19 results on '"Man Suen Chan"'
Search Results
2. Haplotype homozygosity and derived alleles in the human genome
- Author
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Fry, Andrew E., Trafford, Clare J., Kimber, Martin A., Man-Suen Chan, Rockett, Kirk A., and Kwiatkowski, Dominic P.
- Subjects
Human genome -- Research ,Haplotypes -- Research ,Single nucleotide polymorphisms -- Research ,Biological sciences - Abstract
A simple pairwise metric of haplotype homozygosity is shown to give significantly higher mean values for human single-nucleotide-polymorphism alleles that appear to be derived than for those that appear to be ancestral, as determined by comparison with the chimpanzee genome. Results support the use of haplotype-based techniques, such as extended haplotypic homozygosity, to assess the age of alleles.
- Published
- 2006
3. Identification of common genetic variation that modulates alternative splicing.
- Author
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Jeremy Hull, Susana Campino, Kate Rowlands, Man-Suen Chan, Richard R Copley, Martin S Taylor, Kirk Rockett, Gareth Elvidge, Brendan Keating, Julian Knight, and Dominic Kwiatkowski
- Subjects
Genetics ,QH426-470 - Abstract
Alternative splicing of genes is an efficient means of generating variation in protein function. Several disease states have been associated with rare genetic variants that affect splicing patterns. Conversely, splicing efficiency of some genes is known to vary between individuals without apparent ill effects. What is not clear is whether commonly observed phenotypic variation in splicing patterns, and hence potential variation in protein function, is to a significant extent determined by naturally occurring DNA sequence variation and in particular by single nucleotide polymorphisms (SNPs). In this study, we surveyed the splicing patterns of 250 exons in 22 individuals who had been previously genotyped by the International HapMap Project. We identified 70 simple cassette exon alternative splicing events in our experimental system; for six of these, we detected consistent differences in splicing pattern between individuals, with a highly significant association between splice phenotype and neighbouring SNPs. Remarkably, for five out of six of these events, the strongest correlation was found with the SNP closest to the intron-exon boundary, although the distance between these SNPs and the intron-exon boundary ranged from 2 bp to greater than 1,000 bp. Two of these SNPs were further investigated using a minigene splicing system, and in each case the SNPs were found to exert cis-acting effects on exon splicing efficiency in vitro. The functional consequences of these SNPs could not be predicted using bioinformatic algorithms. Our findings suggest that phenotypic variation in splicing patterns is determined by the presence of SNPs within flanking introns or exons. Effects on splicing may represent an important mechanism by which SNPs influence gene function.
- Published
- 2007
- Full Text
- View/download PDF
4. Sequence type analysis and recombinational tests (START).
- Author
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Keith A. Jolley, E. J. Feil, Man-Suen Chan, and Martin C. J. Maiden
- Published
- 2001
- Full Text
- View/download PDF
5. mlstdbNet - distributed multi-locus sequence typing (MLST) databases.
- Author
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Keith A. Jolley, Man-Suen Chan, and Martin C. J. Maiden
- Published
- 2004
- Full Text
- View/download PDF
6. Identification of common genetic variation that modulates alternative splicing
- Author
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Julian C. Knight, Martin S. Taylor, Dominic P. Kwiatkowski, Kate Rowlands, Jeremy Hull, Man-Suen Chan, Richard R. Copley, Susana Campino, Gareth Elvidge, Kirk A. Rockett, and Brendan J. Keating
- Subjects
Cancer Research ,lcsh:QH426-470 ,Single-nucleotide polymorphism ,Biology ,Polymorphism, Single Nucleotide ,Cell Line ,03 medical and health sciences ,Exon ,0302 clinical medicine ,Homo (Human) ,Genetic variation ,Genetics ,Humans ,Protein Isoforms ,Molecular Biology ,Gene ,Genetics (clinical) ,Ecology, Evolution, Behavior and Systematics ,030304 developmental biology ,0303 health sciences ,Alternative splicing ,Intron ,Genetic Variation ,Genetics and Genomics ,Exons ,lcsh:Genetics ,Alternative Splicing ,030220 oncology & carcinogenesis ,RNA splicing ,RNA Splice Sites ,Minigene ,Research Article - Abstract
Alternative splicing of genes is an efficient means of generating variation in protein function. Several disease states have been associated with rare genetic variants that affect splicing patterns. Conversely, splicing efficiency of some genes is known to vary between individuals without apparent ill effects. What is not clear is whether commonly observed phenotypic variation in splicing patterns, and hence potential variation in protein function, is to a significant extent determined by naturally occurring DNA sequence variation and in particular by single nucleotide polymorphisms (SNPs). In this study, we surveyed the splicing patterns of 250 exons in 22 individuals who had been previously genotyped by the International HapMap Project. We identified 70 simple cassette exon alternative splicing events in our experimental system; for six of these, we detected consistent differences in splicing pattern between individuals, with a highly significant association between splice phenotype and neighbouring SNPs. Remarkably, for five out of six of these events, the strongest correlation was found with the SNP closest to the intron–exon boundary, although the distance between these SNPs and the intron–exon boundary ranged from 2 bp to greater than 1,000 bp. Two of these SNPs were further investigated using a minigene splicing system, and in each case the SNPs were found to exert cis-acting effects on exon splicing efficiency in vitro. The functional consequences of these SNPs could not be predicted using bioinformatic algorithms. Our findings suggest that phenotypic variation in splicing patterns is determined by the presence of SNPs within flanking introns or exons. Effects on splicing may represent an important mechanism by which SNPs influence gene function., Author Summary Genetic variation, through its effects on gene expression, influences many aspects of the human phenotype. Understanding the impact of genetic variation on human disease risk has become a major goal for biomedical research and has the potential of revealing both novel disease mechanisms and novel functional elements controlling gene expression. Recent large-scale studies have suggested that a relatively high proportion of human genes show allele-specific variation in expression. Effects of common DNA polymorphisms on mRNA splicing are less well studied. Variation in splicing patterns is known to be tissue specific, and for a small number of genes has been shown to vary among individuals. What is not known is whether allele-specific splicing events are an important mechanism by which common genetic variation affects gene expression. In this study we show that allele-specific alternative splicing was observed in six out of 70 exon-skipping events. Sequence analysis of the relevant splice sites and of the regions surrounding single nucleotide polymorphisms correlated with the splicing events failed to identify any predictive bioinformatic signals. A genome-wide study of allele-specific splicing, using an experimental rather than a bioinformatic approach, is now required.
- Published
- 2016
7. Multilocus sequence typing system for group B streptococcus
- Author
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Christophe Rusniok, Nicola Jones, Naiel Bisharat, Brian G. Spratt, Man Suen Chan, Frank Kunst, John F. Bohnsack, Derrick W. Crook, Shinji Takahashi, Philippe Glaser, Karen A. Oliver, and Rosalind M. Harding
- Subjects
Microbiology (medical) ,Serotype ,Adult ,Sequence analysis ,Molecular Sequence Data ,Locus (genetics) ,Biology ,medicine.disease_cause ,Microbiology ,Streptococcus agalactiae ,Bacterial Proteins ,Streptococcal Infections ,Genotype ,medicine ,Humans ,Typing ,Alleles ,Genetics ,Molecular epidemiology ,Base Sequence ,Infant, Newborn ,Computational Biology ,Bacteriology ,Sequence Analysis, DNA ,bacterial infections and mycoses ,Bacterial Typing Techniques ,Multilocus sequence typing - Abstract
A multilocus sequence typing (MLST) system was developed for group B streptococcus (GBS). The system was used to characterize a collection ( n = 152) of globally and ecologically diverse human strains of GBS that included representatives of capsular serotypes Ia, Ib, II, III, V, VI, and VIII. Fragments (459 to 519 bp) of seven housekeeping genes were amplified by PCR for each strain and sequenced. The combination of alleles at the seven loci provided an allelic profile or sequence type (ST) for each strain. A subset of the strains were characterized by restriction digest patterning, and these results were highly congruent with those obtained with MLST. There were 29 STs, but 66% of isolates were assigned to four major STs. ST-1 and ST-19 were significantly associated with asymptomatic carriage, whereas ST-23 included both carried and invasive strains. All 44 isolates of ST-17 were serotype III clones, and this ST appeared to define a homogeneous clone that was strongly associated with neonatal invasive infections. The finding that isolates with different capsular serotypes had the same ST suggests that recombination occurs at the capsular locus. A web site for GBS MLST was set up and can be accessed at http://sagalactiae.mlst.net. The GBS MLST system offers investigators a valuable typing tool that will promote further investigation of the population biology of this organism.
- Published
- 2016
8. Genome sequence of the human malaria parasite Plasmodium falciparum
- Author
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Man Suen Chan, Alan H. Fairlamb, Jeremy D. Selengut, Leda M. Cummings, Arnab Pain, Vishvanath Nene, Martin Fraunholz, G. Mani Subramanian, Christopher J. Mungall, Akhil B. Vaidya, Bart Barrell, Jane M. Carlton, Jeremy Peterson, Chris I. Newbold, Richard W. Hyman, Daniel J. Carucci, Claire M. Fraser, Neil Hall, Matthew Berriman, Michael W. Mather, David S. Roos, Jonathan A. Eisen, Ronald W. Davis, Sue Kyes, Jonathan E. Allen, Eula Fung, Kim Rutherford, Geoffrey I. McFadden, Samuel V. Angiuoli, Karen E. Nelson, Owen White, J. Craig Venter, Alister Craig, Steven L. Salzberg, Shamira J. Shallom, Mihaela Pertea, David M. A. Martin, Stuart A. Ralph, Bernard B. Suh, Daniel H. Haft, Keith D. James, Ian T. Paulsen, Stephen L. Hoffman, Sharen Bowman, and Malcolm J. Gardner
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DNA Replication ,Genome evolution ,DNA Repair ,Proteome ,Molecular Sequence Data ,Plasmodium falciparum ,Protozoan Proteins ,Genomics ,Biology ,Genome ,Article ,Evolution, Molecular ,parasitic diseases ,Malaria Vaccines ,Animals ,Humans ,Plastids ,Malaria, Falciparum ,Gene ,Genetics ,Recombination, Genetic ,Pregnancy-associated malaria ,Apicoplast ,Multidisciplinary ,Membrane Transport Proteins ,Sequence Analysis, DNA ,DNA, Protozoan ,biology.organism_classification ,Chromosome Structures ,Genome, Protozoan - Abstract
The parasite Plasmodium falciparum is responsible for hundreds of millions of cases of malaria, and kills more than one million African children annually. Here we report an analysis of the genome sequence of P. falciparum clone 3D7. The 23-megabase nuclear genome consists of 14 chromosomes, encodes about 5,300 genes, and is the most (A + T)-rich genome sequenced to date. Genes involved in antigenic variation are concentrated in the subtelomeric regions of the chromosomes. Compared to the genomes of free-living eukaryotic microbes, the genome of this intracellular parasite encodes fewer enzymes and transporters, but a large proportion of genes are devoted to immune evasion and host-parasite interactions. Many nuclear-encoded proteins are targeted to the apicoplast, an organelle involved in fatty-acid and isoprenoid metabolism. The genome sequence provides the foundation for future studies of this organism, and is being exploited in the search for new drugs and vaccines to fight malaria.
- Published
- 2016
9. Recombination within natural populations of pathogenic bacteria: Short-term empirical estimates and long-term phylogenetic consequences
- Author
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Brian G. Spratt, Edward J. Feil, Mark C. Enright, Derek W. Hood, Edward C. Holmes, Richard Goldstein, Man Suen Chan, Jiaji Zhou, Catrin E. Moore, Awdhesh Kalia, Debra E. Bessen, and Nicholas P. J. Day
- Subjects
Genotype ,Molecular Sequence Data ,Statistics as Topic ,Biology ,medicine.disease_cause ,Bacterial genetics ,Phylogenetics ,Genetic variation ,medicine ,Point Mutation ,Gene ,Alleles ,Phylogeny ,Recombination, Genetic ,Genetics ,Multidisciplinary ,Bacteria ,Base Sequence ,Phylogenetic tree ,Neisseria meningitidis ,Genetic Variation ,Biological Sciences ,Kinetics ,Genes, Bacterial ,Mutagenesis ,Streptococcus pyogenes ,Transformation, Bacterial ,Recombination - Abstract
The identification of clones within bacterial populations is often taken as evidence for a low rate of recombination, but the validity of this inference is rarely examined. We have used statistical tests of congruence between gene trees to examine the extent and significance of recombination in six bacterial pathogens. For Neisseria meningitidis , Streptococcus pneumoniae , Streptococcus pyogenes, and Staphylococcus aureus , the congruence between the maximum likelihood trees reconstructed using seven house-keeping genes was in most cases no better than that between each tree and trees of random topology. The lack of congruence between gene trees in these four species, which include both naturally transformable and nontransformable species, is in three cases supported by high ratios of recombination to point mutation during clonal diversification (estimates of this parameter were not possible for Strep. pyogenes ). In contrast, gene trees constructed for Hemophilus influenzae and pathogenic isolates of Escherichia coli showed a higher degree of congruence, suggesting lower rates of recombination. The impact of recombination therefore varies between bacterial species but in many species is sufficient to obliterate the phylogenetic signal in gene trees.
- Published
- 2001
10. The Cost Effectiveness of Strategies for the Treatment of Intestinal Parasites in Immigrants
- Author
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Randall L. Sell, Man-Suen Chan, Daniel J. Pallin, and Peter A. Muennig
- Subjects
medicine.medical_specialty ,Cost effectiveness ,Cost-Benefit Analysis ,medicine.medical_treatment ,media_common.quotation_subject ,Immigration ,Albendazole ,Asymptomatic ,Drug Costs ,Decision Support Techniques ,Food and drug administration ,Feces ,Cost of Illness ,Environmental health ,Preventive Health Services ,Humans ,Mass Screening ,Medicine ,Intestinal Diseases, Parasitic ,health care economics and organizations ,media_common ,Public health ,business.industry ,General Medicine ,Emigration and Immigration ,Surgery ,Hospitalization ,Models, Economic ,Preventive intervention ,medicine.symptom ,business ,Watchful waiting ,medicine.drug - Abstract
Background: Currently, more than 600,000 immigrants enter the United States each year from countries where intestinal parasites are endemic. At entry persons with parasitic infections may be asymptomatic, and stool examinations are not a sensitive method of screening for parasitosis. Albendazole is a new, broad-spectrum antiparasitic drug, which was approved recently by the Food and Drug Administration. International trials have shown albendazole to be safe and effective in eradicating many parasites. In the United States there is now disagreement about whether to screen all immigrants for parasites, treat all immigrants presumptively, or do nothing unless they have symptoms. Methods: We compared the costs and benefits of no preventive intervention (watchful waiting) with those of universal screening or presumptive treatment with 400 mg of albendazole per day for five days. Those at risk were defined as immigrants to the United States from Asia, the Middle East, sub-Saharan Africa, Eastern Europe, and Latin America and the Caribbean. Cost effectiveness was expressed both in terms of the cost of treatment per disability adjusted life-year (DALY) averted (one DALY is defined as the loss of one year of healthy life to disease)and in terms of the cost per hospitalization averted. Results: As compared with watchful waiting, presumptive treatment of all immigrants at risk for parasitosis would avert at least 870 DALYs, prevent at least 33 deaths and 374 hospitalizations, and save at least $4.2 million per year. As compared with watchful waiting, screening would cost $159,236 per DALY averted. Conclusions: Presumptive administration of albendazole to all immigrants at risk for parasitosis would save lives and money. Universal screening, with treatment of persons with positive stool examinations, would save lives but is less cost effective than presumptive treatment.
- Published
- 1999
11. An investigation into the interaction between drug efficacy and drug price of praziquantel in determining the cost‐effectiveness of school‐targeted treatment for Schistosoma mansoni using a population dynamic model
- Author
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Man‐Suen Chan and Helen L. Guyatt
- Subjects
Male ,Drug ,Adolescent ,Cost effectiveness ,Cost-Benefit Analysis ,International Cooperation ,media_common.quotation_subject ,Population ,Helminthiasis ,Drug resistance ,Pharmacology ,Global Health ,Praziquantel ,Efficacy ,Antiplatyhelmintic Agents ,Environmental health ,parasitic diseases ,Prevalence ,Animals ,Humans ,Medicine ,Child ,education ,health care economics and organizations ,media_common ,education.field_of_study ,business.industry ,Public Health, Environmental and Occupational Health ,Cost-effectiveness analysis ,medicine.disease ,Schistosomiasis mansoni ,United Kingdom ,Treatment Outcome ,Infectious Diseases ,Female ,Parasitology ,business ,medicine.drug - Abstract
Summary SummaryA population dynamic model of schistosome transmission was used to investigate the interaction between drug efficacy and drug price of different brands of praziquantel in determining the cost-effectiveness of school-targeted treatment for Schistosoma mansoni. In this analysis, costs were affected by coverage, drug price and distance travelled, and effectiveness by coverage and drug efficacy. Four effectiveness measures were assessed: the number of infection case-years prevented, heavy infection case-years prevented, hepatomegaly case-years prevented and fibrosis case-years prevented. The interactions between drug efficacy and drug price were complex. In particular, there was a highly nonlinear relationship between drug efficacy and cost-effectiveness, with drugs of low efficacy producing high and variable cost-effectiveness ratios, particularly when other programme costs related to distance travelled were high. The results suggest that given the current price range of praziquantel, a drug with less than a 50% chance of killing the worms is not to be recommended. This has important practical implications for the widespread use of praziquantel, since most international agencies procure praziquantel purely on the basis of price. There is clearly a need for studies which evaluate the efficacy of new brands of praziquantel, and more credence should be given to the use of high efficacy brands, not only in terms of maximizing the cost-effectiveness of the intervention programme, but also in delaying the onset of drug resistance.
- Published
- 1998
12. Sequence type analysis and recombinational tests (START)
- Author
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Martin C. J. Maiden, Man-Suen Chan, Keith A. Jolley, and Edward J. Feil
- Subjects
Recombination, Genetic ,Statistics and Probability ,Genetics ,Lineage (genetic) ,Nucleic acid sequence ,Computational biology ,Biology ,Biochemistry ,Computer Science Applications ,Housekeeping gene ,Computational Mathematics ,Computational Theory and Mathematics ,DNA profiling ,Genes, Bacterial ,Multilocus sequence typing ,Typing ,Databases, Nucleic Acid ,Sequence Analysis ,Molecular Biology ,Software ,Selection (genetic algorithm) ,Sequence (medicine) - Abstract
Summary: The 32-bit Windows application START is implemented using Visual Basic and C ++ and performs analyses to aid in the investigation of bacterial population structure using multilocus sequence data. These analyses include data summary, lineage assignment, and tests for recombination and selection. Availability: START is available at http://outbreak.ceid.ox. ac.uk/software.htm. Contact: keith.jolley@ceid.ox.ac.uk Multilocus Sequence Typing (MLST) is a nucleotide sequence-based typing method that indexes the variation present in bacterial housekeeping genes, where most of the variation is selectively neutral (Maiden et al., 1998). Internal fragments of seven housekeeping genes, approximately 450–500 bp in length, are sequenced and novel alleles are assigned with arbitrary numbers sequentially to provide an allelic profile of seven integers that defines the Sequence Type (ST) of each isolate. The technique is designed primarily for global or long-term epidemiology and surveillance, and has the advantage over other typing methods, such as genetic fingerprinting, of electronic portability and unambiguous characterization of isolates. MLST schemes have been developed for a range of bacterial pathogens and databases for these organisms can be interrogated at the MLST web-site (http://www.mlst.net/) thus facilitating rapid comparisons of isolates typed using the method. A further advantage of MLST is that it provides large quantities of data that may be analyzed by a number of evolutionary approaches to yield insights into the structure of bacterial populations and the selective pressures which act upon them. With the increasing availability of MLST data, the need for software to describe and analyze datasets has become apparent. Sequence Type Analysis and Recombinational Tests (START) was written to address this need through the inclusion of multiple analytical techniques in an easyto-use and intuitive interface for Windows 95/98/NT/2000 operating systems.
- Published
- 2001
13. [Untitled]
- Author
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Keith A. Jolley, Martin C. J. Maiden, and Man Suen Chan
- Subjects
0303 health sciences ,Database ,030306 microbiology ,computer.internet_protocol ,business.industry ,Applied Mathematics ,Biology ,computer.software_genre ,Biochemistry ,Computer Science Applications ,03 medical and health sciences ,Software ,Structural Biology ,Data integrity ,Scalability ,Multilocus sequence typing ,Common Gateway Interface ,The Internet ,Perl ,business ,Molecular Biology ,computer ,XML ,030304 developmental biology ,computer.programming_language - Abstract
Multi-locus sequence typing (MLST) is a method of typing that facilitates the discrimination of microbial isolates by comparing the sequences of housekeeping gene fragments. The mlstdbNet software enables the implementation of distributed web-accessible MLST databases that can be linked widely over the Internet. The software enables multiple isolate databases to query a single profiles database that contains allelic profile and sequence definitions. This separation enables isolate databases to be established by individual laboratories, each customised to the needs of the particular project and with appropriate access restrictions, while maintaining the benefits of a single definitive source of profile and sequence information. Databases are described by an XML file that is parsed by a Perl CGI script. The software offers a large number of ways to query the databases and to further break down and export the results generated. Additional features can be enabled by installing third-party (freely available) tools. Development of a distributed structure for MLST databases offers scalability and flexibility, allowing participating centres to maintain ownership of their own data, without introducing duplication and data integrity issues.
- Published
- 2004
14. Identification of Common Genetic Variation That Modulates Alternative Splicing.
- Author
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Hull, Jeremy, Campino, Susana, Rowlands, Kate, Man-Suen Chan, Copley, Richard R., Taylor, Martin S., Rockett, Kirk, Elvidge, Gareth, Keating, Brendan, Knight, Julian, and Kwiatkowski, Dominic
- Subjects
HUMAN genetic variation ,GENETIC engineering ,NUCLEOTIDE sequence ,GENETIC polymorphisms ,NUCLEOTIDES ,EXONS (Genetics) - Abstract
Alternative splicing of genes is an efficient means of generating variation in protein function. Several disease states have been associated with rare genetic variants that affect splicing patterns. Conversely, splicing efficiency of some genes is known to vary between individuals without apparent ill effects. What is not clear is whether commonly observed phenotypic variation in splicing patterns, and hence potential variation in protein function, is to a significant extent determined by naturally occurring DNA sequence variation and in particular by single nucleotide polymorphisms (SNPs). In this study, we surveyed the splicing patterns of 250 exons in 22 individuals who had been previously genotyped by the International HapMap Project. We identified 70 simple cassette exon alternative splicing events in our experimental system; for six of these, we detected consistent differences in splicing pattern between individuals, with a highly significant association between splice phenotype and neighbouring SNPs. Remarkably, for five out of six of these events, the strongest correlation was found with the SNP closest to the intron- exon boundary, although the distance between these SNPs and the intron-exon boundary ranged from 2 bp to greater than 1,000 bp. Two of these SNPs were further investigated using a minigene splicing system, and in each case the SNPs were found to exert cis-acting effects on exon splicing efficiency in vitro. The functional consequences of these SNPs could not be predicted using bioinformatic algorithms. Our findings suggest that phenotypic variation in splicing patterns is determined by the presence of SNPs within flanking introns or exons. Effects on splicing may represent an important mechanism by which SNPs influence gene function. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
15. mlstdbNet -- distributed multi-locus sequence typing (MLST) databases.
- Author
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Jolley, Keith A., Man-Suen Chan, and Maiden, Martin C. J.
- Subjects
- *
DATABASE management software , *COMPUTER software , *NUCLEOTIDE sequence , *XML (Extensible Markup Language) , *PERL (Computer program language) - Abstract
Background: Multi-locus sequence typing (MLST) is a method of typing that facilitates the discrimination of microbial isolates by comparing the sequences of housekeeping gene fragments. The mlstdbNet software enables the implementation of distributed web-accessible MLST databases that can be linked widely over the Internet. Results: The software enables multiple isolate databases to query a single profiles database that contains allelic profile and sequence definitions. This separation enables isolate databases to be established by individual laboratories, each customised to the needs of the particular project and with appropriate access restrictions, while maintaining the benefits of a single definitive source of profile and sequence information. Databases are described by an XML file that is parsed by a Perl CGI script. The software offers a large number of ways to query the databases and to further break down and export the results generated. Additional features can be enabled by installing third-party (freely available) tools. Conclusion: Development of a distributed structure for MLST databases offers scalability and flexibility, allowing participating centres to maintain ownership of their own data, without introducing duplication and data integrity issues. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
16. An Analytical Model of Plant Virus Disease Dynamics with Roguing and Replanting
- Author
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Man-Suen Chan and Michael Jeger
- Subjects
Roguing ,education.field_of_study ,Veterinary medicine ,Qualitative analysis ,Ecology ,Disease management (agriculture) ,Plant virus ,Population ,Disease ,Virus diseases ,Biology ,education ,Highly sensitive - Abstract
The dynamics of a virus disease in a perennial plant population are modelled. The population is divided into healthy, latently infected, infectious and post-infectious plants and linked differential equations describe the dynamics of each category. Qualitative analysis of this model shows stable dynamics and threshold conditions for disease persistence. Stable equilibria are reached after several years. The dynamics of the model are highly sensitive to changes in contact rate and infectious period. Disease management by roguing (removal) of infected plants and replanting with healthy ones is investigated. Roguing only in the post-infectious category confers no advantage. At low contact rates, roguing only when plants become infectious is sufficient to eradicate the disease (...)
- Published
- 1994
17. Haplotype Homozygosity and Derived Alleles in the Human Genome
- Author
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Clare Trafford, Kirk A. Rockett, Dominic P. Kwiatkowski, Andrew E. Fry, Man-Suen Chan, and Martin Kimber
- Subjects
Linkage disequilibrium ,Biology ,Genome ,Chimpanzee genome project ,03 medical and health sciences ,Modal haplotype ,0302 clinical medicine ,Report ,Genetics ,Humans ,Genetics(clinical) ,International HapMap Project ,Alleles ,Genetics (clinical) ,030304 developmental biology ,0303 health sciences ,Genome, Human ,Homozygote ,Haplotype ,Age Factors ,Haplotypes ,Evolutionary biology ,Human genome ,Haplotype estimation ,030217 neurology & neurosurgery - Abstract
Haplotype-based techniques are being used to estimate the relative age of alleles--particularly in screening loci for signals of recent positive selection--but does this approach capture even coarse age differences? Using simulations and empirical data from the International HapMap Project, we show that a simple pairwise metric of haplotype homozygosity gives significantly higher mean values for human single-nucleotide-polymorphism alleles that appear to be derived than for those that appear to be ancestral, as determined by comparison with the chimpanzee genome. Our results support the use of haplotype-based techniques, such as extended haplotypic homozygosity, to assess the age of alleles.
- Full Text
- View/download PDF
18. Genetic and antigenic characterization of Canadian invasive Neisseria meningitidis serogroup C (MenC) case isolates in the post-MenC conjugate vaccine era, 2009–2013
- Author
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Tsang, Raymond, Hoang, Linda, Tyrrell, Greg, Horsman, Greg, Wylie, John, Jamieson, Frances, Lefebvre, Brigitte, Taha, Muhamed-Kheir, National Microbiology Laboratory [Winnipeg, Canada], Public Health Agency of Canada, BC Public Health Microbiology and Reference Laboratory, Provincial Laboratory for Public Health [Alberta, Canada] (ProvLab), Saskatchewan Disease Control Laboratory [Saskatchewan, Canada], Cadham Provincial Public Health Laboratory [Canada], Public Health Ontario - Santé publique Ontario, University of Toronto, Institut National de Santé Publique du Québec [Canada] (INSPQ), Centre National de Référence des Méningocoques et Haemophilus influenzae - National Reference Center Meningococci and Haemophilus influenzae (CNR), Institut Pasteur [Paris], We thank the staff of the National Microbiology Laboratory’s DNA Core Facility for providing primers and help with DNA sequencing. We also thank Dennis Law, Jianwei Zhou and Saul Deng for technical assistance. This study made use of the Neisseria MLST website ( http://pubmlst.org/neisseria/), developed by Keith Jolley and Man-Suen Chan, and sited at the University of Oxford, UK. The development of this site has been funded by the Wellcome Trust and European Union., and Institut Pasteur [Paris] (IP)
- Subjects
Microbiology (medical) ,MESH: Sequence Analysis, DNA ,Microbiology ,MESH: Meningococcal Vaccines ,MESH: Genotype ,MESH: Aged, 80 and over ,MESH: Canada ,MESH: Child ,MESH: Neisseria meningitidis, Serogroup C ,MESH: Molecular Epidemiology ,MESH: Genetic Variation ,MESH: Bacterial Proteins ,MESH: Adolescent ,MESH: Aged ,MESH: Humans ,MESH: Middle Aged ,MESH: Porins ,MESH: Molecular Typing ,MESH: Bacterial Outer Membrane Proteins ,MESH: Child, Preschool ,MESH: Meningitis, Meningococcal ,MESH: Adult ,MESH: Serogroup ,General Medicine ,MESH: Infant ,[SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology ,MESH: Male ,3. Good health ,MESH: Young Adult ,[SDV.SPEE]Life Sciences [q-bio]/Santé publique et épidémiologie ,MESH: Female ,MESH: Antigens, Bacterial - Abstract
International audience; We previously reported a shift in the electrophoretic type (ET) of invasive MenC in Canada from predominantly ET-15 to ET-37 in the post-MenC conjugate vaccine period. This study sought to confirm this trend by examining all culture-confirmed invasive MenC case isolates in Canada in the period from 1 January 2009 to 31 December 2013. Of the 50 MenC isolates, 18 belonged to ET-15, 28 belonged to ET-37 (but not ET-15), and four belonged to other clonal types. Analysis of the serotype and serosubtype antigens, porA and fetA gene sequences provided data to show that invasive MenC belonging to ET-15 and ET-37 were two very different subpopulations within the ST-11 clonal complex. Sequence analysis of the fHbp genes suggested that 12 different types of factor H-binding protein were found among the ET-15 isolates while 86 % of ET-37 isolates were found to have fHbp genes predicted to encode peptide 22. The nadA gene in 12 MenC isolates was disrupted due to IS1301 insertion and 11 of these 12 isolates belonged to ET-15. Ten per cent of the invasive MenC were found to have a frame-shift mutation in their fHbp genes that predicted no fHbp produced. Significant diversity and frame-shift mutations of fHbp genes were found in invasive MenC strains in Canada.
- Published
- 2015
19. Detection of a geographical and endemic cluster of hyper-invasive meningococcal strains
- Author
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Thierry de Baere, Corinne Ruckly, Sophie Bertrand, Jean-Marc Collard, Muhamed-Kheir Taha, Raymond Vanhoof, Eva Van Meervenne, Françoise Carion, Institut Scientifique de Santé Publique [Belgique] - Scientific Institute of Public Health [Belgium] (WIV-ISP), Réseau International des Instituts Pasteur (RIIP), Centre de Recherche Médicale et Sanitaire (Niamey, Niger) (CERMES), Infections Bactériennes Invasives, Institut Pasteur [Paris] (IP), In Belgium, this work was financed in part by the Federal Public Health Service. This publication made use of the Neisseria Multi Locus Sequence Typing website (http://pubmlst.org/neisseria/) developed by Keith Jolley and Man-Suen Chan and sited at the University of Oxford. The development of this site has been funded by the Wellcome Trust and European Union., and Institut Pasteur [Paris]
- Subjects
Male ,Serotype ,MESH: Geography ,Neisseria meningitidis, Serogroup B ,MESH: Genome, Bacterial ,MESH: Meningococcal Infections ,medicine.disease_cause ,Disease Outbreaks ,MESH: Belgium ,Belgium ,Genotype ,Cluster Analysis ,MESH: Disease Outbreaks ,MESH: Evolution, Molecular ,MESH: Aged ,Genetics ,Gel electrophoresis ,MESH: Microbial Sensitivity Tests ,0303 health sciences ,MESH: Middle Aged ,Geography ,biology ,Neisseria meningitidis ,Middle Aged ,MESH: Infant ,Electrophoresis, Gel, Pulsed-Field ,MESH: Multilocus Sequence Typing ,MESH: Electrophoresis, Gel, Pulsed-Field ,Infectious Diseases ,MESH: Young Adult ,Child, Preschool ,Female ,Neisseriaceae ,Adult ,DNA, Bacterial ,Adolescent ,Immunology ,Microbial Sensitivity Tests ,Meningococcal disease ,Microbiology ,Evolution, Molecular ,Young Adult ,03 medical and health sciences ,MESH: Neisseria meningitidis, Serogroup B ,medicine ,Humans ,Serotyping ,Aged ,Retrospective Studies ,030304 developmental biology ,MESH: Adolescent ,MESH: Humans ,030306 microbiology ,MESH: Child, Preschool ,MESH: Serotyping ,Infant ,Outbreak ,MESH: Adult ,MESH: Retrospective Studies ,medicine.disease ,biology.organism_classification ,MESH: Cluster Analysis ,MESH: DNA, Bacterial ,Virology ,MESH: Male ,Meningococcal Infections ,Multilocus sequence typing ,[SDV.SPEE]Life Sciences [q-bio]/Santé publique et épidémiologie ,MESH: Female ,Genome, Bacterial ,Multilocus Sequence Typing - Abstract
International audience; From 2006 to December 2009, 45 out of the 513 strains isolated from patients with invasive meningococcal disease in Belgium, were identified as Neisseria meningitidis serogroup B, non-serotypeable, subtype P1.14 (B:NT:P1.14). Most cases were geographically clustered in the northern part of the country. Multilocus Sequence Typing and antigen gene sequencing combined with Pulsed-Field Gel electrophoresis were used to investigate this cluster. Molecular typing showed that 39 out of these 45 N. meningitidis strains belonged to the clonal complex cc-269. The presence of the same PorA Variable Regions (VR1-VR2: 22, 14), the FetA allele (F5-1) and the highly similar Pulsed-Field Gel Electrophoresis profiles, supported genetic relatedness for 38 out of these 39 isolates. Retrospective analysis of B:NT:P1.22,14 isolates from 1999 onwards suggested that these strains belonging to the cc-269 complex, first emerged in the Belgian province of West-Flanders in 2004. This study showed that the combination of molecular tools with classical methods enabled reliable outbreak detection as well as a cluster identification.
- Published
- 2011
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