Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    Characterization of Coxiella burnetii outbreak strains
    Kuley, Runa - \ 2017
    Wageningen University. Promotor(en): M.A. Smits; J.M. Wells, co-promotor(en): A. Bossers. - Wageningen : Wageningen University - ISBN 9789463431514 - 226
    coxiella burnetii - q fever - outbreaks - strains - characterization - pathogenesis - zoonoses - virulence - dna sequencing - polymerase chain reaction - livestock farming - netherlands - coxiella burnetii - q-koorts - uitbraken (ziekten) - stammen (biologisch) - karakterisering - pathogenese - zoönosen - virulentie - dna-sequencing - polymerase-kettingreactie - veehouderij - nederland

    Q fever is a worldwide zoonotic infectious disease caused by the bacterium Coxiella burnetii. During 2007-2010, the largest Q fever outbreak was reported in The Netherlands, where more than 4000 human cases were registered showing a serious burden of the disease. During this outbreak, goats harboring predominantly the CbNL01 genotype strain were identified as the major source of disease in humans and drastic measures such as mass culling of infected goats were implemented to reduce the spread of the pathogen and control the disease. In order to minimize such complications in the future, it is crucial to have a thorough understanding of the disease causing pathogen and to develop effective Q fever vaccines. The causes of the large Dutch outbreak are not well-understood and one of the main reasons speculated were the hyper-virulent behavior of the circulating C. burnetii isolates. The research described in this thesis focuses on the characterization of C. burnetii outbreak strains isolated from infected goats, cattle, sheep and human clinical materials. Our studies were initiated to better understand the bacterial pathogenesis, virulence, evolution, adaptations in various environments, host immune responses and to identify pathogen related factors that have modulated the disease outbreak. We specifically aimed to identify the virulence factors and mechanisms that contributed to the increased zoonotic potential of the strain associated with the Dutch Q fever outbreak.

    The studies presented in this thesis majorly applied Pathogenomic approaches at the genome and transcriptome level to decipher host-pathogen interactions and to develop new tools to study C. burnetii infections. A transcriptome analysis of the outbreak C. burnetii strain of the CbNL01 genotype grown under in vivo and in vitro conditions resulted in the identification of distinct metabolic adaptations and virulence mechanisms of the bacterium. Detailed comparative analysis of complete genome sequences of C. burnetii strains showed a high similarity between strains of the same genotype. Genome sequences of the Dutch outbreak CbNL01 genotype strains were more divergent than the genome sequences of the less prevalent CbNL12 genotype strains and the NM reference strain. The analysis also showed that the high virulence of the outbreak strains was not associated with acquiring novel virulence-related genes arguing against the idea that the Dutch outbreak was due to emergence of hyper-virulent strains though horizontal gene transfer. Among the prominent genetic differences in the CbNL01 outbreak strains compared to CbNL12 and NM, were the presence of several point mutations and increased transposon mediated genome plasticity, which might have contributed to its epidemic potential. Point mutations, especially in a large number of membrane proteins, could also have contributed to the increased zoonotic potential of CbNL01 strains allowing this clone to escape the host immune responses in goats and humans. In addition, mutations in critical genes involved in virulence and evasion of the host immune system could be potentially involved in the increased virulence of the CbNL01 outbreak strains. On the contrary, studies on host immune responses in an in vivo (experimental infections in mice) and an in vitro (human PBMC’s stimulation) model did not show any difference associated with the strain genotype. However, differences in immune responses were found to be associated with the host-origin of the C. burnetii strains. Among different host-origin strains, strains derived from goats and humans generated significantly lower innate and adaptive immune responses than strains derived from cattle, whereas no differences in immune responses were observed when strains were grouped based upon their genotype. These observations support immune evasions as a major virulence strategy of goat and human strains in hosts and further suggest that bacteria originating from goats have a greater potential to cause outbreaks in humans. This indicates that for Q fever prevention purposes goats should be efficiently monitored for the presence of C. burnetii. Taken together, the results described in this thesis suggest that the virulence potential of C. burnetii strains is not only based on genetic differences, but also on other host-adaptation mechanisms such as transposition of genomic elements and/or differential regulation of gene expression. Finally, the results from this thesis provide a framework for future studies in the development of vaccines and diagnostic tools for Q fever.

    Are all eggs equal? : embryonic development and nutrient metabolism in chicken eggs of different origins
    Nangsuay, A. - \ 2016
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; R. Meijerhof. - Wageningen : Wageningen University - ISBN 9789462577749 - 213
    eggs - hens - broilers - characteristics - strains - embryonic development - nutrients - metabolism - hatcheries - poultry - nutrition physiology - eieren - hennen - vleeskuikens - karakteristieken - stammen (biologisch) - embryonale ontwikkeling - voedingsstoffen - metabolisme - broedinstallaties - pluimvee - voedingsfysiologie

    Hatching eggs, supplied to hatcheries are originating from different origins varying in breed, strain, and breeder age. These hatching eggs can be different in size, composition and eggshell properties, which might influence nutrient and O2 availability and consequently could affect embryonic development and nutrient metabolism. The aim of this thesis was therefore 1) to investigate effects of egg origin on nutrient and O2 availability, 2) to investigate effects of egg origins on nutrient metabolism and embryonic development and 3) to investigate consequences of different egg origins on the incubation process and hatching characteristics. In five studies, effects of different egg origins on nutrient and O2 availability, nutrient metabolism, embryo development and hatching characteristics were investigated. The first and second study focused on breeder age and egg size. The third study on breed; broilers and layers. The fourth study on broiler strain and the fifth study on breeder age, strain and eggshell temperature (EST). The overall findings in this thesis suggest that hatching eggs from different origins are not equal in availability of nutrients and O2. Nutrient availability is altered through variation in yolk size, especially by the effects of breeder age and breed. O2 availability is altered by differences in eggshell properties, which is influenced by especially breed and broiler strain. The availability of both nutrients and O2 plays a role on nutrient metabolism measured as embryonic heat production (HP) and consequently on embryonic development. Between incubation day (E) E7 and E14, both nutrient and O2 availability might affect nutrient metabolism as shown in the results of the broiler and layer comparison. Between E14 and hatching, the availability of O2 becomes the most determinant factor for nutrient metabolism and consequently for embryonic development. An increase in EST from 37.8 to 38.9°C from E7 onward resulted in an acceleration of nutrient metabolism and embryonic development until E16, but thereafter a high EST resulted in reduced yolk free body mass development. Embryos with an accelerated metabolic speed at an early stage of incubation, caused by an increased EST, might reach limited O2 availability at a higher magnitude than the embryos at a normal EST. As a result, nutrient metabolism is restricted and embryonic development is depressed. It can be concluded that not only the HP, but also the availability of O2 is crucial to be taken into account for developing incubator temperature. The principle is to obtain an optimal EST, which could maintain the balance between O2 requirement (driven by nutrient metabolism) and O2 availability for a continuing optimal nutrient metabolism to generate sufficient energy for embryonic development throughout incubation.

    Phenotypic and genetic diversity of the species Lactobacillus rhamnosus
    Ceapa, C.D. - \ 2016
    Wageningen University. Promotor(en): Michiel Kleerebezem; Jan Knol; J. Lambert. - Wageningen : Wageningen University - ISBN 9789462576285 - 195
    fermentation products - probiotics - intestinal microorganisms - lactic acid bacteria - strains - medicinal properties - genomics - nutrition and health - fermentatieproducten - probiotica - darmmicro-organismen - melkzuurbacteriën - stammen (biologisch) - medicinale eigenschappen - genomica - voeding en gezondheid

    The thesis explores the diversity of Lactobacillus rhamnosus, a species from which strains are studied for their anti-inflammatory, anti-allergic, and diarrhea preventing effects. The work combines observations on the behavior of the bacteria in a simplified laboratory setting (use of carbohydrates, immune modulation effects, anti-pathogenic effects) with genomic information obtained by sequencing, with the aim to pinpoint genes that could be relevant for bacterial survival and metabolic capacities. Phenotypic and genotypic profiling analyses congruently revealed that carbohydrate metabolism and transport is essential for this species’ adaptation to the environment. Genotype–phenotype correlation analysis enabled us to predict and then experimentally verify genes responsible for the utilization of L-Sorbose, L-Fucose α-D-Methyl Glycoside.

    Diversity of acid stress resistant variants of Listeria monocytogenes and the potential role of ribosomal protein S21 encoded by rpsU
    Metselaar, K.I. ; Besten, H.M.W. den; Boekhorst, J. ; Hijum, S.A.F.T. van; Zwietering, M.H. ; Abee, T. - \ 2015
    Frontiers in Microbiology 6 (2015). - ISSN 1664-302X - 12 p.
    high hydrostatic-pressure - gamma-aminobutyric-acid - microtiter plate assay - glutamate-decarboxylase - bacillus-subtilis - escherichia-coli - low ph - genes - strains - inactivation
    The dynamic response of microorganisms to environmental conditions depends on the behavior of individual cells within the population. Adverse environments can select for stable stress resistant subpopulations. In this study, we aimed to get more insight in the diversity within Listeria monocytogenes LO28 populations, and the genetic basis for the increased resistance of stable resistant fractions isolated after acid exposure. Phenotypic cluster analysis of 23 variants resulted in three clusters and four individual variants and revealed multiple-stress resistance, with both unique and overlapping features related to stress resistance, growth, motility, biofilm formation, and virulence indicators. A higher glutamate decarboxylase activity correlated with increased acid resistance. Whole genome sequencing revealed mutations in rpsU, encoding ribosomal protein S21 in the largest phenotypic cluster, while mutations in ctsR, which were previously shown to be responsible for increased resistance of heat and high hydrostatic pressure resistant variants, were not found in the acid resistant variants. This underlined that large population diversity exists within one L. monocytogenes strain and that different adverse conditions drive selection for different variants. The finding that acid stress selects for rpsU variants provides potential insights in the mechanisms underlying population diversity of L. monocytogenes.
    West Nile Virus: High Transmission Rate in North-Western European Mosquitoes Indicates Its Epidemic Potential and Warrants Increased Surveillance
    Fros, J.J. ; Geertsema, C. ; Vogels, C.B.F. ; Roosjen, P.P.J. ; Failloux, A.B. ; Vlak, J.M. ; Koenraadt, C.J.M. ; Takken, W. ; Pijlman, G.P. - \ 2015
    PLoS Neglected Tropical Diseases 9 (2015)7. - ISSN 1935-2727
    united-states - differential virulence - experimental-infection - vector competence - lineage 1 - outbreak - circulation - strains - disease - encephalitis
    West Nile virus (WNV) is on the rise in Europe, with increasing numbers of human cases of neurological disease and death since 2010. However, it is currently unknown whether or not WNV will continue to spread to north-western Europe (NWE), in a fashion similar to the WNV epidemic sweep in the United States (1999–2004). The presence of competent mosquitoes is a strict requirement for WNV transmission, but no laboratory studies have been conducted with the new European lineage 2 WNV outbreak strain. Our study is the first to investigate transmissibility in NWE Culex pipiens for lineage 2 WNV in a systematic, direct comparison with North American Culex pipiens and with the lineage 1 WNV strain. We demonstrate that European mosquitoes are highly competent for both WNV lineages, which underscores the epidemic potential ofWNV in Europe. However, the transmission rate for lineage 2 WNV was significantly lower in North American mosquitoes, which indicates different risk levels between both continents for lineage 2 but not lineage 1 WNV. Based on our result, we propose that WNV surveillance in mosquitoes and birds must be intensified in Europe to allow early detection, timely intervention strategies and prevent outbreaks of WNV neurological disease.
    Naar een beter substraatgebruik in de champignonteelt via rassen : een genetische analyse
    Baars, J.J.P. ; Sonnenberg, A.S.M. - \ 2015
    Wageningen : Plant Research International (Rapport / Plant Research International 2015-2) - 20
    eetbare paddestoelen - agaricus bisporus - veredelen - kruisingen - stammen (biologisch) - genetische bronnen - segregatie - materialen uit biologische grondstoffen - substraten - edible fungi - agaricus bisporus - breeding - crosses - strains - genetic resources - segregation - biobased materials - substrates
    In 2014 is een nieuwe stap gezet in het project om tot een efficienter substraatgebruik te komen in de champignonteelt. Deze stap heeft twee doelen: • Het bepalen van de breeding value (hoe gedragen de stammen zich in kruisingen en welke waarde hebben ze dus in de veredeling) • Welke lijnen zijn geschikt om segregerende populaties te maken. Deze populaties zullen gebruikt worden om genomische gebieden/genen te vinden die de verschillen in efficientie in substraat gebruik kunnen verklaren. De kennis kan gebruikt worden voor zowel veredelen op substraatgebruik als het vinden van alternatieve grondstoffen voor het maken van substraat.
    Quantitative trait locus mapping for bruising sensitivity and cap color of Agaricus bisporus (button mushrooms)
    Gao, W. ; Weijn, A. ; Baars, J.J.P. ; Mes, J.J. ; Visser, R.G.F. ; Sonnenberg, A.S.M. - \ 2015
    Fungal Genetics and Biology 77 (2015). - ISSN 1087-1845 - p. 69 - 81.
    melanin biosynthesis pathway - latent isoform ppo4 - pseudomonas-tolaasii - genetic-analysis - tyrosinase - purification - behavior - strains - genome
    White button mushrooms discolor after mechanical damage of the cap skin. This hampers the development of a mechanical harvest system for the fresh market. To unravel the genetic basis for bruising sensitivity, two haploid populations (single spore cultures) were generated derived from crosses between parental lines differing in discoloration after mechanical damage (bruising sensitivity). The haploids were crossed with different homokaryotic tester lines to generate mushrooms and allow assessment of the bruising sensitivity in different genetic backgrounds. Bruising sensitivity appears to be a polygenic highly heritable trait (H2: 0.88-0.96) and a significant interaction between genotypes and tester lines and genotypes and flushes was found. Using SNP markers evenly spread over all chromosomes, a very low recombination was found between markers allowing only assignment of QTL for bruising sensitivity to chromosomes and not to sub-regions of chromosomes. The cap color of the two parental lines of population 1 is white and brown respectively. A major QTL for bruising sensitivity was assigned to chromosome 8 in population 1 that also harbors the main determinant for cap color (brown versus white). Splitting offspring in white and non-white mushrooms made minor QTL for bruising sensitivity on other chromosomes (e.g. 3 and 10) more prominent. The one on chromosome 10 explained 31% phenotypic variation of bruising sensitivity in flush 2 in the subpopulations of population 1. The two parental lines of population 2 are both white. Major QTL of bruising sensitivity were detected on chromosome 1 and 2, contributing totally more than 44% variation of the bruising sensitivity in flush 1 and 54% variation of that in flush 2. A considerable consistency was found in QTL for bruising sensitivity in the different populations studied across tester lines and flushes indicating that this study will provide a base for breeding cultivars that are less sensitive for bruising allowing the use of mechanical harvest and automatic postharvest handling for produce for the fresh market. The low recombination between homologous chromosomes, however, underlines the need to introduce a normal recombination pattern found in a subspecies of the button mushroom.
    Cell-Free Propagation of Coxiella burnetii Does Not Affect Its Relative Virulence
    Kuley, R. ; Smith, H.E. ; Frangoulidis, D. ; Smits, M.A. ; Roest, H.I.J. ; Bossers, A. - \ 2015
    PLoS ONE 10 (2015)3. - ISSN 1932-6203 - 16 p.
    real-time pcr - q-fever - ethidium monoazide - phase-ii - propidium monoazide - dead cells - t-cells - lipopolysaccharide - infection - strains
    Q fever is caused by the obligate intracellular bacterium Coxiella burnetii. In vitro growth of the bacterium is usually limited to viable eukaryotic host cells imposing experimental constraints for molecular studies, such as the identification and characterisation of major virulence factors. Studies of pathogenicity may benefit from the recent development of an extracellular growth medium for C. burnetii. However, it is crucial to investigate the consistency of the virulence phenotype of strains propagated by the two fundamentally different culturing systems. In the present study, we assessed the viability of C. burnetii and the lipopolysaccaride (LPS) encoding region of the bacteria in both culture systems as indirect but key parameters to the infection potential of C. burnetii. Propidium monoazide (PMA) treatment-based real-time PCR was used for enumeration of viable C. burnetii which were validated by fluorescent infectious focus forming unit counting assays. Furthermore, RNA isolated from C. burnetiipropagated in both the culture systems was examined for LPS-related gene expression. All thus far known LPS-related genes were found to be expressed in early passages in both culturing systems indicating the presence of predominantly the phase I form of C. burnetii. Finally, we used immune-competent mice to provide direct evidence, that the relative virulence of different C. burnetii strains is essentially the same for both axenic and cell-based methods of propagation.
    High natural antibody titers of indigenous chickens are related with increased hazard in confinement
    Wondmeneh, E. ; Arendonk, J.A.M. van; Waaij, E.H. van der; Ducro, B.J. ; Parmentier, H.K. - \ 2015
    Poultry Science 94 (2015)7. - ISSN 0032-5791 - p. 1493 - 1498.
    laying hens - responses - survival - immunity - corticosterone - population - strains - stress - innate - plasma
    Natural antibody (NAb) levels and survival rates were evaluated in 4 breeds of laying hens in Ethiopia: indigenous, improved indigenous, exotic layer, and crossbred. Titers of NAb isotypes IgG and IgM binding keyhole limpet hemocyanin (KLH) in serum were measured at 20, 26, 35, and 45 wk age. Repeated-measure ANOVA showed that IgG and IgM levels vary with time within each breed (P <0.05). Indigenous chickens had significantly (P <0.05) higher NAb levels at all ages. The Cox proportional hazard analysis showed increased hazard with increased levels of NAbs in the exotic layers (P <0.05). However, the reduced hazards with increased levels of NAbs were not significant in the improved indigenous and crossbred chickens. Indigenous chickens showed increased hazard with increasing levels of NAb (P > 0.05). We concluded that not only the NAb levels but also the effect of Nabs on survival vary between indigenous and improved breeds. The results indicate that NAb levels are associated with survival in elite (improved) breeds, but are associated with increased hazard in indigenous chickens.
    Effect of sublethal preculturing on the survival of probiotics and metabolite formation in set-yoghurt
    Settachaimongkon, S. ; Valenberg, H.J.F. van; Winata, V. ; Wang, X. ; Nout, M.J.R. ; Hooijdonk, A.C.M. van; Zwietering, M.H. ; Smid, E.J. - \ 2015
    Food Microbiology 49 (2015). - ISSN 0740-0020 - p. 104 - 115.
    lactic-acid bacteria - fermented milks - tolerance response - functional foods - stress responses - bifidobacteria - lactobacillus - cultures - strains - microorganisms
    The objective of this study was to investigate the effect of preculturing of Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp. lactis BB12 under sublethal stress conditions on their survival and metabolite formation in set-yoghurt. Prior to co-cultivation with yoghurt starters in milk, the two probiotic strains were precultured under sublethal stress conditions (combinations of elevated NaCl and low pH) in a batch fermentor. The activity of sublethally precultured probiotics was evaluated during fermentation and refrigerated storage by monitoring bacterial population dynamics, milk acidification and changes in volatile and non-volatile metabolite profiles of set-yoghurt. The results demonstrated adaptive stress responses of the two probiotic strains resulting in their viability improvement without adverse influence on milk acidification. A complementary metabolomic approach using SPME-GC/MS and 1H-NMR resulted in the identification of 35 volatiles and 43 non-volatile polar metabolites, respectively. Principal component analysis revealed substantial impact of the activity of sublethally precultured probiotics on metabolite formation demonstrated by distinctive volatile and non-volatile metabolite profiles of set-yoghurt. Changes in relative abundance of various aroma compounds suggest that incorporation of stress-adapted probiotics considerably influences the organoleptic quality of product. This study provides new information on the application of stress-adapted probiotics in an actual food-carrier environment
    Two distinct groups within the Bacillus subtilis group display significantly different spore heat resistance properties
    Berendsen, E.M. ; Zwietering, M.H. ; Kuipers, O.P. ; Wells-Bennik, M.H.J. - \ 2015
    Food Microbiology 45 (2015). - ISSN 0740-0020 - p. 18 - 25.
    thermal inactivation - bacterial-spores - sporulation - food - sporothermodurans - strains - systems - milk - stearothermophilus - temperatures
    The survival of bacterial spores after heat treatment and the subsequent germination and outgrowth in a food product can lead to spoilage of the food product and economical losses. Prediction of time-temperature conditions that lead to sufficient inactivation requires access to detailed spore thermal inactivation kinetics of relevant model strains. In this study, the thermal inactivation kinetics of spores of fourteen strains belonging to the Bacillus subtilis group were determined in detail, using both batch heating in capillary tubes and continuous flow heating in a micro heater. The inactivation data were fitted using a log linear model. Based on the spore heat resistance data, two distinct groups (p <0.001) within the B. subtilis group could be identified. One group of strains had spores with an average D120 °C of 0.33 s, while the spores of the other group displayed significantly higher heat resistances, with an average D120 °C of 45.7 s. When comparing spore inactivation data obtained using batch- and continuous flow heating, the z-values were significantly different, hence extrapolation from one system to the other was not justified. This study clearly shows that heat resistances of spores from different strains in the B. subtilis group can vary greatly. Strains can be separated into two groups, to which different spore heat inactivation kinetics apply.
    Rapid method to screen and sort lipid accumulating microalgae
    Dominguez Teles, I. ; Zwart, M. van der; Kleinegris, D.M.M. ; Barbosa, M.J. ; Wijffels, R.H. - \ 2015
    Bioresource Technology 184 (2015). - ISSN 0960-8524 - p. 47 - 52.
    fatty-acid profile - fluorescence method - nannochloropsis sp - nile red - biodiesel - biofuels - strains
    The present work established an efficient staining method for fluorescence activated cell sorting (FACS) with Chlorococcum littorale maintaining cellular viability. The method was designed to detect high-lipid cells and to guarantee cellular viability. BODIPY505/515 (BP) was more suitable to FACS when compared to Nile red. The optimum concentrations were 0.4 µg ml-1 of BP, 0.1% DMSO or 0.35% ethanol. Both ethanol and DMSO were equally efficient and assured cellular viability after the staining and sorting. Here a method is presented to rapidly screen and sort lipid rich cells of C. littorale with FACS, which can be used to produce new inoculum with increased cellular lipid content.
    Evidence of Evolving Extraintestinal Enteroaggregative Escherichia coli ST38 Clone
    Chattaway, M.A. ; Jenkins, C. ; Ciesielczuk, H. ; Day, M. ; DoNascimento, V. ; Day, M.M. ; Rodriguez, I. ; Essen-Zandbergen, A. van; Schink, A.K. ; Wu, G.H. ; Threlfall, J. ; Woodward, M.J. ; Coldham, N. ; Kadlec, K. ; Schwarz, S. ; Dierikx, C. ; Guerra, B. ; Helmuth, R. ; Mevius, D.J. ; Woodford, N. ; Wain, J. - \ 2014
    Emerging Infectious Diseases 20 (2014)11. - ISSN 1080-6040 - p. 1935 - 1937.
    Comparative population structure analysis of Campylobacter jejuni from human and poultry origin in Bangladesh
    Islam, Z. ; Belkum, A. van; Wagenaar, J.A. ; Cody, A.J. ; Boer, A.G. de; Sarker, S.K. ; Jacobs, B.C. ; Talukder, K.A. ; Endtz, H.P. - \ 2014
    European Journal of Clinical Microbiology and Infectious Diseases 33 (2014)12. - ISSN 0934-9723 - p. 2173 - 2181.
    fragment-length polymorphism - guillain-barre-syndrome - field gel-electrophoresis - miller-fisher-syndromes - sequence typing system - short variable region - genetic diversity - molecular characterization - strains - epidemiology
    Campylobacter jejuni is the most important cause of antecedent infections leading to Guillain-Barr, syndrome (GBS) and Miller Fisher syndrome (MFS). The objective of the present study was to define the genetic diversity, population structure, and potential role of poultry in the transmission of Campylobacter to humans in Bangladesh. We determined the population structure of C. jejuni isolated from poultry (n = 66) and patients with enteritis (n = 39) or GBS (n = 10). Lipooligosaccharide (LOS) typing showed that 50/66 (76 %) C. jejuni strains isolated from poultry could be assigned to one of five LOS locus classes (A-E). The distribution of neuropathy-associated LOS locus classes A, B, and C were 30/50 (60 %) among the typable strains isolated from poultry. The LOS locus classes A, B, and C were significantly associated with GBS and enteritis-related C. jejuni strains more than for the poultry strains [(31/38 (82 %) vs. 30/50 (60 %), p <0.05]. Multilocus sequence typing (MLST) defined 15 sequence types (STs) and six clonal complexes (CCs) among poultry isolates, including one ST-3740 not previously documented. The most commonly identified type, ST-5 (13/66), in chicken was seen only once among human isolates (1/49) (p <0.001). Amplified fragment length polymorphism (AFLP) revealed three major clusters (A, B, and C) among C. jejuni isolated from humans and poultry. There seems to be a lack of overlap between the major human and chicken clones, which suggests that there may be additional sources for campylobacteriosis other than poultry in Bangladesh.
    Campylobacter fetus subsp. testudinum subsp. nov., isolated from humans and reptiles
    Fitzgerald, C. ; Tu, Z.C. ; Patrick, M. ; Stiles, T. ; Lawson, A.J. ; Santovenia, M. ; Gilbert, M.J. ; Bergen, M. von; Joyce, K. ; Pruckler, J. ; Stroika, S. ; Duim, B. ; Miller, W.G. ; Loparev, V. ; Sinnige, J.C. ; Fields, P.I. ; Tauxe, R.V. ; Blaser, M.J. ; Wagenaar, J.A. - \ 2014
    International Journal of Systematic and Evolutionary Microbiology 64 (2014). - ISSN 1466-5026 - p. 2944 - 2948.
    genus campylobacter - pcr assay - differentiation - identification - strains - origins
    A polyphasic study was undertaken to determine the taxonomic position of 13 Campylobacter fetus-like strains from humans (n=8) and reptiles (n=5). The results of matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) MS and genomic data from sap analysis, 16S rRNA gene and hsp60 sequence comparison, pulsed-field gel electrophoresis, amplified fragment length polymorphism analysis, DNA-DNA hybridization and whole genome sequencing demonstrated that these strains are closely related to C. fetus but clearly differentiated from recognized subspecies of C. fetus. Therefore, this unique cluster of 13 strains represents a novel subspecies within the species C. fetus, for which the name Campylobacter fetus subsp. testudinum subsp. nov. is proposed, with strain 03-427(T) (=ATCC BAA-2539(T)=LMG 27499(T)) as the type strain. Although this novel taxon could not be differentiated from C. fetus subsp. fetus and C. fetus subsp. venerealis using conventional phenotypic tests, MALDI-TOF MS revealed the presence of multiple phenotypic biomarkers which distinguish Campylobacter fetus subsp. testudinum subsp. nov. from recognized subspecies of C. fetus.
    A SpoT polymorphism correlates with chill stress survival and is prevalent in clinical isolates of Campylobacter jejuni
    Nierop Groot, M.N. ; Boer, A.G. de; Pelt, W. van; Hulst-van Arkel, M.C. van der; Leeuw, P. ; Widjaja, H.C.A. ; Smits, M.A. ; Wal, F.J. van der - \ 2014
    Poultry Science 93 (2014)11. - ISSN 0032-5791 - p. 2900 - 2909.
    virulence-associated phenotypes - htra degp protein - chicken carcasses - escherichia-coli - broiler meat - poultry - colonization - strains - netherlands - expression
    Resistance of Campylobacter jejuni to environmental stress is regarded as a risk factor for the transmission of C. jejuni from poultry or poultry products to humans. So far, the mechanisms underlying the capacity of C. jejuni to survive environmental stress conditions are not fully understood. In this study, we searched for polymorphisms in C. jejuni genes, potentially involved in resistance to chill stress. To this end, we assessed 3 groups of C. jejuni isolates (clinical, retail chicken meat, and feces) for survival of experimentally induced chill stress. For each isolate we sequenced 3 genes encoding the C. jejuni sigma factors FliA, RpoD, and RpoN as well as the genes for the transcriptional regulator SpoT and the periplasmic protein HtrA. Data suggest a higher prevalence of a specific polymorphism in spoT in clinical isolates compared with poultry meat or farm isolates. Moreover, this genotype correlated with enhanced survival of chill stress. The observation that the prevalence of this SNP is relatively high in clinical isolates, which most likely have been exposed to multiple forms of stress, suggest that this SNP may be a biomarker for enhanced survival of stress.
    A naturally occurring nucleotide polymorphism in the orf2/folc promoter is associated with Streptococcus suis virulence
    Greeff, A. de; Buys, H. ; Wells, J.M. ; Smith, H.E. - \ 2014
    BMC Microbiology 14 (2014)1. - ISSN 1471-2180
    germ-free pigs - serotype-2 - strains - identification - cytokine - pathogen - suilysin - release - type-2 - cells
    Streptococcus suis is a major problem in the swine industry causing meningitis, arthritis and pericarditis in piglets. Pathogenesis of S. suis is poorly understood. We previously showed that introduction of a 3 kb genomic fragment from virulent serotype 2 strain 10 into a weakly virulent serotype 2 strain S735, generated a hypervirulent isolate. The 3 kb genomic fragment contained two complete open reading frames (ORF) in an operon-structure of which one ORF showed similarity to folylpolyglutamate synthetase, whereas the function of the second ORF could not be predicted based on database searches for protein similarity.
    Circulation of four Anaplasma phagocytophilum ecotypes in Europe
    Jahfari, S. ; Coipan, E.C. ; Fonville, M. ; Leeuwen, A.D. van; Hengeveld, P. ; Heylen, D. ; Heyman, P. ; Maanen, C. van; Butler, C.M. ; Foldvari, G. ; Szekeres, S. ; Duijvendijk, L.A.G. van; Tack, W. ; Rijks, J.M. ; Giessen, J. van der; Takken, W. ; Wieren, S.E. van; Takumi, K. ; Sprong, H. - \ 2014
    Parasites & Vectors 7 (2014)1. - ISSN 1756-3305
    candidatus neoehrlichia mikurensis - human granulocytic anaplasmosis - ixodes-ricinus ticks - borrelia-burgdorferi - borne diseases - phylogenetic analyses - sequence-analysis - ehrlichiosis - strains - gene
    Background: Anaplasma phagocytophilum is the etiological agent of granulocytic anaplasmosis in humans and animals. Wild animals and ticks play key roles in the enzootic cycles of the pathogen. Potential ecotypes of A. phagocytophilum have been characterized genetically, but their host range, zoonotic potential and transmission dynamics has only incompletely been resolved. Methods. The presence of A. phagocytophilum DNA was determined in more than 6000 ixodid ticks collected from the vegetation and wildlife, in 289 tissue samples from wild and domestic animals, and 69 keds collected from deer, originating from various geographic locations in The Netherlands and Belgium. From the qPCR-positive lysates, a fragment of the groEL-gene was amplified and sequenced. Additional groEL sequences from ticks and animals from Europe were obtained from GenBank, and sequences from human cases were obtained through literature searches. Statistical analyses were performed to identify A. phagocytophilum ecotypes, to assess their host range and their zoonotic potential. The population dynamics of A. phagocytophilum ecotypes was investigated using population genetic analyses. Results: DNA of A. phagocytophilum was present in all stages of questing and feeding Ixodes ricinus, feeding I. hexagonus, I. frontalis, I. trianguliceps, and deer keds, but was absent in questing I. arboricola and Dermacentor reticulatus. DNA of A. phagocytophilum was present in feeding ticks and tissues from many vertebrates, including roe deer, mouflon, red foxes, wild boar, sheep and hedgehogs but was rarely found in rodents and birds and was absent in badgers and lizards. Four geographically dispersed A. phagocytophilum ecotypes were identified, that had significantly different host ranges. All sequences from human cases belonged to only one of these ecotypes. Based on population genetic parameters, the potentially zoonotic ecotype showed significant expansion. Conclusion: Four ecotypes of A. phagocytophilum with differential enzootic cycles were identified. So far, all human cases clustered in only one of these ecotypes. The zoonotic ecotype has the broadest range of wildlife hosts. The expansion of the zoonotic A. phagocytophilum ecotype indicates a recent increase of the acarological risk of exposure of humans and animals.
    Bacillus anthracis-like bacteria and other B. cereus group members in a microbial community within the international space station: a challenge for rapid and easy molecular detection of virulent B. anthracis.
    Tongeren, S.P. van; Roest, H.I.J. ; Degener, J.E. ; Harmsen, H.J.M. - \ 2014
    PLoS ONE 9 (2014)9. - ISSN 1932-6203
    polymerase-chain-reaction - toxin genes - identification - purification - sequence - strains - gyrb
    For some microbial species, such as Bacillus anthracis, the etiologic agent of the disease anthrax, correct detection and identification by molecular methods can be problematic. The detection of virulent B. anthracis is challenging due to multiple virulence markers that need to be present in order for B. anthracis to be virulent and its close relationship to Bacillus cereus and other members of the B. cereus group. This is especially the case in environments where build-up of Bacillus spores can occur and several representatives of the B. cereus group may be present, which increases the chance for false-positives. In this study we show the presence of B. anthracis-like bacteria and other members of the B. cereus group in a microbial community within the human environment of the International Space Station and their preliminary identification by using conventional culturing as well as molecular techniques including 16S rDNA sequencing, PCR and real-time PCR. Our study shows that when monitoring the microbial hygiene in a given human environment, health risk assessment is troublesome in the case of virulent B. anthracis, especially if this should be done with rapid, easy to apply and on-site molecular methods.
    Quantification of transfer of Listeria monocytogenes between cooked ham and slicing machine surfaces
    Chaitiemwong, N. ; Hazeleger, W.C. ; Beumer, R.R. ; Zwietering, M.H. - \ 2014
    Food Control 44 (2014). - ISSN 0956-7135 - p. 177 - 184.
    bacterial cross-contamination - modeling transfer - stainless-steel - salmonella-typhimurium - exposure assessment - turkey breast - meat - environments - adherence - strains
    Transfer of Listeria monocytogenes was investigated from surface-inoculated cooked ham to commercial slicing machine surfaces, from spot-inoculated ham to the slicing machine blade, and vise-versa from a contaminated slicer to clean ham. With balances the proportion transfer from the source to the various destinations were investigated as well as the kinetics of transfer during successive slicing, using a difference equation. For inoculated ham, the transfer ratio to the machine was highest to the table (0.06), followed by the handle board (0.01) and plate, guard, and front and back of the blade (
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