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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Salmonella biofilms
    Castelijn, G.A.A. - \ 2013
    Wageningen University. Promotor(en): Tjakko Abee; Marcel Zwietering, co-promotor(en): Roy Moezelaar. - S.l. : s.n. - ISBN 9789461737335 - 168
    salmonella typhimurium - salmonella - biofilms - franjes - salmonella typhimurium - salmonella - biofilms - fimbriae

    Biofilm formation by Salmonellaspp. is a problem in the food industry, since biofilms may act as a persistent source of product contamination. Therefore the aim of this study was to obtain more insight in the processes involved and the factors contributing to Salmonellabiofilm formation. A collection of SalmonellaTyphimurium clinical, outbreak-related and retail product isolates, was used to determine biofilm formation capacity and to identify cellular parameters contributing to surface colonisation. The results revealed dense biofilm formation by these isolates at 25 °C and 37 °C in nutrient-rich media. However, in nutrient-low media dense biofilm formation was only observed at 25 °C with industrial isolates. In addition, temperature and medium composition were also found to influence biofilm morphology and composition. At nutrient-low conditions at 25 °C the biofilm consisted of cell clusters encapsulated by an extracellular matrix composed of curli fimbriae and cellulose. In nutrient-rich conditions a monolayer of cells with little to no extracellular matrix were observed, with a prominent role for type 1 fimbriae. This type of fimbriae was only expressed in a subset of strains and appeared to contribute to initial attachment of Salmonellacells ultimately leading to dense biofilm formation. This study also indicated that biofilm formation differs between and within the Salmonellaserovars Typhimurium, Derby, Brandenburg and Infantis, isolated from meat processing environments. And, for all serovars biofim formation contributed to the survival on stainless steel surfaces and biofilm cells were less susceptible to peracetic acid disinfection treatments. This latter effect was specifically observed in the presence of organic matter, which drastically decreased the activity of peracetic acid conceivably resulting in low level exposure of the bacterial flora facilitating survival. Furthermore, single and repeated exposure to sub-lethal concentrations of the disinfectant benzalkonium chloride rapidly selected for resistant variants. In conclusion, the results obtained in this study may contribute to the development of better strategies for Salmonella control in food processing environments.

    Waardevermindering pluimveevlees besmet met Salmonella enteritidis en Salmonella typhymurium
    Horne, P.L.M. van - \ 2011
    Den Haag : LEI Wageningen UR - 6
    salmonella enteritidis - salmonella typhimurium - pluimveevlees - voedselbesmetting - voedselveiligheid - vleeskuikens - pluimveehouderij - kosten - salmonella enteritidis - salmonella typhimurium - poultry meat - food contamination - food safety - broilers - poultry farming - costs
    De doelstelling van het onderzoek is om de waardevermindering van met Salmonella enteritidis (S.e.) en Salmonella typhymurium (S.t.) besmet pluimveevlees van vleeskuikens te bepalen. Hoe hoog is de opbrengstenderving en hoe hoog zijn de extra kosten van maatregelen voor de slachterij of uitsnijderij? Wat is de waardevermindering van levende vleeskuikens in de situatie dat de slachterij de schade doorberekent aan de vleeskuikenhouder vanaf het moment dat dieren besmet zijn bij het stalonderzoek?
    In vitro and in vivo virulence of Salmonella Typhimurium DT104: a parallelogram approach
    Berk, P.A. - \ 2008
    Wageningen University. Promotor(en): Tjakko Abee; Marcel Zwietering, co-promotor(en): R. Jonge. - [S.l. : S.n. - ISBN 9789085049340 - 167
    salmonella typhimurium - virulentie - zuren - weerstand - stressreactie - antibioticaresistentie - salmonella typhimurium - virulence - acids - resistance - stress response - antibiotic resistance
    Salmonella is present in different food products. In this research it is concluded that Salmonella, which can survive the stomach of humans better (acid resistant bacteria), have a higher probability of causing an infection than Salmonella strains that are less able to survive the stomach (acid sensitive bacteria). The probability of such an infection is determined using different model systems. Effects on an infection with cultured human and rat intestinal cells were comparable to results obtained with a rat model. The probability of infection calculated with the results from both model systems agree with data from human experiments conducted in the fifties and with epidemiological dose response data. If these results can be founded by additional research, with different Salmonella species, it could be possible to reduce the amount of animal experiments in the future.
    Influence of temperature fluctuations on Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium in manure.
    Semenov, A.V. ; Bruggen, A.H.C. van; Overbeek, L.S. van; Termorshuizen, A.J. ; Semenov, A.M. - \ 2007
    FEMS microbiology ecology 60 (2007)3. - ISSN 0168-6496 - p. 419 - 428.
    stalmest - escherichia coli - salmonella typhimurium - temperatuur - temperatuurresistentie - pathogenen - voedselveiligheid - gastro-enteritis - voedselvergiftiging - farmyard manure - escherichia coli - salmonella typhimurium - temperature - temperature resistance - pathogens - food safety - gastroenteritis - food poisoning - green fluorescent protein - aggregative behavior - nitrogen-content - bovine manure - united-states - amended soil - survival - growth - cattle
    The effects of four average temperatures (7, 16, 23 and 33°C) and daily oscillations with three amplitudes (0, ±4, ±7°C) on the survival of the enteropathogens Escherichia coli O157:H7 and Salmonella serovar Typhimurium were investigated in small microcosms. Manure was inoculated with a green fluorescent protein transformed strain of either pathogen at 107 cells g¿1 dry weight. Samples were collected immediately after inoculation, and 1 and 2 weeks after inoculation for E. coli O157:H7, and immediately and after 2 and 3 weeks for Salmonella serovar Typhimurium. Population densities were determined by dilution plating and direct counting. In addition, total bacterial CFUs were determined. Growth and survival data were fitted to a modified logistic model. Analysis of the estimated parameter values showed that E. coli O157:H7 survived for shorter periods of time and was more sensitive to competition by the native microbial community than Salmonella serovar Typhimurium. Survival of both pathogens significantly declined with increasing mean temperatures and with increasing amplitude in daily temperature oscillations. The results indicated that responses of enteropathogens to fluctuating temperatures cannot be deduced from temperature relationships determined under constant temperatures.
    Ecology and risk assessment of E. coli O157:H7 and Salmonella typhimurium in the primary production chain of lettuce
    Franz, E. - \ 2007
    Wageningen University. Promotor(en): Ariena van Bruggen, co-promotor(en): Aad Termorshuizen. - [S.l.] : S.n. - ISBN 9789085047285 - 216
    lactuca sativa - slasoorten - voedselbesmetting - escherichia coli - salmonella typhimurium - stalmest - risicofactoren - microbiële ecologie - bodem - biologische landbouw - biologische voedingsmiddelen - primaire productie - lactuca sativa - lettuces - food contamination - escherichia coli - salmonella typhimurium - farmyard manure - risk factors - microbial ecology - soil - organic farming - organic foods - primary production
    Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratorysimulated lettuce production chain. Dairy cows were fed 3 different roughage types: high digestible grass silage + maize silage (6:4), low digestible grass silage and straw. Each was adjusted with supplemental concentrates to a high and low crude protein level. The pathogens were added to manure which was subsequently mixed (after 56 and 28 d for resp. E. coli O157:H7 and Salmonella serovar Typhimurium) with 2 pairs of organically and conventionally managed loamy and sandy soil. After another 14 d, iceberg-lettuce seedlings were planted and checked for pathogens after 21 d of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157: H7 in soil). Roughage type significantly influenced the decline rate of E. coli O157: H7 in manure with the fastest decline in manure from the pure straw diet and the slowest in manure from the grass-silage + maize-silage diet. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw compared to the manure from the grass-silage + maize-silage diet. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic compared to conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.
    Stress response and virulence in Salmonella Typhimurium: a genomics approach
    Hermans, A.P.H.M. - \ 2007
    Wageningen University. Promotor(en): Tjakko Abee; Marcel Zwietering, co-promotor(en): H.J.M. Aarts. - [S.l.] : S.n. - ISBN 9789085045724 - 180
    salmonella typhimurium - stressreactie - virulentie - bacteriofagen - transcriptie - genexpressieanalyse - salmonella typhimurium - stress response - virulence - bacteriophages - transcription - genomics
    Since 1995 the number of human infections with Salmonella serovar Typhimurium DT104 increased in The Netherlands and abroad. The multi antibiotic resistance of this strain has been often proposed as plausible reason for this increase. Within his PhD research, Armand Hermans found novel DT104 specific DNA, that is most likely involved in virulence and might be an additional reason for the DT104 increase. In addition, the possibility for DT104 to survive certain process- and product conditions has been studied in this genomics based research. A better survival of stress such as acid or heat treatment could be another additional explanation for the DT104 increase. To enlarge the current insights on this topic, the activities of stress survival and virulence genes were studied by using the microarray technology. During exposure of DT104 to different stresses, similar stress survival mechanisms were activated, while different virulence mechanisms were stress specific activated. Bacterial cell communication also may play a role in regulation of these genes.
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