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Fulltext Safety and immunogenicity of a tetravalent dengue vaccine in healthy children aged 2-11 years in Malaysia: a randomized, placebo-controlled, Phase III study

Hss AS, Koh MT, Tan KK, Chan LG, Zhou L, Bouckenooghe A, et al.

Vaccine, 2013 Dec 2;31(49):5814-21.
PMID: 24135573 DOI: 10.1016/j.vaccine.2013.10.013

Dengue disease is a major public health problem across the Asia-Pacific region for which there is no licensed vaccine or treatment. We evaluated the safety and immunogenicity of Phase III lots of a candidate vaccine (CYD-TDV) in children in Malaysia.
Influenza vaccine concurrently administered with a combination measles, mumps, and rubella vaccine to young children

Lum LC, Borja-Tabora CF, Breiman RF, Vesikari T, Sablan BP, Chay OM, et al.

Vaccine, 2010 Feb 10;28(6):1566-74.
PMID: 20003918 DOI: 10.1016/j.vaccine.2009.11.054

Children aged 11 to <24 months received 2 intranasal doses of live attenuated influenza vaccine (LAIV) or placebo, 35+/-7 days apart. Dose 1 was administered concomitantly with a combined measles, mumps, and rubella vaccine (Priorix). Seroresponses to measles and mumps were similar between groups. Compared with placebo, response rates to rubella in LAIV+Priorix recipients were statistically lower at a 15 IU/mL threshold (83.9% vs 78.0%) and the prespecified noninferiority criteria were not met. In a post hoc analysis using an alternate widely accepted threshold of 10 IU/mL, the noninferiority criteria were met (93.4% vs 89.8%). Concomitant administration with Priorix did not affect the overall influenza protection rate of LAIV (78.4% and 63.8% against antigenically similar influenza strains and any strain, respectively).
Vector competence of Malaysian Aedes albopictus with and without Wolbachia to four dengue virus serotypes

Joanne S, Vythilingam I, Teoh BT, Leong CS, Tan KK, Wong ML, et al.

Trop Med Int Health, 2017 09;22(9):1154-1165.
PMID: 28653334 DOI: 10.1111/tmi.12918

OBJECTIVE: To determine the susceptibility status of Aedes albopictus with and without Wolbachia to the four dengue virus serotypes.
METHODS: Two newly colonised colonies of Ae. albopictus from the wild were used for the study. One colony was naturally infected with Wolbachia while in the other Wolbachia was removed by tetracycline treatment. Both colonies were orally infected with dengue virus-infected fresh blood meal. Dengue virus load was measured using quantitative RT-PCR at four-time intervals in the salivary glands, midguts and ovaries.
RESULTS: Wolbachia did not significantly affect Malaysian Ae. albopictus dengue infection or the dissemination rate for all four dengue virus serotypes. Malaysian Ae. albopictus had the highest replication kinetics for DENV-1 and the highest salivary gland and midgut infection rate for DENV-4.
CONCLUSION: Wolbachia, which naturally exists in Malaysian Ae. albopictus, does not significantly affect dengue virus replication. Malaysian Ae. albopictus is susceptible to dengue virus infections and capable of transmitting dengue virus, especially DENV-1 and DENV-4. Removal of Wolbachia from Malaysian Ae. albopictus would not reduce their susceptibility status.
Multiplex sequencing of SARS-Cov-2 genome directly from clinical samples using the Ion Personal Genome Machine (PGM)

Tan KK, Tiong V, Tan JY, Wong JE, Teoh BT, Abd-Jamil J, et al.

Trop Biomed, 2021 Sep 01;38(3):283-288.
PMID: 34362871 DOI: 10.47665/tb.38.3.069

Various methods have been developed for rapid and high throughput full genome sequencing of SARS-CoV-2. Here, we described a protocol for targeted multiplex full genome sequencing of SARS-CoV-2 genomic RNA directly extracted from human nasopharyngeal swabs using the Ion Personal Genome Machine (PGM). This protocol involves concomitant amplification of 237 gene fragments encompassing the SARS-CoV-2 genome to increase the abundance and yield of viral specific sequencing reads. Five complete and one near-complete genome sequences of SARS-CoV-2 were generated with a single Ion PGM sequencing run. The sequence coverage analysis revealed two amplicons (positions 13 751-13 965 and 23 941-24 106), which consistently gave low sequencing read coverage in all isolates except 4Apr20-64- Hu. We analyzed the potential primer binding sites within these low covered regions and noted that the 4Apr20-64-Hu possess C at positions 13 730 and 23 929, whereas the other isolates possess T at these positions. The genome nucleotide variations observed suggest that the naturally occurring variations present in the actively circulating SARS-CoV-2 strains affected the performance of the target enrichment panel of the Ion AmpliSeq™ SARS CoV 2 Research Panel. The possible impact of other genome nucleotide variations warrants further investigation, and an improved version of the Ion AmpliSeq™ SARS CoV 2 Research Panel, hence, should be considered.
Evaluation of commercial serological assays in Malaysia for detection of anti-Zika virus antibodies

Khoo HY, Lee HY, Khor CS, Tan KK, AbuBakar S

Trop Biomed, 2021 Dec 01;38(4):613-621.
PMID: 35001928 DOI: 10.47665/tb.38.4.105

The recommended test guidelines for Zika virus (ZIKV) include using both molecular and serological tools. While the molecular tools are useful for detecting acute infection, the serological tools are useful for the detection of previous infections. Nevertheless, detection of ZIKV-specific antibodies remains a challenge due to the high cross-reactivity between ZIKV and other flaviviruses such as dengue virus (DENV) and Japanese encephalitis virus (JEV). The objective of this study is to evaluate the commercially available enzyme-linked immunosorbent assay (ELISA) for the detection of ZIKV IgG. In this study, we evaluated 6 commercially available anti-ZIKV IgG ELISA kits. Pre-characterized serum panels consisting of 70 sera were selected for the evaluation. The diagnostic accuracy of each ELISA kits was determined and compared to the gold standard, Foci Reduction Neutralization Test (FRNT). The present study established that the performance of the NS1-based anti-ZIKV IgG ELISA kit was superior to that which uses of the E protein as antigen. Overall, commercial ZIKV IgG ELISA showed varying test performances, with some achieving moderate to high test sensitivities and specificities. When compared against the FRNT, the test sensitivities ranged from 7.1% to 78.6%, whereas, the test specificities ranged from 40.0% to 100%. Limitation to the study includes the cross reactivity between flavivirus and specificity of the kit in addressing the cross reactivity.
Development of a TaqMan minor groove binding probe-based quantitative reverse transcription polymerase chain reaction for the detection and quantification of Zika virus

Chin KL, Teoh BT, Sam SS, Loong SK, Tan KK, Azizan NS, et al.

Trop Biomed, 2022 Dec 01;39(4):518-523.
PMID: 36602210 DOI: 10.47665/tb.39.4.005

Zika virus (ZIKV) infection has emerged as a global health concern following epidemic outbreaks of severe neurological disorders reported in Pacific and Americas since 2016. Therefore, a rapid, sensitive and specific diagnostic test for ZIKV infection is critical for the appropriate patient management and the control of disease spread. A TaqMan minor groove binding (MGB) probe-based quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay was developed based on the conserved sequence regions of 463 ZIKV NS2B genes. The designed ZIKV qRT-PCR assay was evaluated for its detection limit, strain coverage and cross-reactivity. We further assessed the clinical applicability of qRT-PCR assay for ZIKV RNA detection using a total 18 simulated clinical specimens. The detection limit of the qRT-PCR assay was 11.276 ZIKV RNA copies at the 95% probability level (probit analysis, p<= 0.05). Both Asian and African ZIKV strains were detected by the qRT-PCR assay without cross-reacting with DENV-1, DENV-2, DENV-3, DENV-4, CHIKV, JEV, LGTV, GETV and SINV. The qRT-PCR assay demonstrated a perfect agreement (k = 1.000, P < 0.001) with the reference assay; the sensitivity and specificity of the qRT-PCR assay were 100% (95% CI= 79.6-100) and 100% (95% CI= 43.9-100) respectively. The qRT-PCR assay developed in this study is a useful diagnostic tool for the broad coverage detection and quantification of both the Asian and African ZIKV strains.
Snake bite in Kelantanese children: a five year experience

Tan KK, Choo KE, Ariffin WA

Toxicon, 1990;28(2):225-30.
PMID: 2339437

The records associated with 83 children from 16 months to 12 years of age who were admitted with snake bite to Kota Bharu General Hospital and University Hospital, Universiti Sains Malaysia over a 5 year period were reviewed. Elapid bites were more common than viper bites while sea-snake bites were not recorded. Symptoms were relatively mild, the common clinical features being pain and local swelling. Antivenom therapy was required in 11 children. Only three of the 11 children developed minor adverse reactions to antivenom. Four of the 83 required ventilatory support for respiratory failure and two children died.
Posterolateral spinal fusion with ostegenesis induced BMSC seeded TCP/HA in a sheep model

Shamsul BS, Tan KK, Chen HC, Aminuddin BS, Ruszymah BH

Tissue Cell, 2014 Apr;46(2):152-8.
PMID: 24630213 DOI: 10.1016/j.tice.2014.02.001

Autogenous bone graft is the gold standard for fusion procedure. However, pain at donor site and inconsistent outcome have left a surgeon to venture into some other technique for spinal fusion. The objective of this study was to determine whether osteogenesis induced bone marrow stem cells with the combination of ceramics granules (HA or TCP/HA), and fibrin could serve as an alternative to generate spinal fusion. The sheep's bone marrow mesenchymal stem cells (BMSCs) were aspirated form iliac crest and cultured for several passages until confluence. BMSCs were trypsinized and seeded on hydroxyapatite scaffold (HA) and tricalcium phosphate/hydroxyapatite (TCP/HA) for further osteogenic differentiation in the osteogenic medium one week before implantation. Six adult sheep underwent three-level, bilateral, posterolateral intertransverse process fusions at L1-L6. Three fusion sites in each animal were assigned to three treatments: (a) HA constructs group/L1-L2, (b) TCP/HA constructs group/L2-L3, and (c) autogenous bone graft group/L5-L6. The spinal fusion segments were evaluated using radiography, manual palpation, histological analysis and scanning electron microscopy (SEM) 12 weeks post implantation. The TCP/HA constructs achieved superior lumbar intertransverse fusion compared to HA construct but autogenous bone graft still produced the best fusion among all.
Fulltext Bacterial community in Haemaphysalis ticks of domesticated animals from the Orang Asli communities in Malaysia

Khoo JJ, Chen F, Kho KL, Ahmad Shanizza AI, Lim FS, Tan KK, et al.

Ticks Tick Borne Dis, 2016 07;7(5):929-937.
PMID: 27132518 DOI: 10.1016/j.ttbdis.2016.04.013

Ticks are vectors in the transmission of many important infectious diseases in human and animals. Ticks can be readily found in the semi-forested areas such as the settlements of the indigenous people in Malaysia, the Orang Asli. There is still minimal information available on the bacterial agents associated with ticks found in Malaysia. We performed a survey of the bacterial communities associated with ticks collected from domestic animals found in two Orang Asli villages in Malaysia. We collected 62 ticks, microscopically and molecularly identified as related to Haemaphysalis wellingtoni, Haemaphysalis hystricis and Haemaphysalis bispinosa. Bacterial 16s rRNA hypervariable region (V6) amplicon libraries prepared from the tick samples were sequenced on the Ion Torrent PGM platform. We detected a total of 392 possible bacterial genera after pooling and sequencing 20 samples, indicating a diverse bacterial community profile. Dominant taxa include the potential tick endosymbiont, Coxiella. Other dominant taxa include the tick-associated pathogen, Rickettsia, and environmental bacteria such as Bacillus, Mycobacterium, Sphingomonas and Pseudomonas. Other known tick-associated bacteria were also detected, including Anaplasma, Ehrlichia, Rickettsiella and Wolbachia, albeit at very low abundance. Specific PCR was performed on selected samples to identify Rickettsia and Coxiella. Sequence of Rickettsia felis, which causes spotted fever in human and cats, was identified in one sample. Coxiella endosymbionts were detected in three samples. This study provides the baseline knowledge of the microbiome of ticks in Malaysia, focusing on tick-associated bacteria affecting the Orang Asli communities. The role of the herein found Coxiella and Rickettsia in tick physiology or disease transmission merits further investigation.
Bacterial communities in Haemaphysalis, Dermacentor and Amblyomma ticks collected from wild boar of an Orang Asli Community in Malaysia

Lim FS, Khoo JJ, Tan KK, Zainal N, Loong SK, Khor CS, et al.

Ticks Tick Borne Dis, 2020 03;11(2):101352.
PMID: 31866439 DOI: 10.1016/j.ttbdis.2019.101352

Ticks are hematophagous vectors of arthropod-borne disease agents globally. In Malaysia, despite seroprevalence studies indicating the presence of tick-borne diseases among the indigenous people, the etiological agents of these diseases are still unclear. These indigenous people, also known as the Orang Asli, still live in forested areas with frequent contact with wildlife. Wild boar are ubiquitously found in the forested areas where the Orang Asli communities are located and are commonly hunted as a food supplement. In this study, we aim to determine the tick species parasitizing wild boar from an Orang Asli community, and explore the tick-associated bacterial communities using 16 s rRNA amplicon sequencing on the Ion Torrent PGM™ platform. A total of 72 ticks were collected from three wild boar and were morphologically identified as Haemaphysalis hystricis (n = 32), Dermacentor compactus (n = 15), Amblyomma testudinarium (n = 13), Dermacentor steini (n = 10) and Dermacentor atrosignatus (n = 2). Across all tick samples, 910 bacterial taxa were identified. Although the bacterial communities were not significantly distinct between tick species in beta-diversity analyses, Coxiella, Rickettsia and Francisella were detected at high relative abundance in H. hystricis, D. compactus and D. steini respectively. Many other bacterial genera, including those that have been described in many different tick species, were also identified, including Pseudomonas, Acinetobacter, Staphylococcus and Corynebacterium. Beta-diversity analyses also showed that the bacterial communities were separated based on the animal host from which the ticks were collected from, suggesting that the bacterial communities here may be influenced by the animal skin microflora, host blood or the environment. PCR screening confirmed the presence of Rickettsia sp. related to spotted fever group Rickettsia in some of the ticks. This study provides baseline knowledge of the microbiome of H. hystricis, D. atrosignatus, D. compactus, D. steini and A. testudinarium parasitizing wild boar in this region. The information gained in this study provides the basis to target our efforts in H. hystricis, D. compactus and D. steini for the future investigation of vector competence and the zoonotic potential for the Coxiella, Rickettsia and Francisella detected here, as well as their implications for the risks of tick-borne diseases among the Orang Asli communities.
Fulltext Clinical comparison of HMPV and RSV infections in hospitalised Malaysian children: A propensity score matched study

Ng DC, Liew CH, Tan KK, Awang EHB, Nazri FNBA, Maran AKT, et al.

Clin Respir J, 2024 Mar;18(3):e13747.
PMID: 38529669 DOI: 10.1111/crj.13747

INTRODUCTION: Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are significant contributors to the burden of acute respiratory infections in children, but data on hMPV from Southeast Asia are limited despite its potential for serious disease. This study aimed to compare the clinical presentation, resource utilisation and outcomes between hMPV and RSV infections in hospitalised Malaysian children.
METHODS: This retrospective, observational study included children aged ≤12 years old hospitalised with hMPV or RSV, confirmed via direct fluorescent antibody (DFA) methods, between 1 July to 30 October 2022 at Hospital Tuanku Ja'afar Seremban, Malaysia. Demographic, clinical presentation, resource utilisation and outcome data were analysed. Propensity score matching was used to balance cohorts based on key demographic and clinical characteristics.
RESULTS: This study included 192 patients, comprising 112 with hMPV and 80 with RSV. hMPV patients were older (median age 20.5 vs. 9.4 months, p
Importance of a thorough examination

Pau WS, Tan KK

Pediatr Infect Dis J, 2008 Jun;27(6):569-70.
PMID: 18449061 DOI: 10.1097/INF.0b013e318168db08

Scrub typhus is a common cause of febrile illness among children from rural regions in tropical countries. We described 2 cases of scrub typhus with an eschar localized in the genitalia that was missed during the routine medical examination of a febrile child.
Fulltext Prevention is better than cure

Andrew Tan KK

Med J Malaysia, 2014 Feb;69(1):1.
PMID: 24814619

No abstract available.
Fulltext Outcomes Following Surgery for Distal Rectal Cancers: A Comparison between Laparoscopic and Open Abdomino-Perineal Resection

Tan KK, Chong CS, Tsang CB, Koh DC

Med J Malaysia, 2013 Aug;68(4):348-52.
PMID: 24145265

Oncologic outcomes following laparoscopic abdomino-perineal resection (APR) for distal rectal cancer are infrequently reported. This study aims to compare the long term outcomes between laparoscopic and open APR in distal rectal cancers.
Fulltext Management of isolated splenic injuries after blunt trauma: an institution's experience over 6 years

Tan KK, Chiu MT, Vijayan A

Med J Malaysia, 2010 Dec;65(4):304-6.
PMID: 21901951

Forty-two patients with traumatic blunt splenic injuries were admitted over a six year period. Vehicular-related collisions and fall from height accounted for the injuries in 38 (90.5%) of them. Eleven (26.2%) underwent immediate surgery (7 splenectomy and 4 splenorrhaphy), while the remaining 31 patients were treated nonoperatively of which 3 underwent angio-embolisation. Twenty seven patients had either grade III or IV splenic injuries. Operative management was more likely in patients with lower haemoglobin or with more severe splenic injury. Nonoperative management can be adopted in patients with blunt isolated splenic injuries but operative management is still indispensable in certain instances.
Fulltext Bone graft substitute using hydroxyapatite scaffold seeded with tissue engineered autologous osteoprogenitor cells in spinal fusion: early result in a sheep model

Tan KK, Tan GH, Shamsul BS, Chua KH, Ng MHA, Ruszymah BHI, et al.

Med J Malaysia, 2005 Jul;60 Suppl C:53-8.
PMID: 16381285

Spinal fusion using autologous bone graft is performed in an increasing rate for many spinal disorders. However, graft harvesting procedure is associated with prolonged operation time and potential donor site morbidity. We produced an engineered 'bone graft' substitute by using porous hydroxyapatite (HA) scaffold seeded with autologous bone marrow osteoprogenitor cells (OPCs) and fibrin. This obviates bone graft harvesting, thus eliminates donor site morbidity and shortens the operation time. The aim of this study is to evaluate Hydroxyapatite (HA) ceramics as scaffold for autologous tissue engineered bone construct for spinal fusion in a sheep model. The sheep's marrow was aspirated from iliac crest. The bone marrow mesenchymal stem cells (BMMSCs) were cultured for several passages in the presence of growth and differentiation factors to increase the number of OPCs. After the cultures reached confluence, they were trypsinized and seeded on Hydroxyapatite scaffold (HA). Approximately 5 million cells were generated after 3 weeks of culture. Microscopically, very tight Colony Forming Units (CFU-Fs) were seen on monolayer culture. The Von Kossa and Alizarin Red staining of monolayer culture showed positive mineralization areas; indicating the presence of OPCs. Sheep underwent a posterolateral spinal fusion in which scaffolds with or without OPCs seeded were implanted on both sides of the lumbar spine (L1-L2). Intended fusion segments were immobilized using wires. At the end of third month, the fusion constructs were harvested for histological examination. Fibrous tissue infiltration found in the inter-connecting pores of plain HA ceramics indicates inefficient new bone regeneration. New bone was found surrounding the HA ceramics seeded with autologous cells. The new bone is probably formed by the sheep BMMSCs that were initially encapsulating HA while it remained intact. The new bone is naturally fused with the vertebrae. In conclusion, the incorporation of autologous bone marrow cells improved the effectiveness of HA ceramics as 'bone graft' substitute for spinal fusion.
Fulltext Progressive supra-axial cervical instability in Down syndrome: a case report emphasising the role of extended short-segment fusion

Tan GH, Tan KK, Afian MS, Liew WF, Mohamad AR

Med J Malaysia, 2005 Jul;60 Suppl C:111-3.
PMID: 16381295

We report a case of upper cervical instability associated with Down syndrome to highlight its potential progression to inflict cord compression and the rationale for surgical decompression and extended short segment occipito-axial fusion.
Evaluation of suitable biodegradable scaffolds for engineered bone tissue

Phang MY, Ng MH, Tan KK, Aminuddin BS, Ruszymah BH, Fauziah O

Med J Malaysia, 2004 May;59 Suppl B:198-9.
PMID: 15468886

Tricalcium phosphate/hydroxyapatite (TCP/HA), hydroxyapatite (HA), chitosan and calcium sulphate (CaSO4) were studied and evaluated for possible bone tissue engineered construct acting as good support for osteogenic cells to proliferate, differentiate, and eventually spread and integrate into the scaffold. Surface morphology visualized by SEM showed that scaffold materials with additional fibrin had more cell densities attached than those without, depicting that the presence of fibrin and collagen fibers were truly a favourite choice of cells to attach. In comparison of various biomaterials used incorporated with fibrin, TCP/HA had the most cluster of cells attached.
Strategy for generating tissue-engineered human bone construct

Tan KK, Aminuddin BS, Tan GH, Sabarul Afian M, Ng MH, Fauziah O, et al.

Med J Malaysia, 2004 May;59 Suppl B:43-4.
PMID: 15468810

The strategy used to generate tissue-engineered bone construct, in view of future clinical application is presented here. Osteoprogenitor cells from periosteum of consenting scoliosis patients were isolated. Growth factors viz TGF-B2, bFGF and IGF-1 were used in concert to increase cell proliferation during in vitro cell expansion. Porous tricalcium phosphate (TCP)-hydroxyapatite (HA) scaffold was used as the scaffold to form 3D bone construct. We found that the addition of growth factors, greatly increased cell growth by 2 to 7 fold. TCP/HA proved to be the ideal scaffold for cell attachment and proliferation. Hence, this model will be further carried out on animal trial.
The use of bone marrow stem cells for bone tissue engineering

Ng MH, Aminuddin BS, Tan KK, Tan GH, Sabarul Afian M, Ruszymah BH

Med J Malaysia, 2004 May;59 Suppl B:41-2.
PMID: 15468809

Bone marrow stem cells (BMSC), known for its multipotency to differentiate into various mesenchymal cells such as chodrocyte, osteoblasts, adipocytes, etc, have been actively applied in tissue engineering. BMSC have been successfully isolated from bone marrow aspirate and bone marrow scraping from patients of various ages (13-56 years) with as little as 2ml to 5ml aspirate. BMSC isolated from our laboratory showed the presence of a heterogenous population that showed varying prevalence of surface antigens and the presence of telomerase activity albeit weak. Upon osteogenic induction, alkaline phosphatase activity and mineralization activity were observed.

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