National Environmental Agency

Adjara, Georgia

National Environmental Agency

Adjara, Georgia
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Yung C.-F.,Tan Tock Seng Hospital | Lee K.-S.,National Environmental Agency | Thein T.-L.,Tan Tock Seng Hospital | Tan L.-K.,National Environmental Agency | And 7 more authors.
American Journal of Tropical Medicine and Hygiene | Year: 2015

Studies on serotype-specific features of dengue and disease severity on adults are limited. We prospectively recruited adult febrile patients without alternate diagnosis to dengue from April 2005 to December 2011. Outcomes were defined using both the World Health Organization (WHO) 1997 and 2009 criteria; Dengue hemorrhagic fever (DHF) and severe dengue (SD). Infecting serotype was identified in 469 dengue-confirmed patients comprising 22.0% dengue virus serotype 1 (DENV-1), 57.1% DENV-2, 17.1% DENV-3, and 3.8% DENV-4. Cases infected with DENV-1 were more likely to present with red eyes whereas presence of joint pain and lower platelet count was associated with DENV-2 cases. After adjusting for potential confounders, DENV-1 was associated with both DHF (adjusted Relative Risk [aRR] = 1.74) and SD (aRR = 2.1) whereas DENV-2 had a lower risk of DHF (aRR = 0.5). DENV-1 genotype 1 and DENV-2 cosmopolitan were the predominant genotypes identified. Infecting dengue serotype and possibly genotype may play an important role in disease severity among adult dengue patients in Singapore. Copyright © 2015 by The American Society of Tropical Medicine and Hygiene.


Kam Y.-W.,Agency for Science, Technology and Research Singapore | Pok K.-Y.,National Environmental Agency | Eng K.E.,Agency for Science, Technology and Research Singapore | Tan L.-K.,National Environmental Agency | And 7 more authors.
PLoS Neglected Tropical Diseases | Year: 2015

Chikungunya virus (CHIKV) and clinically-related arboviruses cause large epidemics with serious economic and social impact. As clinical symptoms of CHIKV infections are similar to several flavivirus infections, good detection methods to identify CHIKV infection are desired for improved treatment and clinical management. The strength of anti-E2EP3 antibody responses was explored in a longitudinal study on 38 CHIKV-infected patients. We compared their anti-E2EP3 responses with those of patients infected with non-CHIKV alphaviruses, or flaviviruses. E2EP3 cross-reactive samples from patients infected with non-CHIKV viruses were further analyzed with an in vitro CHIKV neutralization assay. CHIKV-specific anti-E2EP3 antibody responses were detected in 72% to 100% of patients. Serum samples from patients infected with other non-CHIKV alphaviruses were cross-reactive to E2EP3. Interestingly, some of these antibodies demonstrated clearly in vitro CHIKV neutralizing activity. Contrastingly, serum samples from flaviviruses-infected patients showed a low level of cross-reactivity against E2EP3. Using CHIKV E2EP3 as a serology marker not only allows early detection of CHIKV specific antibodies, but would also allow the differentiation between CHIKV infections and flavivirus infections with 93% accuracy, thereby allowing precise acute febrile diagnosis and improving clinical management in regions newly suffering from CHIKV outbreaks including the Americas. © 2015 Kam et al.


Lee R.C.H.,National University of Singapore | Hapuarachchi H.C.,National Environmental Agency | Chen K.C.,National University of Singapore | Hussain K.,National University of Singapore | And 6 more authors.
PLoS Neglected Tropical Diseases | Year: 2013

Chikungunya virus (CHIKV) is an arthropod-borne virus responsible for recent epidemics in the Asia Pacific regions. A customized gene expression microarray of 18,760 transcripts known to target Aedes mosquito genome was used to identify host genes that are differentially regulated during the infectious entry process of CHIKV infection on C6/36 mosquito cells. Several genes such as epsin I (EPN1), epidermal growth factor receptor pathway substrate 15 (EPS15) and Huntingtin interacting protein I (HIP1) were identified to be differentially expressed during CHIKV infection and known to be involved in clathrin-mediated endocytosis (CME). Transmission electron microscopy analyses further revealed the presence of CHIKV particles within invaginations of the plasma membrane, resembling clathrin-coated pits. Characterization of vesicles involved in the endocytic trafficking processes of CHIKV revealed the translocation of the virus particles to the early endosomes and subsequently to the late endosomes and lysosomes. Treatment with receptor-mediated endocytosis inhibitor, monodansylcadaverine and clathrin-associated drug inhibitors, chlorpromazine and dynasore inhibited CHIKV entry, whereas no inhibition was observed with caveolin-related drug inhibitors. Inhibition of CHIKV entry upon treatment with low-endosomal pH inhibitors indicated that low pH is essential for viral entry processes. CHIKV entry by clathrin-mediated endocytosis was validated via overexpression of a dominant-negative mutant of Eps15, in which infectious entry was reduced, while siRNA-based knockdown of genes associated with CME, low endosomal pH and RAB trafficking proteins exhibited significant levels of CHIKV inhibition. This study revealed, for the first time, that the infectious entry of CHIKV into mosquito cells is mediated by the clathrin-dependent endocytic pathway. © 2013 Lee et al.


Rai V.,Nanyang Technological University | Hapuarachchi H.C.,National Environmental Agency | Ng L.C.,National Environmental Agency | Soh S.H.,Tan Tock Seng Hospital | And 2 more authors.
PLoS ONE | Year: 2012

A nanoporous alumina membrane-based ultrasensitive DNA biosensor is constructed using 5′-aminated DNA probes immobilized onto the alumina channel walls. Alumina nanoporous membrane-like structure is carved over platinum wire electrode of 76 μm diameter dimension by electrochemical anodization. The hybridization of complementary target DNA with probe DNA molecules attached inside the pores influences the pore size and ionic conductivity. The biosensor demonstrates linear range over 6 order of magnitude with ultrasensitive detection limit of 9.55×10-12 M for the quantification of ss-31 mer DNA sequence. Its applicability is challenged against real time cDNA PCR sample of dengue virus serotype1 derived from asymmetric PCR. Excellent specificity down to one nucleotide mismatch in target DNA sample of DENV3 is also demonstrated. © 2012 Rai et al.


Gaprindashvili G.,National Environmental Agency | Gaprindashvili G.,Tbilisi State University | Van Westen C.J.,University of Twente
Natural Hazards | Year: 2016

Landslide risk assessment for large areas at a country level requires a different approach and data than what is standard practice at large scales. The main goal of this research was to design a methodology for a nationwide landslide risk assessment for Georgia taking into account the limitations in data availability and detail, which do not allow the use of physically based models or statistical methods. Given these limitations, we decided to generate a qualitative landslide risk index using spatial multicriteria evaluation (SMCE). An attempt was made to compile a national landslide inventory, using old and partly destroyed archives from the Soviet period, combined with information from annual field surveys. A web-based interface for the reporting of landslide events was developed to improve the updating of the inventory in future. Relevant factor maps were prepared for the entire country, partly based on remote sensing data. As the available landslide inventory was not sufficient to use statistical methods, the factor maps were weighted using the expert-based SMCE method, and the resulting susceptibility map was validated using the available landslide inventory. The inventory was also used to make an estimation of the spatial probability of landslide occurrence within the various susceptibility classes. The resulting map was used in combination with element-at-risk maps to calculate exposure maps and to make a tentative assessment of the expected landslide losses in a 50-year time period. © 2015, Springer Science+Business Media Dordrecht.


Cheng M.S.,Nanyang Technological University | Ho J.S.,Nanyang Technological University | Tan C.H.,National Environmental Agency | Wong J.P.S.,National Environmental Agency | And 2 more authors.
Analytica Chimica Acta | Year: 2012

A sensitive membrane-based electrochemical nanobiosensor is developed for the detection of dengue type 2 virus (DENV-2) using nanoporous alumina-modified platinum electrode. Its sensing mechanism relies on the monitoring of electrode's Faradaic current response toward redox probe, ferrocenemethanol, which is sensitive toward the formation of immune complexes within the alumina nanochannels. Anti-DENV-2 monoclonal antibody (clone 3H5, isotype IgG) is used as the biorecognition element in this work. The stepwise additions of antibody, bovine serum albumin (BSA) and DENV-2 are characterized by differential pulse voltammetry (DPV). A low detection limit of 1pfumL -1 with linear range from 1 to 10 3pfumL -1 (R 2=0.98) can be achieved by the nanobiosensor. The nanobiosensor is selective toward DENV-2 with insignificant cross reaction with non-specific viruses, Chikungunya virus, West Nile virus and dengue type 3 virus (DENV-3). Relative standard deviation (RSD) for triplicate analysis of 5.9% indicates an acceptable level of reproducibility. The first direct quantitation of DENV-2 concentration in whole mosquito vector is demonstrated using this electrochemical nanobiosensor. © 2012 Elsevier B.V.


Kasai S.,Japan National Institute of Infectious Diseases | Ng L.C.,National Environmental Agency | Lam-Phua S.G.,National Environmental Agency | Tang C.S.,National Environmental Agency | And 4 more authors.
Japanese Journal of Infectious Diseases | Year: 2011

SUMMARY: The Asian tiger mosquito, Aedes albopictus (Skuse), is the major vector of Chikungunya fever and the secondary vector of dengue fever. We collected Ae. albopictus from Singapore and performed genotyping assay to detect mutations of the voltage-gated sodium channel, which is the target site of pyrethroid insecticides. We detected an amino acid substitution, F1534C, which is suspected to confer knockdown resistance (kdr) to pyrethroid insecticides. Of the collected mosquitoes, 53.8z were homozygous for this mutation, and the allele frequency of this mutation was estimated to be 73.1z. No kdr mutation was detected in the 5 other loci of domains II and IV. This is the first evidence for the presence of the kdr gene in Ae. albopictus, and our findings highlight the need for studying the global distribution of this allele in this important vector insect.


Kasai S.,Japan National Institute of Infectious Diseases | Komagata O.,Japan National Institute of Infectious Diseases | Itokawa K.,Japan National Institute of Infectious Diseases | Shono T.,Japan National Institute of Infectious Diseases | And 3 more authors.
PLoS Neglected Tropical Diseases | Year: 2014

Aedes aegypti is the major vector of yellow and dengue fevers. After 10 generations of adult selection, an A. aegypti strain (SP) developed 1650-fold resistance to permethrin, which is one of the most widely used pyrethroid insecticides for mosquito control. SP larvae also developed 8790-fold resistance following selection of the adults. Prior to the selections, the frequencies of V1016G and F1534C mutations in domains II and III, respectively, of voltage-sensitive sodium channel (Vssc, the target site of pyrethroid insecticide) were 0.44 and 0.56, respectively. In contrast, only G1016 alleles were present after two permethrin selections, indicating that G1016 can more contribute to the insensitivity of Vssc than C1534. In vivo metabolism studies showed that the SP strain excreted permethrin metabolites more rapidly than a susceptible SMK strain. Pretreatment with piperonyl butoxide caused strong inhibition of excretion of permethrin metabolites, suggesting that cytochrome P450 monooxygenases (P450s) play an important role in resistance development. In vitro metabolism studies also indicated an association of P450s with resistance. Microarray analysis showed that multiple P450 genes were over expressed during the larval and adult stages in the SP strain. Following quantitative real time PCR, we focused on two P450 isoforms, CYP9M6 and CYP6BB2. Transcription levels of these P450s were well correlated with the rate of permethrin excretion and they were certainly capable of detoxifying permethrin to 4′-HO-permethrin. Over expression of CYP9M6 was partially due to gene amplification. There was no significant difference in the rate of permethrin reduction from cuticle between SP and SMK strains. © 2014 Kasai et al.


Gogichaishvili G.P.,National Environmental Agency
Eurasian Soil Science | Year: 2012

The erodibility of arable soils in Georgia varies from 1. 0 to 2. 9 t/ha per unit of the rainfall erosivity index. The well-structured brown forest and yellow-brown soils with a high humus content are the most resistant to erosion. The soils in the dry areas of Georgia (gray-cinnamon and cinnamon soils) are the most susceptible to erosion. The first map of the soil erodibility was composed that illustrates the spatial distribution pattern of this parameter in the Georgia territory. © 2012 Pleiades Publishing, Ltd.


Rai V.,Nanyang Technological University | Nyine Y.T.,Nanyang Technological University | Hapuarachchi H.C.,National Environmental Agency | Yap H.M.,National Environmental Agency | And 2 more authors.
Biosensors and Bioelectronics | Year: 2012

An electrochemically amplified molecular beacon (EAMB) biosensor is constructed using thiolated hairpin DNA-ferrocene probes on gold electrode. The switching from " on" to " off" states of individual probes in the presence of complementary DNA target influences the electrode potential, besides the current, owing to changes in surface density of the electroactive hairpin DNA-ferrocene probes. The EAMB biosensor demonstrates linear range over 8 orders of magnitude with ultrasensitive detection limit of 2.3×10 -14M for the quantification of a 21-mer DNA sequence. Its applicability is tested against PCR amplicons derived from genomic DNA of live Legionella pneumophila. Excellent specificity down to one and three nucleotides mismatches in another strain of L. pneumophila and a different bacterium species, respectively, is demonstrated. © 2011 Elsevier B.V.

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