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  1. Fulltext Distribution of the Duffy genotypes in Malaysian Borneo and its relation to Plasmodium knowlesi malaria susceptibility
    de Silva JR, Amir A, Lau YL, Ooi CH, Fong MY
    PLoS One, 2019;14(9):e0222681.
    PMID: 31536563 DOI: 10.1371/journal.pone.0222681
    The Duffy blood group plays a key role in Plasmodium knowlesi and Plasmodium vivax invasion into human erythrocytes. The geographical distribution of the Duffy alleles differs between regions with the FY*A allele having high frequencies in many Asian populations, the FY*B allele is found predominately in European populations and the FY*Bes allele found predominantly in African regions. A previous study in Peninsular Malaysia indicated high homogeneity of the dominant FY*A/FY*A genotype. However, the distribution of the Duffy genotypes in Malaysian Borneo is currently unknown. In the present study, the distribution of Duffy blood group genotypes and allelic frequencies among P. knowlesi infected patients as well as healthy individuals in Malaysian Borneo were determined. A total of 79 P. knowlesi patient blood samples and 76 healthy donor samples were genotyped using allele specific polymerase chain reaction (ASP-PCR). Subsequently a P. knowlesi invasion assay was carried out on FY*AB/ FY*A and FY*A/ FY*A Duffy genotype blood to investigate if either genotype conferred increased susceptibility to P. knowlesi invasion. Our results show almost equal distribution between the homozygous FY*A/FY*A and heterozygous FY*A/FY*B genotypes. This is in stark contrast to the Duffy distribution in Peninsular Malaysia and the surrounding Southeast Asian region which is dominantly FY*A/FY*A. The mean percent invasion of FY*A/FY*A and FY*A/FY*B blood was not significantly different indicating that neither blood group confers increased susceptibility to P. knowlesi invasion.
  2. Fulltext Plasma Ceramides as Prognostic Biomarkers and Their Arterial and Myocardial Tissue Correlates in Acute Myocardial Infarction
    de Carvalho LP, Tan SH, Ow GS, Tang Z, Ching J, Kovalik JP, et al.
    JACC Basic Transl Sci, 2018 Apr;3(2):163-175.
    PMID: 30062203 DOI: 10.1016/j.jacbts.2017.12.005
    We identified a plasma signature of 11 C14 to C26 ceramides and 1 C16 dihydroceramide predictive of major adverse cardiovascular events in patients with acute myocardial infarction (AMI). Among patients undergoing coronary artery bypass surgery, those with recent AMI, compared with those without recent AMI, showed a significant increase in 5 of the signature's 12 ceramides in plasma but not simultaneously-biopsied aortic tissue. In contrast, a rat AMI model, compared with sham control, showed a significant increase in myocardial concentrations of all 12 ceramides and up-regulation of 3 ceramide-producing enzymes, suggesting ischemic myocardium as a possible source of this ceramide signature.
  3. Prognostic Implications of Dual Platelet Reactivity Testing in Acute Coronary Syndrome
    de Carvalho LP, Fong A, Troughton R, Yan BP, Chin CT, Poh SC, et al.
    Thromb. Haemost., 2018 02;118(2):415-426.
    PMID: 29443374 DOI: 10.1160/TH17-08-0564
    Studies on platelet reactivity (PR) testing commonly test PR only after percutaneous coronary intervention (PCI) has been performed. There are few data on pre- and post-PCI testing. Data on simultaneous testing of aspirin and adenosine diphosphate antagonist response are conflicting. We investigated the prognostic value of combined serial assessments of high on-aspirin PR (HASPR) and high on-adenosine diphosphate receptor antagonist PR (HADPR) in patients with acute coronary syndrome (ACS). HASPR and HADPR were assessed in 928 ACS patients before (initial test) and 24 hours after (final test) coronary angiography, with or without revascularization. Patients with HASPR on the initial test, compared with those without, had significantly higher intraprocedural thrombotic events (IPTE) (8.6 vs. 1.2%, p ≤ 0.001) and higher 30-day major adverse cardiovascular and cerebrovascular events (MACCE; 5.2 vs. 2.3%, p = 0.05), but not 12-month MACCE (13.0 vs. 15.1%, p = 0.50). Patients with initial HADPR, compared with those without, had significantly higher IPTE (4.4 vs. 0.9%, p = 0.004), but not 30-day (3.5 vs. 2.3%, p = 0.32) or 12-month MACCE (14.0 vs. 12.5%, p = 0.54). The c-statistic of the Global Registry of Acute Coronary Events (GRACE) score alone, GRACE score + ASPR test and GRACE score + ADPR test for discriminating 30-day MACCE was 0.649, 0.803 and 0.757, respectively. Final ADPR was associated with 30-day MACCE among patients with intermediate-to-high GRACE score (adjusted odds ratio [OR]: 4.50, 95% confidence interval [CI]: 1.14-17.66), but not low GRACE score (adjusted OR: 1.19, 95% CI: 0.13-10.79). In conclusion, both HASPR and HADPR predict ischaemic events in ACS. This predictive utility is time-dependent and risk-dependent.
  4. Ocular presentations and toxoplasma serology
    Zurainee MN, Khairul Anuar A, Fong MY, Hoh HB, Choon J, Rahmah N
    JUMMEC, 2000;5:98-102.
    During the period 1996-1998, 134 patients suspected of having ocular toxoplasmosis were seen in the Ophthalmology Clinic of the University Hospital, Kuala Lumpur. Clinical presentations in these patients ranged from poor vision to severe retinal detachment. Of these patients, 72% were confirmed positive for Toxoplasma gondii infection by serological methods. Chorioretinjtis and vitritis were found to be the most apparent symptoms, both having 100%correlation with serological positivity, This was followed by uveitis, floaters, and retinal detachment with correlation at 78%, 75%and 75%, respectively. However, there was no correlation between level of serotitre and ocular presentations. KEYWORDS: Toxoplasmosis, serology, chorioretinitis, uveitis
  5. Cirian fiziko-kimia dan pengaruh ke atas ketidakstabilan bahan bumi cerun di kawasan Puchong, Selangor
    Zulfahmi Ali Rahman, Sahibin Abdul Rahim, Wan Mohd Razi Idris, Nai CF, Jasni Yaakob
    Sains Malaysiana, 2009;38.
    Tinjauan sepanjang lebuhraya Puchong-Kajang telah dijalankan khususnya di kawasan Puchong, Selangor. Terdapat 12 stesen telah dilawati dan 6 daripadanya telah dilakukan pensampelan tanah bagi analisis makmal. Cerun-cerun yang terbabit dengan pensampelan ini melibatkan cerun jenis tanih dengan julat darjah luluhawa di antara gred IV dan VI. Sampel-sampel tanih yang diambil mewakili cerun yang mengalami kegagalan dan cerun yang stabil. Ciri-ciri fiziko-kimia tanih yang dikaji melibatkan kandungan air segar dan dalam keadaan tepu, kandungan bahan organik, taburan saiz zarah, ketumpatan pukal dan sebenar, keporosan tanah, serakan liat, pH dan kandungan oksida ferum. Kandungan air tanah segar menunjukkan peratusan yang lebih tinggi pada cerun gagal berbanding cerun yang stabil. Semua sampel menunjukkan kandungan air tanah lapangan di bawah tahap kandungan air tepu. Kandungan bahan organik adalah sangat rendah (<2%) dan tanah boleh dikelaskan sebagai berpotensi tidak stabil. Terdapat hubungan positif yang jelas antara kandungan air dan bahan organik khususnya pada cerun gagal. Porositi tanah menunjukkan perkaitan positif terhadap lempung dan kandungan bahan organik. Kebanyakan tanah dikelaskan sebagai bertekstur lempung berpasir berbanding tekstur lain. Nilai-nilai koefisien serakan liat menunjukkan struktur tanah berada dalam kategori stabil hingga sangat stabil berbanding satu stesen yang dikelaskan sebagai tidak stabil. Secara umumnya, tanah terdiri daripada jenis asidik (pH4.87 - pH4.34) dengan kehadiran oksida ferum kurang daripada 6%.
  6. Fulltext Stepwise evolution of pandrug-resistance in Klebsiella pneumoniae
    Zowawi HM, Forde BM, Alfaresi M, Alzarouni A, Farahat Y, Chong TM, et al.
    Sci Rep, 2015;5:15082.
    PMID: 26478520 DOI: 10.1038/srep15082
    Carbapenem resistant Enterobacteriaceae (CRE) pose an urgent risk to global human health. CRE that are non-susceptible to all commercially available antibiotics threaten to return us to the pre-antibiotic era. Using Single Molecule Real Time (SMRT) sequencing we determined the complete genome of a pandrug-resistant Klebsiella pneumoniae isolate, representing the first complete genome sequence of CRE resistant to all commercially available antibiotics. The precise location of acquired antibiotic resistance elements, including mobile elements carrying genes for the OXA-181 carbapenemase, were defined. Intriguingly, we identified three chromosomal copies of an ISEcp1-bla(OXA-181) mobile element, one of which has disrupted the mgrB regulatory gene, accounting for resistance to colistin. Our findings provide the first description of pandrug-resistant CRE at the genomic level, and reveal the critical role of mobile resistance elements in accelerating the emergence of resistance to other last resort antibiotics.
  7. Product spectrum analysis and microbial insights of medium-chain fatty acids production from waste biomass during liquor fermentation process: Effects of substrate concentrations and fermentation modes
    Zhao J, Ma H, Wu W, Ali Bacar M, Wang Q, Gao M, et al.
    Bioresour Technol, 2023 Jan;368:128375.
    PMID: 36414142 DOI: 10.1016/j.biortech.2022.128375
    Substrate toxicity would limit the upgrading of waste biomass to medium-chain fatty acids (MCFAs). In this work, two fermentation modes of electro-fermentation (EF) and traditional fermentation (TF) with different concentration of liquor fermentation waste (20%, 40%, 60%) were used for MCFAs production as well as mechanism investigation. The highest caproate (4.04 g/L) and butyrate (13.96 g/L) concentrations were obtained by EF at 40% substrate concentration. TF experiments showed that the substrate concentration above 40% severely inhibited ethanol oxidation and products formation. Compared with TF mode, the total substrates consumption and product yields under EF mode were significantly increased by 2.6%-43.5% and 54.0%-83.0%, respectively. Microbial analysis indicated that EF effectively alleviated substrate toxicity and enriched chain elongation bacteria, particularly Clostridium_sensu_stricto 12, thereby promoting ethanol oxidation and products formation. Caproiciproducens tolerated high-concentration substrates to ensure normal lactate metabolism. This study provides a new way to produce MCFAs from high concentration wastewater.
  8. Central serous chorioretinopathy: updates in the pathogenesis, diagnosis and therapeutic strategies
    Zhang X, Lim CZF, Chhablani J, Wong YM
    Eye Vis (Lond), 2023 Jul 11;10(1):33.
    PMID: 37430344 DOI: 10.1186/s40662-023-00349-y
    Central serous chorioretinopathy (CSCR), first described by Albrecht von Graefe in 1866, is characterized by focal serous detachment of the neural retina and/or retinal pigment epithelium (RPE) in the posterior pole. CSCR is the first ever described pachychoroid disease. Most recently, hypothetical venous overload choroidopathy is also proposed due to its distinguished morphological and pathological characteristics, including choroidal thickening, choriocapillaris hyperpermeability, remodelling, and intervortex venous anastomoses. Identification of genetic variants is necessary to comprehend the pathophysiology of CSCR. The novel multimodality imaging platforms, including the ultra-widefield imaging system, flavoprotein fluorescence, fluorescence lifetime imaging ophthalmoscopy, and multispectral imaging system, have been used for diagnosing and managing CSCR. Half-dose photodynamic therapy (PDT) remains the mainstay of clinical practice, with about 95% of patients with chronic CSCR improving to visual acuity (VA) of 20/30 or better. The use of oral eplerenone for routine clinical care remains controversial, and long-term randomized clinical trials are warranted to investigate its efficacy in acute and chronic CSCR. While CSCR has generally been recognized as a self-limiting disease with good prognosis, the underlying pathogenesis is still not fully understood, and treatments are often not fully effective. With new evidence emerging about pachydrusen being a disease precursor in both CSCR and polypoidal choroidal vasculopathy (PCV), it would be interesting to investigate whether CSCR can be a precursor to PCV. In this review, we highlighted the currently available evidence on the pathogenesis, diagnosis, multimodality imaging features, and management strategies, including recent findings related to CSCR.
  9. Multiplex real-time pcr detection of respiratory viruses in lower respiratory tract infections in children
    Zetti Zainol Rashid, Umi Kalsom Ali, Muttaqillah Najihan Abdul Samat, Pei CL, Swee FT
    Sains Malaysiana, 2018;47:2821-2829.
    Acute respiratory infections cause significant morbidity and mortality in children. Several new respiratory viruses have
    been identified and co-detection of multiple viruses is commonly reported. This is part of a prospective study which
    aims to detect respiratory viruses by multiplex molecular method and conventional methods. Nasopharyngeal aspirate
    specimens were taken from hospitalised children aged less than 5 years with lower respiratory tract infections. These
    were tested using viral culture, immunofluorescence and Seegene Anyplex™ II RV16 real-time polymerase chain reaction.
    From 102 samples, 69 (67.6%) were positive by PCR, 12 (11.8%) positive by culture method and 13 (12.7%) positive
    by IF. A single viral pathogen was detected in 48 samples (47.1%), while 21 samples (20.6%) had co-detection of 2 to
    4 viral pathogens. Respiratory syncytial virus (RSV) was most common, detected in 17 samples (16.7% of all samples),
    followed by adenovirus and rhinovirus in 16 (15.7%), respectively. Bocavirus was detected in 15, enterovirus in 15,
    influenza A in 8 and parainfluenza-4 in 4 samples, with highest occurrences in co-detection (12/15, 10/15, 5/8 and 3/4,
    respectively). RSV was the least likely detected in co-detection (3/17). In PCR-positive samples, 54/69 (78.3%) were patients
    aged up to 24 months. Molecular methods detect more viral aetiologies than conventional methods, with simultaneous
    detection of multiple respiratory viruses. More sensitive, specific and rapid tools to determine aetiological agents could
    be incorporated into diagnostic algorithms of respiratory tract infections. Interpretations, significance, and applicability
    in clinical practice could be further explored, particularly for patients up to 2 years old.
  10. Fulltext Effectiveness of antismoking media messages and education among adolescents in Malaysia and Thailand: findings from the international tobacco control southeast Asia project
    Zawahir S, Omar M, Awang R, Yong HH, Borland R, Sirirassamee B, et al.
    Nicotine Tob Res, 2013 Feb;15(2):482-91.
    PMID: 22949569 DOI: 10.1093/ntr/nts161
    Finding ways to discourage adolescents from taking up smoking is important because those who begin smoking at an earlier age are more likely to become addicted and have greater difficulty in quitting. This article examined whether anti smoking messages and education could help to reduce smoking susceptibility among adolescents in two Southeast Asian countries and to explore the possible moderating effect of country and gender.
  11. Fulltext Flavone enhances dengue virus type-2 (NGC strain) infectivity and replication in vero cells
    Zandi K, Lani R, Wong PF, Teoh BT, Sam SS, Johari J, et al.
    Molecules, 2012;17(3):2437-45.
    PMID: 22374315 DOI: 10.3390/molecules17032437
    This study investigates the effects of 2-phenyl-1-benzopyran-4-one (flavone) on DENV-2 infectivity in Vero cells. Virus adsorption and attachment and intracellular virus replication were investigated using a foci forming unit assay (FFUA) and quantitative RT-PCR, respectively. Addition of flavone (100 μg/mL) significantly increased the number of DENV-2 foci by 35.66% ± 1.52 and 49.66% ± 2.51 when added during and after virus adsorption to the Vero cells, respectively. The average foci size after 4 days of infection increased by 33% ± 2.11 and 89% ± 2.13. The DENV-2 specific RNA copy number in the flavone-treated infected cells increased by 6.41- and 23.1-fold when compared to the mock-treated infected cells. Flavone (100 μg/mL) did not promote or inhibit Vero cell proliferation. The CC₅₀ value of flavone against Vero cells was 446 µg/mL. These results suggest that flavone might enhance dengue virus replication by acting antagonistically towards flavonoids known to inhibit dengue virus replication.
  12. Fulltext Novel antiviral activity of baicalein against dengue virus
    Zandi K, Teoh BT, Sam SS, Wong PF, Mustafa MR, Abubakar S
    BMC Complement Altern Med, 2012;12:214.
    PMID: 23140177 DOI: 10.1186/1472-6882-12-214
    Dengue is a serious arboviral disease currently with no effective antiviral therapy or approved vaccine available. Therefore, finding the effective compound against dengue virus (DENV) replication is very important. Among the natural compounds, bioflavonoids derived mainly from plants are of interest because of their biological and medicinal benefits.
  13. Fulltext Antiviral activity of four types of bioflavonoid against dengue virus type-2
    Zandi K, Teoh BT, Sam SS, Wong PF, Mustafa MR, Abubakar S
    Virol J, 2011;8:560.
    PMID: 22201648 DOI: 10.1186/1743-422X-8-560
    Dengue is a major mosquito-borne disease currently with no effective antiviral or vaccine available. Effort to find antivirals for it has focused on bioflavonoids, a plant-derived polyphenolic compounds with many potential health benefits. In the present study, antiviral activity of four types of bioflavonoid against dengue virus type -2 (DENV-2) in Vero cell was evaluated. Anti-dengue activity of these compounds was determined at different stages of DENV-2 infection and replication cycle. DENV replication was measured by Foci Forming Unit Reduction Assay (FFURA) and quantitative RT-PCR. Selectivity Index value (SI) was determined as the ratio of cytotoxic concentration 50 (CC50) to inhibitory concentration 50 (IC50) for each compound.
  14. Fulltext The puberty profile of female adolescents in Cheras, Malaysia
    Zainuddin, A.A., Anizah, A., Fong, A.H., Nur Azurah, A.G., Aiman, H., Siti Nazirah, M.S., et al.
    JUMMEC, 2018;21(2):64-69.
    MyJurnal
    Objectives: The objectives of our study were to determine the mean age of onset of thelarche and menarche,
    to determine the ages of each stage of puberty and to investigate if there are any ethnic differences in these
    ages amongst female adolescents in Kuala Lumpur, Malaysia.
    Methods: This was a cross-sectional study involving three secondary schools in Cheras, Kuala Lumpur. A total of
    730 students were recruited via stratified random sampling. Self-administered survey forms on menstruation
    and puberty were used.
    Results: Out of 730 recruited respondents, 385 (52.74%) completed the survey and informed consents were
    obtained from their parents/legal guardians. Our respondents’ ages ranged between 13 to 17 years old with
    the median (IQR) age of 14.00(2.00) years. With regards to ethnicity, 329 (85.50%) were Malay, 46 (11.90%)
    were Chinese, 9 (2.30%) were Indian and 1(0.30%) was a Bajau. The mean age for breast development
    (thelarche) and menarche were 11.72 ±1.10 and 11.97±1.11 years respectively. The majority, 363 (94.30%),
    out of 385 respondents had attained menarche. There appeared to be a later onset of puberty amongst
    Malays comparatively.
    Conclusion: The mean ages of pubertal onset and menarche amongst female adolescents in the Cheras area
    are similar to those reported worldwide.
  15. Streptomyces humi sp. nov., an actinobacterium isolated from soil of a mangrove forest
    Zainal N, Ser HL, Yin WF, Tee KK, Lee LH, Chan KG
    Antonie Van Leeuwenhoek, 2016 Mar;109(3):467-74.
    PMID: 26786500 DOI: 10.1007/s10482-016-0653-1
    A novel Streptomyces strain, MUSC 119(T), was isolated from a soil collected from a mangrove forest. Cells of MUSC 119(T) stained Gram-positive and formed light brownish grey aerial mycelium and grayish yellowish brown substrate mycelium on ISP 2 medium. A polyphasic approach was used to determine the taxonomic status of strain MUSC 119(T), which shows a range of phylogenetic and chemotaxonomic properties consistent with those of the genus Streptomyces. The cell wall peptidoglycan consisted of LL-diaminopimelic acid. The predominant menaquinones were identified as MK-9(H8), MK-9(H6) and MK-9(H4). The polar lipid profile consisted of phosphatidylinositol, phosphatidylethanolamine, glycolipids, diphosphatidylglycerol and four phospholipids. The predominant cellular fatty acids were anteiso-C15:0, iso-C16:0, and anteiso-C17:0. The cell wall sugars were glucose, mannose, ribose and rhamnose. The phylogenetic analysis based on 16S rRNA gene sequence similarity showed that strain MUSC119(T) to be closely related to Streptomyces rhizophilus JR-41(T) (99.0 % sequence similarity), S. panaciradicis 1MR-8(T) (98.9 %), S. gramineus JR-43(T) (98.8 %) and S. graminisoli JR-19(T) (98.7 %). These results suggest that MUSC 119(T) should be placed within the genus Streptomyces. DNA-DNA relatedness values between MUSC 119(T) to closely related strains ranged from 14.5 ± 1.3 to 27.5 ± 0.7 %. The G+C content was determined to be 72.6 mol  %. The polyphasic study of MUSC 119(T) showed that this strain represents a novel species, for which the name Streptomyces humi sp. nov. is proposed. The type strain of S. humi is MUSC 119(T) (=DSM 42174(T) = MCCC 1K00505(T)).
  16. Fulltext Circulating miRNAs in Type 2 Diabetic Patients with and without Albuminuria in Malaysia
    Zahari Sham SY, Ng CT, Azwar S, Yip WK, Abdullah M, Thevandran K, et al.
    Kidney Blood Press Res, 2022;47(2):81-93.
    PMID: 35158353 DOI: 10.1159/000518866
    INTRODUCTION: Diabetic kidney disease (DKD) remains the leading cause of chronic kidney disease. Dysregulation of circulating miRNAs has been reported, suggesting their pathological roles in DKD. This study aimed to investigate differentially expressed miRNAs in the sera of type 2 diabetes mellitus (T2DM) patients with and without albuminuria in a selected Malaysian population.

    METHOD: Forty-one T2DM patients on follow-up at a community clinic were divided into normo-(NA), micro-(MIC), and macroalbuminuria (MAC) groups. Differential levels of miRNAs in 12 samples were determined using the pathway-focused (human fibrosis) miScript miRNA qPCR array and was validated in 33 samples, using the miScript custom qPCR array (CMIHS02742) (Qiagen GmbH, Hilden, Germany).

    RESULTS: Trends of upregulation of 3 miRNAs in the serum, namely, miR-874-3p, miR-101-3p, and miR-145-5p of T2DM patients with MAC compared to those with NA. Statistically significant upregulation of miR-874-3p (p = 0.04) and miR-101-3p (p = 0.01) was seen in validation cohort. Significant negative correlations between the estimated glomerular filtration rate (eGFR) and miR-874-3p (p = 0.05), miR-101-3p (p = 0.03), and miR-145-5p (p = 0.05) as well as positive correlation between miR-874-3p and age (p = 0.03) were shown by Pearson's correlation coefficient analysis.

    CONCLUSION: Upregulation of previously known miRNA, namely, miR-145-5p, and possibly novel ones, namely, miR-874-3p and miR-101-3p in the serum of T2DM patients, was found in this study. There was a significant correlation between the eGFR and these miRNAs. The findings of this study have provided encouraging evidence to further investigate the putative roles of these differentially expressed miRNAs in DKD.

  17. Fulltext High proportion of knowlesi malaria in recent malaria cases in Malaysia
    Yusof R, Lau YL, Mahmud R, Fong MY, Jelip J, Ngian HU, et al.
    Malar J, 2014;13:168.
    PMID: 24886266 DOI: 10.1186/1475-2875-13-168
    Plasmodium knowlesi is a simian parasite that has been recognized as the fifth species causing human malaria. Naturally-acquired P. knowlesi infection is widespread among human populations in Southeast Asia. The aim of this epidemiological study was to determine the incidence and distribution of malaria parasites, with a particular focus on human P. knowlesi infection in Malaysia.
  18. Fulltext Phylogeographic Evidence for 2 Genetically Distinct Zoonotic Plasmodium knowlesi Parasites, Malaysia
    Yusof R, Ahmed MA, Jelip J, Ngian HU, Mustakim S, Hussin HM, et al.
    Emerg Infect Dis, 2016 Aug;22(8):1371-80.
    PMID: 27433965 DOI: 10.3201/eid2208.151885
    Infections of humans with the zoonotic simian malaria parasite Plasmodium knowlesi occur throughout Southeast Asia, although most cases have occurred in Malaysia, where P. knowlesi is now the dominant malaria species. This apparently skewed distribution prompted an investigation of the phylogeography of this parasite in 2 geographically separated regions of Malaysia, Peninsular Malaysia and Malaysian Borneo. We investigated samples collected from humans and macaques in these regions. Haplotype network analyses of sequences from 2 P. knowlesi genes, type A small subunit ribosomal 18S RNA and cytochrome c oxidase subunit I, showed 2 genetically distinct divergent clusters, 1 from each of the 2 regions of Malaysia. We propose that these parasites represent 2 distinct P. knowlesi types that independently became zoonotic. These types would have evolved after the sea-level rise at the end of the last ice age, which separated Malaysian Borneo from Peninsular Malaysia.
  19. Fulltext Pseudomonas cremoricolorata strain ND07 produces N-acyl homoserine lactones as quorum sensing molecules
    Yunos NY, Tan WS, Koh CL, Sam CK, Mohamad NI, Tan PW, et al.
    Sensors (Basel), 2014;14(7):11595-604.
    PMID: 24984061 DOI: 10.3390/s140711595
    Quorum sensing (QS) is a bacterial cell-to-cell communication system controlling QS-mediated genes which is synchronized with the population density. The regulation of specific gene activity is dependent on the signaling molecules produced, namely N-acyl homoserine lactones (AHLs). We report here the identification and characterization of AHLs produced by bacterial strain ND07 isolated from a Malaysian fresh water sample. Molecular identification showed that strain ND07 is clustered closely to Pseudomonas cremoricolorata. Spent culture supernatant extract of P. cremoricolorata strain ND07 activated the AHL biosensor Chromobacterium violaceum CV026. Using high resolution triple quadrupole liquid chromatography-mass spectrometry, it was confirmed that P. cremoricolorata strain ND07 produced N-octanoyl-L-homoserine lactone (C8-HSL) and N-decanoyl-L-homoserine lactone (C10-HSL). To the best of our knowledge, this is the first documentation on the production of C10-HSL in P. cremoricolorata strain ND07.
  20. Fulltext Discovery of Pantoea rodasii strain ND03 that produces N-(3-Oxo-hexanoyl)-L-homoserine lactone
    Yunos NY, Tan WS, Mohamad NI, Tan PW, Adrian TG, Yin WF, et al.
    Sensors (Basel), 2014;14(5):9145-52.
    PMID: 24859023 DOI: 10.3390/s140509145
    Proteobacteria use quorum sensing to regulate target gene expression in response to population density. Quorum sensing (QS) is achieved via so-called signalling molecules and the best-studied QS signalling system uses N-acyl homoserine lactones (AHLs). This study aimed to identify and characterize the production of AHLs by a bacterium ND03 isolated from a Malaysian tropical rainforest waterfall. Molecular identification showed that ND03 is a Pantoea sp. closely related to Pantoea rodasii. We used Chromobacterium violaceum CV026, an AHL biosensor for preliminary AHL production screening and then used high resolution triple quadrupole liquid chromatography-mass spectrometry, to confirm that P. rodasii strain ND03 produced N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL). To the best of our knowledge, this is the first report for such a discovery in P. rodasii strain ND03.
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