Displaying publications 1 - 20 of 39 in total

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  1. Fulltext Seroprevalence of Toxoplasma gondii Infection in Refugee and Migrant Pregnant Women along the Thailand-Myanmar Border
    van Enter BJD, Lau YL, Ling CL, Watthanaworawit W, Sukthana Y, Lee WC, et al.
    Am J Trop Med Hyg, 2017 Jul;97(1):232-235.
    PMID: 28719309 DOI: 10.4269/ajtmh.16-0999
    Toxoplasma gondii primary infection in pregnancy is associated with poor obstetric outcomes. This study aimed to determine the seroprevalence of Toxoplasma infection in pregnant migrant and refugee women from Myanmar attending antenatal care in Thailand. A random selection of 199 residual blood samples from first antenatal screen in 2014-2015 was tested for Toxoplasma IgG and IgM antibodies. Seroprevalence of Toxoplasma infection was 31.7% (95% confidence interval = 25.6-38.4). Avidity testing in the three positive IgM cases indicated all were past infections. Multiparity (≥ 3 children) was significantly associated with higher Toxoplasma seropositivity rates. Seroprevalence of T. gondii infection in this pregnant population is similar to the only other report from Myanmar, where multiparity was also identified as a significant association. Toxoplasma infection is important in pregnant women. Nevertheless, in this marginalized population, this infection may be given less priority, due to resource constraints in providing the most basic components of safe motherhood programs.
  2. Fulltext Digital microscope-assisted photography improves the accuracy of mosquito wing measurement
    Zulzahrin Z, Wong ML, Naziri MRA, Lau YL, Vythilingam I, Lee WC
    Heliyon, 2024 Feb 15;10(3):e25207.
    PMID: 38322922 DOI: 10.1016/j.heliyon.2024.e25207
    Wing measurement is an important parameter in many entomological studies. However, the methods of measuring wings vary with studies, and a gold standard method was not available for this procedure. This in turn limits researchers from confidently comparing their research findings with published data collected by other means of measurement. This study investigated the interchangeability of three commonly available methods for wing measurement, namely the calliper method, stereomicroscope-assisted photography method, and digital microscope-assisted photography method, using the laboratory colony of Aedes aegypti. It was found that the calliper method and the photography-based methods yielded similar results, hence the good interchangeability of these methods. Nevertheless, the digital microscope-assisted photography method yielded more accurate measurements, due to the higher resolution of the captured photos, and minimal technical bias during the data collection, as compared to the calliper-based and stereomicroscope-assisted photography methods. This study served as a reference for researchers to select the most suitable measurement method in future studies.
  3. Fulltext Rheopathologic Consequence of Plasmodium vivax Rosette Formation
    Zhang R, Lee WC, Lau YL, Albrecht L, Lopes SC, Costa FT, et al.
    PLoS Negl Trop Dis, 2016 08;10(8):e0004912.
    PMID: 27509168 DOI: 10.1371/journal.pntd.0004912
    Malaria parasites dramatically alter the rheological properties of infected red blood cells. In the case of Plasmodium vivax, the parasite rapidly decreases the shear elastic modulus of the invaded RBC, enabling it to avoid splenic clearance. This study highlights correlation between rosette formation and altered membrane deformability of P. vivax-infected erythrocytes, where the rosette-forming infected erythrocytes are significantly more rigid than their non-rosetting counterparts. The adhesion of normocytes to the PvIRBC is strong (mean binding force of 440pN) resulting in stable rosette formation even under high physiological shear flow stress. Rosetting may contribute to the sequestration of PvIRBC schizonts in the host microvasculature or spleen.
  4. Fulltext Moxifloxacin-warfarin interaction
    Yew KL, Lee WC
    Med J Malaysia, 2012 Aug;67(4):420-1.
    PMID: 23082454 MyJurnal
  5. Dataset describing problem factors of partnering relationships in the Malaysian construction industry
    Yao E, Lim YM, Leong CM, Lee WC, Pek CK
    Data Brief, 2022 Dec;45:108733.
    PMID: 36426078 DOI: 10.1016/j.dib.2022.108733
    The dataset indicates the problem factors which may influence the development of partnering relationship between two key project parties - the main contractor and the subcontractor. A total of 53 problem factors were identified and were clustered into five categories. An online questionnaire was used to elicit the viewpoints of these key parties with regards to the extent to which the factors have an impact on the partnering relationship in the Malaysian construction industry. The target respondents were managers and engineers of various construction companies in Malaysia with the main contractors or subcontractors who have projects in Kuala Lumpur, Shanghai and New Delhi. Both descriptive and quantitative analysis approaches were used to present the data. Relative Importance Index method was used to determine the top challenges to building favourable partnering relationships; and Partial Least Squares Structural-Equation Modelling (PLS-SEM) analysis was conducted to examine the role played by each cluster of factors in explaining the quality of partnering relationship between the main contractors and subcontractors. This data set would assist practitioners to work on the major problem factors to improve the quality of partnering relationship between the key participants in their present and future construction projects. By eliminating or minimizing these problem factors, practitioners will contribute significantly to effective supply chain management in the construction industry. The data would be of value to academics and industry professionals involved in the construction business domestically and internationally.
  6. Fulltext Perspectives of vector management in the control and elimination of vector-borne zoonoses
    Wong ML, Zulzahrin Z, Vythilingam I, Lau YL, Sam IC, Fong MY, et al.
    Front Microbiol, 2023;14:1135977.
    PMID: 37025644 DOI: 10.3389/fmicb.2023.1135977
    The complex transmission profiles of vector-borne zoonoses (VZB) and vector-borne infections with animal reservoirs (VBIAR) complicate efforts to break the transmission circuit of these infections. To control and eliminate VZB and VBIAR, insecticide application may not be conducted easily in all circumstances, particularly for infections with sylvatic transmission cycle. As a result, alternative approaches have been considered in the vector management against these infections. In this review, we highlighted differences among the environmental, chemical, and biological control approaches in vector management, from the perspectives of VZB and VBIAR. Concerns and knowledge gaps pertaining to the available control approaches were discussed to better understand the prospects of integrating these vector control approaches to synergistically break the transmission of VZB and VBIAR in humans, in line with the integrated vector management (IVM) developed by the World Health Organization (WHO) since 2004.
  7. Fulltext Functional and molecular surveillance of Helicobacter pylori antibiotic resistance in Kuala Lumpur
    Teh X, Khosravi Y, Lee WC, Leow AH, Loke MF, Vadivelu J, et al.
    PLoS One, 2014;9(7):e101481.
    PMID: 25003707 DOI: 10.1371/journal.pone.0101481
    Helicobacter pylori is the etiological agent for diseases ranging from chronic gastritis and peptic ulcer disease to gastric adenocarcinoma and primary gastric B-cell lymphoma. Emergence of resistance to antibiotics possesses a challenge to the effort to eradicate H. pylori using conventional antibiotic-based therapies. The molecular mechanisms that contribute to the resistance of these strains have yet to be identified and are important for understanding the evolutional pattern and selective pressure imposed by the environment.
  8. Functional and immunological mapping of domains of the reticulocyte binding protein, Plasmodium vivax PvRBP2a
    Tay MZ, Tang W, Lee WC, Ong ASM, Novera W, Malleret B, et al.
    J Infect Dis, 2024 Mar 05.
    PMID: 38441336 DOI: 10.1093/infdis/jiae111
    We previously described a novel Plasmodium vivax invasion mechanism into human reticulocytes via the PvRBP2a-CD98 receptor-ligand pair. We assessed the PvRBP2a epitopes involved in CD98 binding and recognised by antibodies from infected patients using linear epitope mapping. We identified two epitope clusters mediating PvRBP2a-CD98 interaction. One cluster named cluster B (PvRBP2a431-448, TAALKEKGKLLANLYNKL) was the target of antibody responses in P. vivax-infected humans. Peptides from each cluster were able to prevent live parasite invasion of human reticulocytes. These results provide new insights for development of a malaria blood stage vaccine against P. vivax.
  9. Fulltext Phylogenetic study of six species of Anopheles mosquitoes in Peninsular Malaysia based on inter-transcribed spacer region 2 (ITS2) of ribosomal DNA
    Sum JS, Lee WC, Amir A, Braima KA, Jeffery J, Abdul-Aziz NM, et al.
    Parasit Vectors, 2014;7:309.
    PMID: 24993022 DOI: 10.1186/1756-3305-7-309
    Molecular techniques are invaluable for investigation on the biodiversity of Anopheles mosquitoes. This study aimed at investigating the spatial-genetic variations among Anopheles mosquitoes from different areas of Peninsular Malaysia, as well as deciphering evolutionary relationships of the local Anopheles mosquitoes with the mosquitoes from neighbouring countries using the anopheline ITS2 rDNA gene.
  10. Deep-vein thrombosis rates after major orthopedic surgery in Asia. An epidemiological study based on postoperative screening with centrally adjudicated bilateral venography
    Piovella F, Wang CJ, Lu H, Lee K, Lee LH, Lee WC, et al.
    J Thromb Haemost, 2005 Dec;3(12):2664-70.
    PMID: 16359505
    BACKGROUND: The incidence of postsurgical venous thromboembolism is thought to be low in Asian ethnic populations.

    OBJECTIVE: We studied the incidence of deep-vein thrombosis (DVT) in Asian patients undergoing major orthopedic surgery of the lower limbs.

    PATIENTS/METHODS: We performed a prospective epidemiological study in 19 centers across Asia (China, Indonesia, South Korea, Malaysia, Philippines, Taiwan, and Thailand) in patients undergoing elective total hip replacement (THR), total knee replacement (TKR) or hip fracture surgery (HFS) without pharmacological thromboprophylaxis. The primary endpoint was the rate of DVT of the lower limbs documented objectively with bilateral ascending venography performed 6-10 days after surgery using a standardized technique and evaluated by a central adjudication committee unaware of local interpretation.

    RESULTS: Overall, of 837 Asian patients screened for this survey, 407 (48.6%, aged 20-99 years) undergoing THR (n = 175), TKR (n = 136) or HFS (n = 96) were recruited in 19 centers. DVT was diagnosed in 121 of 295 evaluable patients [41.0%, (95% confidence interval (CI): 35.4-46.7)]. Proximal DVT was found in 30 patients [10.2% (7.0-14.2)]. Total DVT and proximal DVT rates were highest in TKR patients (58.1% and 17.1%, respectively), followed by HFS patients (42.0% and 7.2%, respectively), then THR patients (25.6% and 5.8%, respectively). DVT was more frequent in female patients aged at least 65 years. Pulmonary embolism was clinically suspected in 10 of 407 patients (2.5%) and objectively confirmed in two (0.5%).

    CONCLUSIONS: The rate of venographic thrombosis in the absence of thromboprophylaxis after major joint surgery in Asian patients is similar to that previously reported in patients in Western countries.

  11. Fulltext The Impact of Geographical Variation in Plasmodium knowlesi Apical Membrane Protein 1 (PkAMA-1) on Invasion Dynamics of P. knowlesi
    Ng YL, Lee WC, Lau YL, Fong MY
    Trop Med Infect Dis, 2023 Jan 10;8(1).
    PMID: 36668963 DOI: 10.3390/tropicalmed8010056
    Plasmodium knowlesi has emerged as an important zoonotic parasite that causes persistent symptomatic malaria in humans. The signs and symptoms of malaria are attributed to the blood stages of the parasites, which start from the invasion of erythrocytes by the blood stage merozoites. The apical membrane protein 1 (AMA-1) plays an important role in the invasion. In this study, we constructed and expressed recombinant PkAMA-1 domain II (PkAMA-1-DII) representing the predominant haplotypes from Peninsular Malaysia and Malaysian Borneo and raised specific antibodies against the recombinant proteins in rabbits. Despite the minor amino acid sequence variation, antibodies raised against haplotypes from Peninsular Malaysia and Malaysian Borneo demonstrated different invasion inhibition (46.81% and 39.45%, respectively) to P. knowlesi A1-H.1, a reference strain derived from Peninsular Malaysia. Here, we demonstrated how a minor variation in a conserved parasite protein could cast a significant impact on parasite invasion biology, suggesting a complex host-switching of P. knowlesi from different locations. This may challenge the implementation of a standardized One Health approach against the transmission of knowlesi malaria.
  12. Extended field radiotherapy with or without chemotherapy in patients with cervical cancer and positive para-aortic lymph nodes: a single institution retrospective review
    Ng BH, Rozita A, Adlinda A, Lee WC, Wan Zamaniah W
    Asian Pac J Cancer Prev, 2015;16(9):3827-33.
    PMID: 25987044
    BACKGROUND: Positive para-aortic lymph node (PALN) at diagnosis in cervical cancer patients confers an unfavorable prognosis. This study reviewed the outcomes of extended field radiotherapy (EFRT) and concurrent chemotherapy with extended field RT (CCEFRT) in patients with positive PALN at diagnosis.

    MATERIALS AND METHODS: Medical records of 407 cervical cancer patients between 1st January 2002 to 31st December 2012 were reviewed. Some 32 cases with positive PALN were identified to have received definitive extended field radiotherapy with or without chemotherapy. Treatment outcomes, clinicopathological factors affecting survival and radiotherapy related acute and late effects were analyzed.

    RESULTS: Totals of 13 and 19 patients underwent EFRT and CCEFRT respectively during the period of review. The median follow-up was 70 months. The 5-year overall survival (OS) was 40% for patients who underwent CCEFRT as compared to 18% for patients who had EFRT alone, with median survival sof 29 months and 13 months, respectively. The 5-years progression free survival (PFS) for patients who underwent CCEFRT was 32% and 18% for those who had EFRT. Median PFS were 18 months and 12 months, respectively. Overall treatment time (OTT) less than 8 weeks reduced risk of death by 81% (HR=0.19). Acute side effects were documented in 69.7% and 89.5% of patients who underwent EFRT and CCEFRT, respectively. Four patients (12.5%) developed radiotherapy late toxicity and there was no treatment-related death observed.

    CONCLUSIONS: CCEFRT is associated with higher 5-years OS and median OS compared to EFRT and with tolerable level of acute and late toxicities in selected patients with cervical cancer and PALN metastasis.

  13. Fulltext Preoperative long course chemoirradiation in a developing country for rectal carcinoma: Kuala Lumpur hospital experience
    Lee WC, Yusof MM, Lau FN, Phua VC
    Asian Pac J Cancer Prev, 2013;14(6):3941-4.
    PMID: 23886211
    BACKGROUND: The use of preoperative chemoirradiation is the commonest treatment strategy employed in Malaysia for locally advanced rectal cancer. We need to determine the local control and survival rates for comparison with established rates in the literature.

    MATERIALS AND METHODS: This retrospective study analyzed all newly diagnosed patients with rectal adenocarcinoma who underwent long course preoperative radiotherapy (RT) at the Department of Radiotherapy and Oncology, Kuala Lumpur Hospital (HKL) between 1st January 2004 and 31st December 2010. The aim of the study was to determine the radiological response post radiotherapy, pathological response including circumferential resection margin (CRM) status, 3 years local control, 3 years overall survival (OS) and 3 years disease free survival (DFS). Statistical analysis was performed using the SPSS software. Kaplan-Meier and log rank analysis were used to determine survival outcomes.

    RESULTS: A total of 507 patients with rectal cancer underwent RT at HKL. Sixty seven who underwent long course preoperative RT were eligible for this study. The median age at diagnosis was 60 years old with a range of 26-78 years. The median tumour location was 6 cm from the anal verge. Most patients had suspicion of mesorectum involvement (95.5%) while 28.4% of patients had enlarged pelvic nodes on staging CT scan. All patients underwent preoperative chemo-irradiation except for five who had preoperative RT alone. Only 38 patients underwent definitive surgery (56.7%). Five patients were deemed to be inoperable radiologically and 3 patients were found to have unresectable disease intraoperatively. The remaining 21 patients defaulted surgery (31.3%). The median time from completion of RT to surgery was 8 weeks (range 5.6 to 29.4 weeks). Fifteen patients (39.5%) had surgery more than 8 weeks after completion of RT. Complete pathological response was noted in 4 patients (10.5%). The pathological CRM positive rate after RT was 18.4%. With a median follow-up of 38.8 months, the 3 year local control rate was 67%. The 3 years rate for CRM positive (<2 mm), CRM clear (>2 mm) and pCR groups were 0%, 88.1% and 100% respectively (p-value of 0.007). The 3 year OS and DFS were 57.3% and 44.8% respectively.

    CONCLUSIONS: In conclusion, the approach of long course preoperative chemoirradiation for rectal cancer needs to be re-examined in our local setting. The high rate of local recurrence is worrying and is mainly due to patient defaulting post-preoperative chemoirradiation or delayed definitive surgery.
  14. Fulltext Hyperparasitaemic human Plasmodium knowlesi infection with atypical morphology in peninsular Malaysia
    Lee WC, Chin PW, Lau YL, Chin LC, Fong MY, Yap CJ, et al.
    Malar J, 2013;12:88.
    PMID: 23496970 DOI: 10.1186/1475-2875-12-88
    Plasmodium knowlesi is a potentially life-threatening zoonotic malaria parasite due to its relatively short erythrocytic cycle. Microscopic identification of P. knowlesi is difficult, with "compacted parasite cytoplasm" being one of the important identifying keys. This report is about a case of hyperparasitaemic human P. knowlesi infection (27% parasitaemia) with atypical amoeboid morphology. A peninsular Malaysian was admitted to the hospital with malaria. He suffered anaemia and acute kidney function impairment. Microscopic examination, assisted by nested PCR and sequencing confirmed as P. knowlesi infection. With anti-malarial treatment and several medical interventions, patient survived and recovered. One-month medical follow-up was performed after recovery and no recrudescence was noted. This case report highlights the extreme hyperparasitaemic setting, the atypical morphology of P. knowlesi in the patient's erythrocytes, as well as the medical interventions involved in this successfully treated case.
  15. Statistical evaluation of alternative light sources for bloodstain photography
    Lee WC, Khoo BE, Bin Abdullah AF, Abdul Aziz ZB
    J Forensic Sci, 2013 May;58(3):658-63.
    PMID: 23488634 DOI: 10.1111/1556-4029.12103
    Bloodstain photography is important in forensic applications, especially for bloodstain pattern analysis. This study compares the enhancement effect of bloodstain photography using three different types of light source: fluorescent white light, near-ultraviolet (UV) light-emitting diode (LED) light, and 410 nm LED light. Randomized complete block designs were implemented to identify the lighting that would statistically produce the best enhancement results for bloodstains on different types of surfaces. Bloodstain samples were prepared on white cotton, brown carpet, tar road, and wood. These samples were photographed in darkroom conditions using a Canon EOS 50D digital SLR camera, with Canon EFS 60 mm f/2.8 Macro USM lens. Two-way analysis of variance and Fisher's least significant difference test were used to analyze the contrast of the images. The statistical analysis showed that 410 nm light is the best among the tested lights for enhancing bloodstains on the tested surfaces, where the contrast of bloodstain to background was the highest.
  16. Enhancement of seminal stains using background correction algorithm with colour filters
    Lee WC, Khoo BE, Abdullah AFL
    Forensic Sci Int, 2016 06;263:1-9.
    PMID: 27061146 DOI: 10.1016/j.forsciint.2016.03.046
    Evidence in crime scenes available in the form of biological stains which cannot be visualized during naked eye examination can be detected by imaging their fluorescence using a combination of excitation lights and suitable filters. These combinations selectively allow the passage of fluorescence light emitted from the targeted stains. However, interference from the fluorescence generated by many of the surface materials bearing the stains often renders it difficult to visualize the stains during forensic photography. This report describes the use of background correction algorithm (BCA) to enhance the visibility of seminal stain, a biological evidence that fluoresces. While earlier reports described the use of narrow band-pass filters for other fluorescing evidences, here, we utilize BCA to enhance images captured using commonly available colour filters, yellow, orange and red. Mean-based contrast adjustment was incorporated into BCA to adjust the background brightness for achieving similarity of images' background appearance, a crucial step for ensuring success while implementing BCA. Experiment results demonstrated the effectiveness of our proposed colour filters' approach using the improved BCA in enhancing the visibility of seminal stains in varying dilutions on selected surfaces.
  17. Fulltext Elucidation of the Metabolic Network of Helicobacter pylori J99 and Malaysian Clinical Strains by Phenotype Microarray
    Lee WC, Goh KL, Loke MF, Vadivelu J
    Helicobacter, 2017 Feb;22(1).
    PMID: 27258354 DOI: 10.1111/hel.12321
    Helicobacter pylori colonizes almost half of the human population worldwide. H. pylori strains are genetically diverse, and the specific genotypes are associated with various clinical manifestations including gastric adenocarcinoma, peptic ulcer disease (PUD), and nonulcer dyspepsia (NUD). However, our current knowledge of the H. pylori metabolism is limited. To understand the metabolic differences among H. pylori strains, we investigated four Malaysian H. pylori clinical strains, which had been previously sequenced, and a standard strain, H. pylori J99, at the phenotypic level.
  18. Fulltext The complete methylome of Helicobacter pylori UM032
    Lee WC, Anton BP, Wang S, Baybayan P, Singh S, Ashby M, et al.
    BMC Genomics, 2015;16:424.
    PMID: 26031894 DOI: 10.1186/s12864-015-1585-2
    The genome of the human gastric pathogen Helicobacter pylori encodes a large number of DNA methyltransferases (MTases), some of which are shared among many strains, and others of which are unique to a given strain. The MTases have potential roles in the survival of the bacterium. In this study, we sequenced a Malaysian H. pylori clinical strain, designated UM032, by using a combination of PacBio Single Molecule, Real-Time (SMRT) and Illumina MiSeq next generation sequencing platforms, and used the SMRT data to characterize the set of methylated bases (the methylome).
  19. Fulltext Glycophorin C (CD236R) mediates vivax malaria parasite rosetting to normocytes
    Lee WC, Malleret B, Lau YL, Mauduit M, Fong MY, Cho JS, et al.
    Blood, 2014 May 01;123(18):e100-9.
    PMID: 24652986 DOI: 10.1182/blood-2013-12-541698
    Rosetting phenomenon has been linked to malaria pathogenesis. Although rosetting occurs in all causes of human malaria, most data on this subject has been derived from Plasmodium falciparum. Here, we investigate the function and factors affecting rosette formation in Plasmodium vivax. To achieve this, we used a range of novel ex vivo protocols to study fresh and cryopreserved P vivax (n = 135) and P falciparum (n = 77) isolates from Thailand. Rosetting is more common in vivax than falciparum malaria, both in terms of incidence in patient samples and percentage of infected erythrocytes forming rosettes. Rosetting to P vivax asexual and sexual stages was evident 20 hours postreticulocyte invasion, reaching a plateau after 30 hours. Host ABO blood group, reticulocyte count, and parasitemia were not correlated with P vivax rosetting. Importantly, mature erythrocytes (normocytes), rather than reticulocytes, preferentially form rosetting complexes, indicating that this process is unlikely to directly facilitate merozoite invasion. Although antibodies against host erythrocyte receptors CD235a and CD35 had no effect, Ag-binding fragment against the BRIC 4 region of CD236R significantly inhibited rosette formation. Rosetting assays using CD236R knockdown normocytes derived from hematopoietic stem cells further supports the role of glycophorin C as a receptor in P vivax rosette formation.
  20. Fulltext Giemsa-stained wet mount based method for reticulocyte quantification: a viable alternative in resource limited or malaria endemic settings
    Lee WC, Russell B, Lau YL, Fong MY, Chu C, Sriprawat K, et al.
    PLoS One, 2013;8(4):e60303.
    PMID: 23565221 DOI: 10.1371/journal.pone.0060303
    The quantity of circulating reticulocytes is an important indicator of erythropoietic activity in response to a wide range of haematological pathologies. While most modern laboratories use flow cytometry to quantify reticulocytes, most field laboratories still rely on 'subvital' staining. The specialist 'subvital' stains, New Methylene Blue (NMB) and Brilliant Crésyl Blue are often difficult to procure, toxic, and show inconsistencies between batches. Here we demonstrate the utility of Giemsa's stain (commonly used microbiology and parasitology) in a 'subvital' manner to provide an accurate method to visualize and count reticulocytes in blood samples from normal and malaria-infected individuals.
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