg/mL, at 6 and 24 h, respectively), confirming that the extract was not toxic. Maximum mortalities occurred at 100 mg/mL concentration while the least mortalities happened to be at 0.195 mg/mL concentration. The results of both tests confirm that E. guineensis is nontoxic and hence safe for commercial utilization.
  7. Jothy SL, Zakaria Z, Chen Y, Lau YL, Latha LY, Sasidharan S
    Molecules, 2011 Jun 23;16(6):5268-82.
    PMID: 21701437 DOI: 10.3390/molecules16065268
    BACKGROUND AND OBJECTIVE: Cassia fistula is widely used in traditional medicine to treat various types of ailments. The evaluation of toxic properties of C. fistula is crucial when considering public health protection because exposure to plant extracts can result in undesirable effects on consumers. Hence, in this study the acute oral toxicity of C. fistula seeds extract was investigated in mice.

    RESULTS: Oral administration of crude extract at the highest dose of 5000 mg/kg resulted in no mortalities or evidence of adverse effects, implying that C. fistula in nontoxic. Throughout 14 days of the treatment no changes in behavioural pattern, clinical sign and body weight of mice in both control and treatment groups. Also there were no any significant elevations observed in the biochemical analysis of the blood serum. Further, histopathological examination revealed normal architecture and no significant adverse effects observed on the kidney, heart, liver, lung and spleen.

    CONCLUSIONS: Overall, the results suggest that, the oral administration of C. fistula methanolic seeds extract did not produce any significant toxic effect in mice. Hence, the extract can be utilized for pharmaceutical formulations.

  8. Lau YL, Lee WC, Tan LH, Kamarulzaman A, Syed Omar SF, Fong MY, et al.
    Malar J, 2013;12:389.
    PMID: 24180319 DOI: 10.1186/1475-2875-12-389
    Plasmodium ovale is one of the causative agents of human malaria. Plasmodium ovale infection has long been thought to be non-fatal. Due to its lower morbidity, P. ovale receives little attention in malaria research.
  9. Leong CS, Vythilingam I, Wong ML, Wan Sulaiman WY, Lau YL
    Acta Trop, 2018 Sep;185:115-126.
    PMID: 29758171 DOI: 10.1016/j.actatropica.2018.05.008
    The resistance status of Selangor Aedes aegypti (Linnaeus) larvae against four major groups of insecticides (i.e., organochlorines, carbamates, organophosphates and pyrethroids) was investigated. Aedes aegypti were susceptible against temephos (organophosphate), although resistance (RR50 = 0.21-2.64) may be developing. The insecticides susceptibility status of Ae. aegypti larvae were found heterogeneous among the different study sites. Results showed that Ae. aegypti larvae from Klang, Sabak Bernam and Sepang were susceptible against all insecticides tested. However, other study sites exhibited low to high resistance against all pyrethroids (RR50 = 1.19-32.16). Overall, the application of synergists ethacrynic acid, S.S.S.- tributylphosphorotrithioate and piperonyl butoxide increased the toxicity of insecticides investigated. However, the application failed to increase the mortality to susceptible level (>97%) for certain populations, therefore there are chances of alteration of target site resistance involved. Biochemical assays revealed that α-esterase, (Gombak, Kuala Langat, Kuala Selangor and Sabak Bernam strains) β-esterase (Klang and Sabak Bernam strains), acetylcholinesterase (Kuala Selangor and Sabak Bernam strains), glutathione-S-transferase (Kuala Selangor and Sabak Bernam strains) and mono-oxygenases (Gombak, Hulu Langat, Hulu Selangor and Kuala Langat strains) were elevated. Spearman rank-order correlation indicated a significant correlation between resistance ratios of: DDT and deltamethrin (r = 0.683, P = 0.042), cyfluthrin and deltamethrin (r = 0.867, P =0.002), cyflyuthrin and lambdacyhalothrin (r = 0.800, P =0.010), cyfluthrin and permethrin (r = 0.770, P =0.015) deltamethrin and permethrin (r = 0.803, P =0.088), propoxur and malathion (r = 0.867, P = 0.002), malathion and temephos (r = 0.800, P = 0.010), etofenprox and MFO enzyme (r = 0.667, P =0.050). The current study provides baseline information for vector control programs conducted by local authorities. The susceptibility status of Ae. aegypti should be monitored sporadically to ensure the effectiveness of current vector control strategy in Selangor.
  10. Amir A, Ngui R, Ismail WH, Wong KT, Ong JS, Lim YA, et al.
    Am J Trop Med Hyg, 2016 Aug 03;95(2):410-2.
    PMID: 27325803 DOI: 10.4269/ajtmh.16-0007
    Human anisakiasis is a zoonosis acquired by eating raw or undercooked infected seafood. Herein, we report a case of acute dysentery caused by anisakiasis in a 64-year-old man in Malaysia. A colonoscopy was performed and a nematode larva was found penetrating the mucosa of the ascending colon. Bleeding was observed at the site of penetration. Y-shaped lateral epidermal cords were seen from the cross section of the worm, which is a prominent feature of Anisakis larva. Molecular analysis using polymerase chain reaction of cytochrome oxidase 2 (cox2) gene confirmed the specimen to be larva of Anisakis simplex.
  11. Muslim A, Fong MY, Mahmud R, Lau YL, Sivanandam S
    Parasit Vectors, 2013;6:219.
    PMID: 23898840 DOI: 10.1186/1756-3305-6-219
    In 2011, we reported occurrence of natural human infections with Brugia pahangi, a filarial worm of dogs and cats, in a surburb of Kuala Lumpur, the capital city of Malaysia. Our preliminary entomological survey at that time suggested the mosquito species Armigeres subalbatus as the vector of the zoonotic infections. In this present report, we provide biological evidence to confirm our preliminary finding.
  12. Liew J, Amir A, Chen Y, Fong MY, Razali R, Lau YL
    Clin Chim Acta, 2015 Aug 25;448:33-8.
    PMID: 26086445 DOI: 10.1016/j.cca.2015.06.006
    Autoantibodies or antibodies against self-antigens are produced either during physiological processes to maintain homeostasis or pathological process such as trauma and infection. Infection with parasites including Plasmodium has been shown to generally induce elevated self-antibody (autoantibody) levels. Plasmodium knowlesi is increasingly recognized as one of the most important emerging human malaria in Southeast Asia that can cause severe infection leading to mortality. Autoimmune-like phenomena have been hypothesized to play a role in the protective immune responses in malaria infection.
  13. Italiano CM, Wong KT, AbuBakar S, Lau YL, Ramli N, Syed Omar SF, et al.
    Clin Infect Dis, 2015 Apr 1;60(7):1134.
    PMID: 25537869 DOI: 10.1093/cid/ciu1163
  14. Jothy SL, Zakaria Z, Chen Y, Lau YL, Latha LY, Shin LN, et al.
    Molecules, 2011 Sep 05;16(9):7583-92.
    PMID: 21894090 DOI: 10.3390/molecules16097583
    BACKGROUND AND OBJECTIVE: Cassia fistula L belongs to the family Leguminosae, and it is one of the most popular herbal products in tropical countries. C. fistula seeds have been used as a herbal medicine and have pharmacological activity which includes anti-bacterial, anti-fungal, and antioxidant properties. The goal of this study was to identify compounds from C. fistula seeds which are responsible for anti-Candida albicans activity using bioassay-directed isolation.

    RESULTS: The preliminary phytochemical screening of the plant seed revealed the presence of anthraquinones, flavonoids, saponins, tannins and terpenoids. The isolation of active compounds was carried out in four steps: multiple extractions, fractionation using column chromatography and purification using preparative thin-layer chromatography (TLC) and liquid chromatography/mass spectrometry (LC/MS). The structure of separated compounds was determined on the basis of mass spectrometry data. One compound was identified is roseanone.

    CONCLUSIONS: The MS analysis on the active fraction from seed extract of C. fistula confirmed the presence of roseanone with antiyeast activity.

  15. Leung GK, Ying D, Mak CC, Chen XY, Xu W, Yeung KS, et al.
    Mol Genet Genomic Med, 2017 Jan;5(1):40-49.
    PMID: 28116329 DOI: 10.1002/mgg3.258
    Cystic fibrosis (CF) is a rare condition in Asians. Since 1985, only about 30 Chinese patients have been reported with molecular confirmation.
  16. Liew JWK, Ooi CH, Snounou G, Lau YL
    Am J Trop Med Hyg, 2019 12;101(6):1402-1404.
    PMID: 31595863 DOI: 10.4269/ajtmh.19-0305
    Here are two cases of recurring ovale malaria in Sarawak, Malaysia, that are likely relapses that occurred 1-2 months after successful treatment of the initial imported falciparum malaria with artemisinin-based combined therapy. The patients have no history or recollection of previous malaria episodes. These cases add to the limited evidence on the relapsing nature of Plasmodium ovale, after a febrile episode. In regions where P. ovale is not known to be autochthonous, active follow-up of treated imported malaria patients is highly recommended following their return, particularly to areas nearing or having achieved elimination.
  17. Mat Salleh NH, Rahman MFA, Samsusah S, De Silva JR, Ng DC, Ghozali AH, et al.
    Trans R Soc Trop Med Hyg, 2020 Sep 01;114(9):700-703.
    PMID: 32511702 DOI: 10.1093/trstmh/traa042
    Five children in Pos Lenjang, Pahang, Malaysia were PCR-positive for vivax malaria and were admitted to the hospital from 5 to 26 July 2019. One of the patients experienced three episodes of recurrence of vivax malaria. Microsatellite analysis showed that reinfection is unlikely. Drug resistance analysis indicated that Riamet (artemether-lumefantrine) is effective. Cytochrome P450 2D6 (CYP2D6) testing showed that this patient has defective CYP2D6 function. Primaquine failure to clear the Plasmodium vivax hypnozoites may be the cause of recurring infections in this patient. This report highlights the need for the development of liver-stage curative antimalarials that do not require metabolism by the CYP2D6 enzyme.
  18. Lau YL, Shamilah H, Fong MY
    Trop Biomed, 2006 Dec;23(2):186-93.
    PMID: 17322821 MyJurnal
    A truncated form of surface antigen 2 (SAG2) of the protozoan parasite Toxoplasma gondii was cloned and expressed in the methylotrophic yeast Pichia pastoris. This recombinant antigen, designated as recSAG2-N, contained only the N-terminal half of the native SAG2. The recSAG2-N was secreted by the Pichia pastoris into the culture supernatant, and it was harvested by using the trichloroacetic acid precipitation method. Specificity of recSAG2-N was evaluated in western blot assays. Fifty human serum samples, including 32 from confirmed cases of toxoplasmosis, were tested. Results from the assays showed that recSAG2-N reacted with sera from the toxoplasmosis cases only. In vivo experiments showed that serum from mice which received recSAG2-N reacted with the native SAG2 of T. gondii.
  19. Fong MY, Lau YL, Zulqarnain M
    Biotechnol Lett, 2008 Apr;30(4):611-8.
    PMID: 18043869
    The surface antigen 2 (SAG2) gene of the protozoan parasite, Toxoplasma gondii, was cloned and extracellularly expressed in the yeast Pichia pastoris. The effectiveness of the secreted recombinant SAG2 (rSAG2-S) as a serodiagnosis reagent was assessed by western blots and ELISA. In the western blot assay, rSAG2-S reacted with all Toxoplasma-antibody positive human serum samples but not with Toxoplasma-negative samples. In the ELISA, rSAG2-S yielded sensitivity rates ranging from 80% (IgG negative, IgM positive) to 100% (IgG positive, IgM negative). In vivo experiments showed that serum from mice immunized with rSAG2-S reacted specifically with the native SAG2 of T. gondii. These mice were protected when challenged with live cells of T. gondii.
  20. Lau YL, Hasan MT, Thiruvengadam G, Idris MM, Init I
    Trop Biomed, 2010 Dec;27(3):525-33.
    PMID: 21399595
    GRA4 of Toxoplasma gondii has been shown to prompt IgG, IgM and IgA responses in previous studies and is thus considered one of the major immunogenic proteins from T. gondii that can be used for both diagnostics purposes and vaccine development. This study seeks to clone and express the GRA4 in Pichia pastoris, which has numerous advantages over other systems for expression of eukaryotic proteins. In order to achieve this, the gene was cloned into the pPICZα A expression vector, which was then incorporated into the P. pastoris genome via insertional integration for expression of the recombinant protein, under the AOX1 promoter. The antigen was expressed along with the prepro sequence of the α-factor of yeast so that it could be excreted out of the P. pastoris cells and obtained from the medium. Upon SDS-PAGE analysis it was found that the recombinant protein was expressed optimally as a 40 kDa protein after 96 hours of induction with 0.75% of methanol. The expressed GRA4 protein showed discrepancy in size with the calculated molecular mass. This may be attributed to the various posttranslational modifications including glycosylation and phosphorylation. Despite the difference in molecular weight, the recombinant protein was able to detect toxoplasmosis in Western blot format. The recombinant GRA4 was expressed with an intact polyhistidine-tag, which could be used for future purification of the antigen.
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