Displaying publications 1 - 20 of 50 in total

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  1. 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.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  2. Kong BH, Hanifah YA, Yusof MY, Thong KL
    Trop Biomed, 2011 Dec;28(3):563-8.
    PMID: 22433885 MyJurnal
    Acinetobacter baumannii, genomic species 3 and 13TU are being increasingly reported as the most important Acinetobacter species that cause infections in hospitalized patients. These Acinetobacter species are grouped in the Acinetobacter calcoaceticus- Acinetobacter baumannii (Acb) complex. Differentiation of the species in the Acb-complex is limited by phenotypic methods. Therefore, in this study, amplified ribosomal DNA restriction analysis (ARDRA) was applied to confirm the identity A. baumannii strains as well as to differentiate between the subspecies. One hundred and eighty-five strains from Intensive Care Unit, Universiti Malaya Medical Center (UMMC) were successfully identified as A. baumannii by ARDRA. Acinetobacter genomic species 13TU and 15TU were identified in 3 and 1 strains, respectively. ARDRA provides an accurate, rapid and definitive approach towards the identification of the species level in the genus Acinetobacter. This paper reports the first application ARDRA in genospecies identification of Acinetobacter in Malaysia.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  3. Yaseen SG, Ahmed SA, Johan MF, Kiron R, Daher AM
    Transfus Apher Sci, 2013 Dec;49(3):647-51.
    PMID: 23890575 DOI: 10.1016/j.transci.2013.07.003
    Transmission of infectious diseases is a recognized complication of blood transfusion and blood products. Nucleic acid testing (NAT) may contribute to improved efficiency of blood screening and thereby increase the safety margin for transfused blood.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  4. Teh CS, Chua KH, Lim YA, Lee SC, Thong KL
    ScientificWorldJournal, 2014;2014:457839.
    PMID: 24967435 DOI: 10.1155/2014/457839
    We have successfully developed a Loop-mediated isothermal amplification (LAMP) assay that could specifically detect generic Escherichia coli (E. coli). This assay was tested on 85 bacterial strains and successfully identified 54 E. coli strains (average threshold time, Tt = 21.26). The sensitivity of this assay was evaluated on serial dilutions of bacterial cultures and spiked faeces. The assay could detect 10(2) CFU/mL for bacterial culture with Tt = 33.30 while the detection limit for spiked faeces was 10(3) CFU/mL (Tt = 31.12). We have also detected 46 generic E. coli from 50 faecal samples obtained from indigenous individuals with 16% of the positive samples being verocytotoxin-producing E. coli (VTEC) positive. VT1/VT2 allele was present in one faecal sample while the ratio of VT1 to VT2 was 6 : 1. Overall, our study had demonstrated high risk of VTEC infection among the indigenous community and most of the asymptomatic infection occurred among those aged below 15 years. The role of asymptomatic human carriers as a source of dissemination should not be underestimated. Large scale screening of the VTEC infection among indigenous populations and the potential contamination sources will be possible and easy with the aid of this newly developed rapid and simple LAMP assay.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  5. Tan NH, Palmer R, Wang R
    J Obstet Gynaecol Res, 2010 Feb;36(1):19-26.
    PMID: 20178523 DOI: 10.1111/j.1447-0756.2009.01110.x
    Array-based comparative genomic hybridization (array CGH) is a new molecular technique that has the potential to revolutionize cytogenetics. However, use of high resolution array CGH in the clinical setting is plagued by the problem of widespread copy number variations (CNV) in the human genome. Constitutional microarray, containing only clones that interrogate regions of known constitutional syndromes, may circumvent the dilemma of detecting CNV of unknown clinical significance.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods
  6. Isa MN, Sulong S, Sidek MR, George PJ, Abdullah JM
    PMID: 15115103
    Telomerase, the enzyme that stabilizes telomere length is reactivated with almost all cancer types, and may be a useful diagnostic marker for malignancy. Telomerase activity has been detected in germ line cells and most cancer cells, whereas most normal somatic cells have no clearly detectable telomerase activity. In our study, we aim to detect telomerase activity in 20 human central nervous system tumors from Malaysian patients. Telomerase activity was detected based on a highly sensitive procedure consisting of a CHAPS detergent-based extraction from frozen tissues and a PCR-based telomeric repeat amplification protocol (TRAP) using a TRAPEZE Telomerase Detection Kit (Intergen, Co). Telomerase activity was considered positive when a ladder of products was observed starting at 50bp, with 6bp increments. The activity was detected in 30% of the samples analysed, included glioblastoma multiforme, meduloblastoma, paraganglioma and oligodendroglioma. The result of Fisher's exact test indicated that there was a significant association between telomerase activity status with tumor grade (p=0.003). These results suggest that telomerase activity may be an important marker for tumor malignancy.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods
  7. Hamidah NH, Munirah AR, Hafiza A, Farisah AR, Shuhaila A, Norzilawati MN, et al.
    Malays J Pathol, 2014 Dec;36(3):163-8.
    PMID: 25500514 MyJurnal
    Prenatal diagnosis is essential in the new era of diagnosis and management of genetic diseases in obstetrics. Multiple ligation-dependent probe amplification (MLPA) is a recent technique for prenatal diagnosis for the relative quantification of 40 different nucleic acid sequences in one single reaction. We had utilized the MLPA technique in detecting aneuploidies in amniotic fluid samples from 25 pregnant women from the Obstetrics and Gynaecology Department UKMMC, versus the quantitative fluorescent polymerase chain reaction (QF-PCR) method. Conclusive results were obtained in 18 cases and all were concordant with that of the QF-PCR. All four cases of trisomies were correctly identified including one case with maternal cell contamination.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  8. Ding CH, Ismail Z, Sulong A, Wahab AA, Gan B, Mustakim S, et al.
    Malays J Pathol, 2020 Dec;42(3):401-407.
    PMID: 33361721
    INTRODUCTION: Rifampicin is a key first-line antimycobacterial agent employed for the treatment of pulmonary tuberculosis (PTB). This study sought to obtain prevalence data on rifampicin-resistant Mycobacterium tuberculosis among smear-positive PTB patients in the Klang District of Malaysia.

    MATERIALS AND METHODS: A total of 103 patients from the Chest Clinic of Hospital Tengku Ampuan Rahimah with sputum smears positive for acid-fast bacilli were included in this cross-sectional study. All sputa were tested using Xpert MTB/RIF to confirm the presence of M. tuberculosis complex and detect rifampicin resistance. Sputa were also sent to a respiratory medicine institute for mycobacterial culture. Positive cultures were then submitted to a reference laboratory, where isolates identified as M. tuberculosis complex underwent drug susceptibility testing (DST).

    RESULTS: A total of 58 (56.3%) patients were newly diagnosed and 45 (43.7%) patients were previously treated. Xpert MTB/RIF was able to detect rifampicin resistance with a sensitivity and specificity of 87.5% and 98.9%, respectively. Assuming that a single resistant result from Xpert MTB/RIF or any DST method was sufficient to denote resistance, a total of 8/103 patients had rifampicinresistant M. tuberculosis. All eight patients were previously treated for PTB (p<0.05). The overall prevalence of rifampicin resistance among smear-positive PTB patients was 7.8%, although it was 17.8% among the previously treated ones.

    CONCLUSION: The local prevalence of rifampicin-resistant M. tuberculosis was particularly high among previously treated patients. Xpert MTB/RIF can be employed in urban district health facilities not only to diagnose PTB in smear-positive patients, but also to detect rifampicin resistance with good sensitivity and specificity.

    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  9. 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.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods
  10. Lai MY, Ooi CH, Jaimin JJ, Lau YL
    Am J Trop Med Hyg, 2020 06;102(6):1370-1372.
    PMID: 32228783 DOI: 10.4269/ajtmh.20-0001
    The incidence of zoonotic malaria, Plasmodium knowlesi, infection is increasing and now is the major cause of malaria in Malaysia. Here, we describe a WarmStart colorimetric loop-mediated isothermal amplification (LAMP) assay for the detection of Plasmodium spp. The detection limit for this assay was 10 copies/µL for P knowlesi and Plasmodium ovale and 1 copy/µL for Plasmodium falciparum, Plasmodium vivax, and Plasmodium malariae. To test clinical sensitivity and specificity, 100 microscopy-positive and 20 malaria-negative samples were used. The WarmStart colorimetric LAMP was 98% sensitive and 100% specific. Amplification products were visible for direct observation, thereby eliminating the need for post-amplification processing steps. Therefore, WarmStart colorimetric LAMP is suitable for use in resource-limited settings.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  11. Britton S, Cheng Q, Grigg MJ, William T, Anstey NM, McCarthy JS
    Am J Trop Med Hyg, 2016 07 06;95(1):120-2.
    PMID: 27162264 DOI: 10.4269/ajtmh.15-0670
    The simian parasite Plasmodium knowlesi is now the commonest cause of malaria in Malaysia and can rapidly cause severe and fatal malaria. However, microscopic misdiagnosis of Plasmodium species is common, rapid antigen detection tests remain insufficiently sensitive and confirmation of P. knowlesi requires polymerase chain reaction (PCR). Thus available point-of-care diagnostic tests are inadequate. This study reports the development of a simple, sensitive, colorimetric, high-throughput loop-mediated isothermal amplification assay (HtLAMP) diagnostic test using novel primers for the detection of P. knowlesi. This assay is able to detect 0.2 parasites/μL, and compared with PCR has a sensitivity of 96% for the detection of P. knowlesi, making it a potentially field-applicable point-of-care diagnostic tool.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  12. Mallepaddi PC, Lai MY, Podha S, Ooi CH, Liew JW, Polavarapu R, et al.
    Am J Trop Med Hyg, 2018 09;99(3):704-708.
    PMID: 29943720 DOI: 10.4269/ajtmh.18-0177
    The present study aims to develop a method for rapid diagnosis of malaria using loop-mediated isothermal amplification (LAMP) combined with a lateral flow device (LFD). By adding the biotin-labeled and fluorescein amidite-labeled loop primers to the LAMP reaction solution, the end product can be visualized on a LFD. The entire procedure takes approximately 42 minutes to complete, LAMP assay exhibited high sensitivity, as the detection limit was 0.01 pg/μL for all five Plasmodium species. It was demonstrated that all Plasmodium knowlesi (N = 90) and Plasmodium vivax (N = 56) were positively amplified by LAMP-LFD assay, whereas healthy donor samples (N = 8) were negative. However, not all mixed infections were positive, and other infected nonmalaria samples were negative. Loop-mediated isothermal amplification-LFD represents a robust approach with potential suitability for use in resource-constrained laboratories. We believe that LAMP-LFD has a potential to be developed as point-of-care diagnostic tool in future.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  13. Lai MY, Tang SN, Lau YL
    Am J Trop Med Hyg, 2021 Jun 15;105(2):375-377.
    PMID: 34129521 DOI: 10.4269/ajtmh.21-0150
    Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been spreading rapidly all over the world. In the absence of effective treatments or a vaccine, there is an urgent need to develop a more rapid and simple detection technology of COVID-19. We describe a WarmStart colorimetric reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for the detection of SARS-CoV-2. The detection limit for this assay was 1 copy/µL SARS-CoV-2. To test the clinical sensitivity and specificity of the assay, 37 positive and 20 negative samples were used. The WarmStart colorimetric RT-LAMP had 100% sensitivity and specificity. End products were detected by direct observation, thereby eliminating the need for post-amplification processing steps. WarmStart colorimetric RT-LAMP provides an opportunity to facilitate virus detection in resource-limited settings without a sophisticated diagnostic infrastructure.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  14. Lai MY, Ooi CH, Lau YL
    Am J Trop Med Hyg, 2018 03;98(3):700-703.
    PMID: 29260656 DOI: 10.4269/ajtmh.17-0738
    The aim of this study was to develop a recombinase polymerase amplification (RPA) combined with a lateral flow (LF) strip method for specific diagnosis of Plasmodium knowlesi. With incubation at 37°C, the 18S rRNA gene of P. knowlesi was successfully amplified within 12 minutes. By adding a specifically designed probe to the reaction solution, the amplified RPA product can be visualized on a LF strip. The RPA assay exhibited high sensitivity with limits of detection down to 10 parasites/μL of P. knowlesi. Nonetheless, it was demonstrated that all P. knowlesi (N = 41) and other Plasmodium sp. (N = 25) were positive while negative samples (N = 8) were negative. Therefore, a combination of RPA and LF strip detection is a highly promising approach with the potential to be suitable for use in resource-limited settings.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  15. Lai MY, Lau YL
    Am J Trop Med Hyg, 2022 Oct 12;107(4):815-819.
    PMID: 35970289 DOI: 10.4269/ajtmh.22-0136
    We developed a combination of recombinase polymerase and loop-mediated isothermal amplification methods (RAMP) for rapid screening of five human Plasmodium spp. simultaneously. RAMP is a two-stage isothermal amplification method, which consists of a first-stage recombinase polymerase amplification and a second-stage loop-mediated isothermal amplification. Under these two isothermal conditions, five Plasmodium spp. were amplified in less than 40 minutes. We demonstrated RAMP assay with 10-fold better limit of detection than a single (loop-mediated isothermal amplification) LAMP. As compared with microscopy, RAMP assay showed 100% sensitivity (95% CI: 95.65-100.00%) and 100% specificity (95% CI: 69.15-100.00%). The end products were inspected by the color changes of neutral red. Positive reactions were indicated by pink while the negative reactions remained yellow. The combination assay established in this study can be used as a routine diagnostic method for malaria.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods
  16. Lai MY, Abdul Hamid MH, Jelip J, Mudin RN, Lau YL
    Am J Trop Med Hyg, 2024 Apr 03;110(4):648-652.
    PMID: 38412548 DOI: 10.4269/ajtmh.23-0572
    Loop-mediated isothermal amplification (LAMP) is a nucleic acid amplification technique that can amplify specific nucleic acids at a constant temperature (63-65°C) within a short period (<1 hour). In this study, we report the utilization of recombinase-aided LAMP to specifically amplify the 18S sRNA of Plasmodium knowlesi. The method was built on a conventional LAMP assay by inclusion of an extra enzyme, namely recombinase, into the master mixture. With the addition of recombinase into the LAMP assay, the assay speed was executed within a time frame of less than 28 minutes at 65°C. We screened 55 P. knowlesi samples and 47 non-P. knowlesi samples. No cross-reactivity was observed for non-P. knowlesi samples, and the detection limit for recombinase-aided LAMP was one copy for P. knowlesi after LAMP amplification. It has been reported elsewhere that LAMP can be detected through fluorescent readout systems. Although such systems result in considerable limits of detection, the need for sophisticated equipment limits their use. Hence, we used here a colorimetric detection platform for the evaluation of the LAMP assay's performance. This malachite green-based recombinase-aided LAMP assay enabled visualization of results with the naked eye. Negative samples were observed by a change in color from green to colorless, whereas positive samples remained green. Our results demonstrate that the LAMP assay developed here is a convenient, sensitive, and useful diagnostic tool for the rapid detection of knowlesi malaria parasites. This method is suitable for implementation in remote healthcare settings, where centralized laboratory facilities, funds, and clinicians are in short supply.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods
  17. Nakowong P, Chatchawal P, Chaibun T, Boonapatcharoen N, Promptmas C, Buajeeb W, et al.
    Talanta, 2024 Mar 01;269:125495.
    PMID: 38043336 DOI: 10.1016/j.talanta.2023.125495
    Cervical cancer emerges as the third most prevalent types of malignancy among women on a global scale. Cervical cancer is significantly associated with the persistent infection of human papillomavirus (HPV) type 16. The process of diagnosing is crucial in order to prevent the progression of a condition into a malignant state. The early detection of cervical cancer through initial stage screening is of the utmost significance in both the prevention and effective management of this disease. The present detection methodology is dependent on quantitative polymerase chain reaction (qPCR), which necessitates the use of a costly heat cycler instrument. In this study, we report the development of an electrochemical DNA biosensor integrated with an isothermal recombinase polymerase amplification (RPA) reaction for the detection and identification of the high-risk HPV-16 genotype. The electrochemical biosensor exhibited a high degree of specificity and sensitivity, as evidenced by its limit of detection (LOD) of 0.23 copies/μL of HPV-16 DNA. The validity of this electrochemical platform was confirmed through the analysis of 40 cervical tissues samples, and the findings were consistent with those obtained through polymerase chain reaction (PCR) testing. Our straightforward electrochemical detection technology and quick turnaround time at 75 min make the assay suitable for point-of-care testing in low-resource settings.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods
  18. Chan SK, Kuzuya A, Choong YS, Lim TS
    SLAS Discov, 2019 01;24(1):68-76.
    PMID: 30063871 DOI: 10.1177/2472555218791743
    The inherent ability of nucleic acids to recognize a complementary pair has gained wide popularity in DNA sensor applications. DNA molecules can be produced in bulk and easily incorporated with various nanomaterials for sensing applications. More complex designs and sophisticated DNA sensors have been reported over the years to allow DNA detection in a faster, cheaper, and more convenient manner. Here, we report a DNA sensor designed to function like a switch to turn "on" silver nanocluster (AgNC) generation in the presence of a specific DNA target. By defining the probe region sequence, we are able to tune the color of the AgNC generated in direct relation to the different targets. As a proof of concept, we used dengue RNA-dependent RNA polymerase conserved sequences from all four serotypes as targets. This method was able to distinguish each dengue serotype by generating the serotype-respective AgNCs. The DNA switch was also able to identify and amplify the correct target in a mixture of targets with good specificity. This strategy has a detection limit of between 1.5 and 2.0 µM depending on the sequence of AgNC. The DNA switch approach provides an attractive alternative for single-target or multiplex DNA detection.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  19. Lau YL, Lai MY, Teoh BT, Abd-Jamil J, Johari J, Sam SS, et al.
    PLoS One, 2015;10(9):e0138694.
    PMID: 26384248 DOI: 10.1371/journal.pone.0138694
    Dengue is usually diagnosed by isolation of the virus, serology or molecular diagnostic methods. Several commercial kits for the diagnosis of dengue are existing, but concerns have arisen regarding to the affordability and performance characteristics of these kits. Hence, the loop-mediated isothermal amplification (LAMP) is potentially ideal to be used especially in resource limited environments. Serum was collected from healthy donors and patients diagnosed with dengue infection. RNA extracted from the serum samples were tested by reverse-transcription-LAMP assay developed based on 3'-NCR gene sequences for DENV 1-4. Results were interpreted by a turbidity meter in real time or visually at the end of the assay. Sensitivity and specificity of RT-LAMP results were calculated and compared to qRT-PCR and ELISA. RT-LAMP is highly sensitive with the detection limit of 10 RNA copies for all serotypes. Dengue virus RNA was detected in all positive samples using RT-LAMP and none of the negative samples within 30-45 minutes. With continuing efforts in the optimization of this assay, RT-LAMP may provide a simple and reliable test for detecting DENV in areas where dengue is prevalent.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods*
  20. Lau YL, Ismail IB, Mustapa NIB, Lai MY, Tuan Soh TS, Haji Hassan A, et al.
    PLoS One, 2021;16(1):e0245164.
    PMID: 33406112 DOI: 10.1371/journal.pone.0245164
    Rapid diagnosis is an important intervention in managing the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) outbreak. Real time reverse transcription polymerase chain reaction (RT-qPCR) remains the primary means for diagnosing the new virus strain but it is time consuming and costly. Recombinase polymerase amplification (RPA) is an isothermal amplification assay that does not require a PCR machine. It is an affordable, rapid, and simple assay. In this study, we developed and optimized a sensitive reverse transcription (RT)-RPA assay for the rapid detection of SARS-CoV-2 using SYBR Green I and/or lateral flow (LF) strip. The analytical sensitivity and specificity of the RT-RPA assay were tested by using 10-fold serial diluted synthetic RNA and genomic RNA of similar viruses, respectively. Clinical sensitivity and specificity of the RT-RPA assay were carried out using 78 positive and 35 negative nasopharyngeal samples. The detection limit of both RPA and RT-qPCR assays was 7.659 and 5 copies/μL RNA, respectively with no cross reactivity with other viruses. The clinical sensitivity and specificity of RT-RPA were 98% and 100%, respectively. Our study showed that RT-RPA represents a viable alternative to RT-qPCR for the detection of SARS-CoV-2, especially in areas with limited infrastructure.
    Matched MeSH terms: Nucleic Acid Amplification Techniques/methods
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