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See detailNon destructive testing by digital shearography using a Savart plate
Michel, Fabrice ULg; Blain, Pascal ULg; Renotte, Yvon ULg et al

Poster (2009)

Shearography is a growing optical technique in the field of non-destructive testing (NDT). Hololab developed an out of plane, in line and almost common path interferometer based on polarization states ... [more ▼]

Shearography is a growing optical technique in the field of non-destructive testing (NDT). Hololab developed an out of plane, in line and almost common path interferometer based on polarization states separation using a coated prism for digital phase-shifting shearography. This setup is efficient but does not allow varying the shearing direction, that is an important parameter for defects detection and quantification. To overcome this disadvantage, the coated prism is substituted by a Savart plate device that allows scanning several shearing directions by rotating the device around the light propagation axis. Many advantages of the prism substitution are discussed. The behaviour of the Savart plate as a shearing device is experimentally analyzed to optimize its integration within the interferometer. Recorded phasemaps in NDT for different shearing directions are presented. [less ▲]

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See detailCreutzfeldt-jakob, Parkinson, lewy body dementia and Alzheimer diseases: from diagnosis to therapy.
Dupiereux-Fettweis, Ingrid ULg; Zorzi, Willy ULg; Quadrio, Isabelle et al

in Central Nervous System Agents in Medicinal Chemistry (2009), 9(1), 2-11

Depositions of proteins in form of amyloid and non-amyloid plaques are common pathogenic signs of more than 20 degenerative diseases affecting the central nervous system or a variety of peripheral tissues ... [more ▼]

Depositions of proteins in form of amyloid and non-amyloid plaques are common pathogenic signs of more than 20 degenerative diseases affecting the central nervous system or a variety of peripheral tissues. Among the neuropathological conditions, Alzheimer's, Parkinson's and the prion diseases, such as Creutzfeldt-Jakob disease (CJD), present ambiguities as regarding their differential diagnosis. At present, their diagnosis must be confirmed by post-mortem examination of the brain. Currently the ante-mortem diagnosis is still based on the integration of multiple data (clinical, paraclinical and biological analyses) because no unique marker exists for such diseases. The detection of specific biomarkers would be useful to develop a differential diagnostic, distinguishing not only different neurodegenerative diseases but also the disease from the non-pathological effects of aging. Several neurodegenerative biomarkers are present at very low levels during the early stages of the disease development and their ultra-low detection is needed for early diagnosis, which should permit more effective therapeutic interventions, before the disease concerned can progress to a stage where considerable damage to the brain has already occurred. In the case of prion diseases, there are concerns regarding not only patient care, but the wider community too, with regard to the risk of transmission of prions, especially during blood transfusion, for which, four cases of variant CJD infection associated with transfusion of non-leukocyte-depleted blood components have been confirmed. Therefore the development of techniques with high sensitivity and specificity represent the major challenge in the field of the protein misfolding diseases. In this paper we review the current analytical and/or biochemical diagnostic technologies used mainly in prion, but also in Alzheimer and Parkinson diseases and emphasizing work on the protein detection as a surrogates and specific biomarker in the body fluid of patients (urine, CSF and blood). This review highlights the urgency of the development of early and sensitive diagnostics in terms of therapeutic challenge. [less ▲]

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See detailDetection and Correction of Outliers for Fatty Acids Contents Measured by Mid-Infrared Spectrometry Using Random Regression Test-Day Models
Soyeurt, Hélène ULg; Dardenne, Pierre; Gengler, Nicolas ULg

in Book of Abstracts of the 60th Annual Meeting of the European Association for Animal Production (2009)

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See detailCarbon cycling in the mixolimnion of Lake Kivu (East Africa)
Borges, Alberto ULg; Descy, J.-P.; Delille, Bruno ULg et al

Poster (2009)

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See detailDecoherence, entanglement and irreversibility in quantum dynamical systems with few degrees of freedom
Jacquod, Ph; Petitjean, Cyril ULg

in Advances in Physics (2009), 58(2), 67-196

In this review we summarize and amplify recent investigations of coupled quantum dynamical systems with few degrees of freedom in the short-wavelength, semiclassical limit. Focusing on the correspondence ... [more ▼]

In this review we summarize and amplify recent investigations of coupled quantum dynamical systems with few degrees of freedom in the short-wavelength, semiclassical limit. Focusing on the correspondence between quantum and classical physics, we mathematically formulate and attempt to answer three fundamental questions. (i) How can one drive a small dynamical quantum system to behave classically? (ii) What determines the rate at which two single-particle quantum-mechanical subsystems become entangled when they interact? (iii) How does irreversibility occur in quantum systems with few degrees of freedom? These three questions are posed in the context of the quantum-classical correspondence for dynamical systems with few degrees of freedom, and we accordingly rely on two short-wavelength approximations to quantum mechanics to answer them: the trajectory-based semiclassical approach on the one hand, and random matrix theory on the other hand. We construct novel investigative procedures towards decoherence and the emergence of classicality out of quantumness in dynamical systems coupled to external degrees of freedom. In particular, we show how dynamical properties of chaotic classical systems, such as local exponential instability in phase space, also affects their quantum counterparts. For instance, it is often the case that the fidelity with which a quantum state is reconstructed after an imperfect time-reversal operation decays with the Lyapunov exponent of the corresponding classical dynamics. For related reasons, but perhaps more surprisingly, the rate at which two interacting quantum subsystems become entangled can also be governed by the subsystem's Lyapunov exponents. Our method allows us to differentiate quantum coherent effects (those related to phase interferences) from classical ones (those related to the necessarily extended envelope of quantal wavefunctions) at each stage in our investigations. This makes it clear that all occurrences of Lyapunov exponents we witness have a classical origin, although they require rather strong decoherence effects to be observed. We extensively rely on numerical experiments to illustrate our findings and briefly comment on possible extensions to more complex problems involving environments with many interacting dynamical systems, going beyond the uncoupled harmonic oscillators model of Caldeira and Leggett. [less ▲]

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See detailFactors influencing microbiological and chemical composition of South-Belgian raw sludge
Guillemet, Thibault A.; Maesen, Philippe ULg; Delcarte, Emile et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2009), 13(2), 249-255

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See detailTwo parent magmas for the same anorthosite pluton? The Egersund-0gna case
Duchesne, Jean Clair; Charlier, Bernard ULg; Vander Auwera, Jacqueline ULg

in EOS : Transactions, American Geophysical Union (2009), 90(22), 11-02

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See detailAnalyse expérimentale du fonctionnement hydraulique des déversoirs en touches de piano
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Actes du Colloque Dimensionnement et Fonctionnement des Evacuateurs de crues (2009)

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See detailAdvances in quality control for dioxins monitoring and evaluation of measurement uncertainty from quality control data.
Eppe, Gauthier ULg; De Pauw, Edwin ULg

in Journal of Chromatography. B : Analytical Technologies in the Biomedical & Life Sciences (2009), 877

This paper describes an application of multivariate and multilevel quality control charts with the aim of improving the internal quality control (IQC) procedures for the monitoring of dioxins and dioxin ... [more ▼]

This paper describes an application of multivariate and multilevel quality control charts with the aim of improving the internal quality control (IQC) procedures for the monitoring of dioxins and dioxin-like PCBs analysis in food. Dioxin analysts have to use the toxic equivalent concept (TEQ) to assess the toxicity potential of a mixture of dioxin-like compounds. The TEQ approach requires quantifying individually 29 dioxin-like compounds. Monitoring the congeners separately on univariate QC charts is misleading owing to the increase of false alarm rate. We propose to subdivide the TEQ value into 3 sub-groups and to control simultaneously the 3 variables in a T(2) chart. When a T(2) exceeds the upper control limit, it acts as a warning to trigger additional investigations on individual congeners. We discuss the minimum number of runs required to reliably estimate the QC chart parameters and we suggest using data from multilevel QC charts to properly characterize the standard deviations and the correlation coefficients. Moreover, the univariate QC chart can be sensitised to detect systematic errors by using exponentially weighted moving average (EWMA) technique. The EWMA chart provides an additional guidance on setting appropriate criteria to control the method bias and to support trend analysis. Finally, we present an estimate of measurement uncertainty by computing the accuracy profile in a retrospective way with the QC data generated and we discuss assessment of compliance with regulatory maximum levels. [less ▲]

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See detailPCDD/Fs and dioxin-like PCBs in home-produced eggs from Belgium: levels, contamination sources and health risks.
Van Overmeire, I.; Waegeneers, N.; Sioen, I. et al

in Science of the Total Environment (2009), 407(15), 4419-29

This paper discusses the dioxin TEQ levels as determined by the chemically activated luciferase gene expression assay (CALUX) and by HRGC-HRMS in eggs, soils, faeces and kitchen waste samples obtained in ... [more ▼]

This paper discusses the dioxin TEQ levels as determined by the chemically activated luciferase gene expression assay (CALUX) and by HRGC-HRMS in eggs, soils, faeces and kitchen waste samples obtained in the CONTEGG study. The samples were collected in each Belgian province at private homes and in small gardens where chickens are held. The CALUX levels for eggs sampled in autumn were higher than the levels in eggs obtained at the same locations in spring (median values of 5.86 and 4.08 pg CALUX TEQ/g fat, respectively). The total WHO-TEQ levels in eggs, determined by HRGC-HRMS, ranged from 3.29 to 95.35 pg TEQ/g fat in autumn and from 1.50 to 64.79 pg TEQ/g fat in spring. In the soils on which the chickens forage, levels of 2.51-11.35 pg I-TEQ/g in autumn and 2.00-7.86 pg I-TEQ/g in spring were found. The congener pattern of PCDD/Fs in the eggs, soils and faeces was dominated by OCDD, in addition to 1,2,3,4,6,7,8-HeptaCDD, OCDF and 1,2,3,4,6,7,8-HeptaCDF. The predominant dioxin-like PCBs were PCB118, PCB 105 and PCB 156. The dioxin-like PCBs contributed on average 47%, 14% and 20% to the total WHO-TEQ in eggs, soils and faeces, respectively. Kitchen waste samples were very low-contaminated with dioxin-like compounds. The present results showed a good agreement between egg and soil TEQ levels for PCDD/Fs but not for dioxin-like PCBs. This study showed that current soil levels found in some private gardens do not lead to egg levels below the current EU maximal level of 6 pg total TEQ/g fat for dioxins and dioxin-like PCBs. The consumers of the analysed eggs attained 5-79% of the tolerable weekly intake (TWI) of 14 pg TEQ/kg bw for dioxins and dioxin-like PCBs by exposure to their home-produced eggs only. [less ▲]

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See detailEffects of aggressive encounters on plasma corticosteroid-binding globulin and its ligands in white-crowned sparrows.
Charlier, Thierry ULg; Underhill, Caroline; Hammond, Geoffrey L. et al

in Hormones & Behavior (2009), 56(3), 339-47

In birds, corticosteroid-binding globulin (CBG) binds corticosterone, progesterone and testosterone. The concentration of each ligand can alter the binding of the other ligands through competitive ... [more ▼]

In birds, corticosteroid-binding globulin (CBG) binds corticosterone, progesterone and testosterone. The concentration of each ligand can alter the binding of the other ligands through competitive interactions. Thus, an increase in corticosterone or progesterone may displace testosterone bound to CBG, leading to an increase in bioactive free testosterone levels without affecting total testosterone levels in the circulation. Aggressive interactions increase plasma total testosterone levels in some birds but not in others. Here, we tested the hypothesis that aggressive encounters in the late breeding season would not increase total testosterone levels in plasma, but would alter CBG, total corticosterone or total progesterone levels in such a way as to modify the number of available binding sites and therefore occupancy by testosterone. A marked decrease in CBG occupancy by testosterone would indirectly suggest an increase in free testosterone levels in plasma. Wild male white-crowned sparrows were exposed to a simulated territorial intrusion (STI) or control for 30 min. Subjects were then caught and bled. We measured CBG using a ligand-binding assay and corticosterone, progesterone and testosterone using highly sensitive radioimmunoassays. STI significantly increased aggressive behaviors but did not affect plasma total testosterone levels. STI significantly increased plasma CBG and total corticosterone levels and decreased plasma total progesterone levels. We predict that CBG occupancy by corticosterone will increase slightly following an aggressive encounter. However, this small change is unlikely to increase free testosterone levels, because of the large number of seemingly unoccupied CBG binding sites in these subjects. [less ▲]

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See detailDevelopment of a practical test of insulin resistance in obese Beagle dogs and effects of sc FOS
Daumas, Caroline; Lhoest, Estelle; Hornick, Jean-Luc ULg et al

in Mussa, P. P.; Nery, J.; Schiavone, A. (Eds.) et al Congress Proceedings 13t h Congress of the ESVCN (2009)

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See detailTopology Optimization of Structural Components: A Multibody Dynamics-Oriented Approach
Bruls, Olivier ULg; Lemaire, Etienne ULg; Duysinx, Pierre ULg et al

in Proceedings of the Multibody Dynamics ECCOMAS Conference (2009)

This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural ... [more ▼]

This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-static load cases to mimic the complex loadings in service. In contrast, this paper proposes an optimization procedure based on the dynamic simulation of the full multibody system with large amplitude motions and elastic deflections. We show that the simulation model, which involves a nonlinear finite element formulation, a time integration scheme and a sensitivity analysis, can be efficiently exploited in an optimization loop. The method is applied to truss structural components. Each truss is represented by a separate structural universe of beams with a topology design variable attached to each one. A SIMP model (or a variant of the power law) is used to penalize intermediate densities. The optimization formulation is stated as the minimization of the mean compliance over a time period or as the minimization of the mean tip deflection during a given trajectory, subject to a volume constraint. In order to illustrate the benefits of the integrated design approach, the case of a two degrees-of-freedom robot arm is developed. [less ▲]

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See detailTranscriptomic and proteomic analyses of seasonal photoperiodism in the pea aphid
LE TRIONNAIRE, G.; Francis, Frédéric ULg; JAUBERT-POSSAMAI, S. et al

in BMC Genomics (2009), 29

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See detailEvaluation de la qualité de vie de personnes âgées : état actuel et utilisation de l’Inventaire Systémique de Qualité de Vie (ISQV©)
Missotten, Pierre ULg; Etienne, Anne-Marie ULg; Squelard, Gilles ULg et al

in Revue Francophone de Clinique Comportementale et Cognitive (2009), 14(3), 14-21

This study approaches the question of the evolution of the quality of life (QOL) measures in older patient populations. On base of the report of the weak number of instruments specifically adapted to this ... [more ▼]

This study approaches the question of the evolution of the quality of life (QOL) measures in older patient populations. On base of the report of the weak number of instruments specifically adapted to this population and of the absence of instruments taking into account both the expectations and the priorities of the individuals, we wished to make the adaptation of a tool for adult, the Quality of life Systematic Inventory (QLSI©). In this prospect, the main aim of this preliminary research was to test the evaluative approach of the QLSI© within a population of old people and to obtain useful information for the construction of a version of the QLSI© for old people. 135 voluntary subjects, from 65 to 85 years old, living at home and having a good health participated in the study. The questionnaire revealed a good QOL which could be explained by the combination of diverse factors such as a good current situation, a lesser importance given to the diverse life domains and the relatively weak goals. The results demonstrated the relevance of the QLSI© but also showed the necessity of certain modifications to make this questionnaire more specific to the old person. [less ▲]

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See detailRegistrum omnium librorum medicinalium... La bibliothèque de Nicolas Valckenisse († ca 1480), docteur en médecine de Louvain
Adam, Renaud ULg; Van Hoorebeeck, Céline

in Vons, Jacqueline (Ed.) Pratique et pensée médicales à la Renaissance. Actes du 51e Colloque international d’études humanistes (Tours, 2-6 juillet 2007) (2009)

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See detailProviding sustainable long term care: a looming challenge
Cremer, Helmuth; De Donder, Philippe; Pestieau, Pierre ULg

in Toulouse School of Economics (2009), (3),

Long-term care (LTC hereafter) concerns people who depend on help to carry out daily activities. It is mainly delivered informally by families and to a lesser extent formally by professional care ... [more ▼]

Long-term care (LTC hereafter) concerns people who depend on help to carry out daily activities. It is mainly delivered informally by families and to a lesser extent formally by professional care assistants and nursing homes. Most EU governments are also involved in some way in the provision or financing of LTC services. Right now, the future of LTC provision appears to be gloomy, for demographic, societal and financial reasons. This TSE Note studies the strengths and weaknesses of three institutions providing LTC services - namely the family, the State and the private insurance market - and provides policy recommendations based on the view that governments should take the leadership towards a comprehensive approach of the dependency problem, while relying as much as possible on the family and the market. [less ▲]

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See detailValidation of methods for the detection of new emerging pathogenic Escherichia coli
Verstraete, K; De Reu, K; Robyn, J et al

Book published by Brussels : Belgian Science Policy (2009)

Enterohaemorrhagic Escherichia coli (EHEC) are shigatoxin producing E. coli (STEC) that can cause serious disease to humans. These food-borne pathogens belong to the fifth most common zoonoses in Belgium ... [more ▼]

Enterohaemorrhagic Escherichia coli (EHEC) are shigatoxin producing E. coli (STEC) that can cause serious disease to humans. These food-borne pathogens belong to the fifth most common zoonoses in Belgium, but due to their severe clinical symptoms in humans they are highly dreaded. They can cause a range of disease symptoms ranging from asymptomatically carriage over various diarrhoea symptoms to the life-threatening HUS (haemolytic uremic syndrome). Cattle are the main reservoir and infection of humans occurs through contact with faecal excretion material and consumption of contaminated food or water. A broad variety of serotypes is able to cause human infections, but the principal serotypes are O26, O103, O111, O145 and O157. These strains are denoted as new emerging pathogens by the WHO. The group of sorbitol non-fermenting (s-) O157:H7 strains are examined the most, because an ISO-method is available. For sorbitol fermenting (s+) O157 strains as well as for non-O157 STEC strains recently a new isolation method was developed in the Belspo project SD/AF/06A (Possé et al. 2008a). The aim of the project was the optimization and the validation of the above-mentioned detection and isolation method for STEC in different matrices. In the first place immunomagnetic separation (IMS) was evaluated for the optimization of the STEC isolation method for cattle faeces (Ghent University, UGent). Second, molecular characterization of STEC strains was performed using a newly designed 33-mPCR as an alternative tool (University of Antwerp, VIB) and pulsed field gel electrophoresis (PFGE) (Institute for Agricultural and Fisheries Research, ILVO). Also a smaller derived multiplex PCR (9-mPCR) was designed (VIB) and optimized for the screening of samples (ILVO). The third goal was the evaluation of different approaches for STEC isolation from human faecal samples (Universitair Ziekenhuis Brussel, UZ). Finally the STEC detection and isolation method was validated by an in-house and an interlaboratory study which was based on the ISO 16140 guideline for the validation of alternative methods (University of Liège; UGent; ILVO). For the optimization of the STEC isolation protocol for cattle faeces and the evaluation of the effect of IMS, cattle faecal samples were artificially inoculated with various numbers of STEC (10-100 and 100-1000 cfu/25g faeces) and isolated using the isolation protocol with 6h or 24h of enrichment followed by IMS and plating or direct plating on selective agars. Two types of IMS beads (Dynabeads and Captivate beads) were tested. Results showed that IMS (any of the two types of beads) had a highly positive effect on the isolation of serotype O157 (s- and s+), whereas only a small or even a negative effect for non-O157 serotypes was found. This was largely clarified by results on pure broth suspensions of STEC, showing that high percentages were recovered from the IMS beads used in suspensions with the serotypes O157 (s- and s+), O26 and O103, but lower percentages were recovered for O111 and O145. Non-O157 STEC were often already efficiently isolated from faeces using only direct plating, whereas O157 (s- and s+) STEC were not. For the enrichment time, 24h generally gave higher isolation efficiencies than 6h. Finally for serotypes O157 (s- and s+), O26 and O103, a level of 10-100 cfu/25g was reliably detected, whereas for serotypes O111 and O145 only 100-1000 cfu/25g was reliably detected. To accomplish the second task of the project, the Applied Molecular Genomics Group of the VIB Department of Molecular Genetics (UA-VIB) designed a proprietary 33-amplicon multiplex PCR (mPCR) assay combined with capillary electrophoresis. This mPCR assay contains the detection of 5 STEC serotypes (O26, O103, O111, O145, O157), the main virulence genes VT1 with variants (VT1ab, VT1c and VT1d), VT2 with six variants (VT2b,c,d,e,f,g) and consensus, eae with five variants (eaeα1, eaeβ1, eaeγ1; eaeγ2; eaeε and eaeζ), ehx, tir, katP, saa, espP and FliC H2, H7, H8, H11 and H28. The assay was optimized and validated on a set of test strains representative for the priority amplicons. Next, this molecular technology was validated on a collection of 334 human clinical and animal strains from the Belgian STEC Reference Center (UZ). This collection of human and animal strains was also characterized by performing the PulseNet Europe protocol for pulsed field gel electrophoresis (PFGE). This technique creates a fingerprint of a strain by means of rare cutter restriction enzyme cutting of DNA and gel electrophoresis. Analysis of the band patterns lead to clustering of strains according to similarity or relatedness. Then results of 33-mPCR and PFGE genotyping were combined to show eventual correlations between PFGE genotypes and virulence profiles. Also background information about the strains (date of isolation, human or animal source, clinical manifestation, outbreak information) was included to the analysis. Combining mPCR and PFGE genotyping results, correlations were shown. In the first place STEC strains were clustered according to their serotype. Secondly a correlation occurred between virulence profile and PFGE clustering, concerning VT genes and other genes. Particularly for STEC O157, strains had very diverse VT-profiles, and strains with the same VT-profile clustered together. Concerning the clinical manifestation, ‘asymptomatic’ cases occurred more frequently for non-O157 than for O157 STEC, but besides this no correlation was shown between the PFGE clustering and the clinical manifestation or between the VT-profile and the clinical manifestation. Finally several case studies could be appointed based on the PFGE dendrograms. In general the cases contained clones that persisted during several years, had similar virulence profiles and infected humans as well as animals. As a part of the second task, the UA-VIB also designed a derived 9-amplicon multiplex PCR (9-mPCR) for fast sample screening. Using this 9-mPCR, a combination of serotypes (O26, O103, O111, O145, O157) and virulence genes (VT1, VT2, eae and ehx) is detected in one run and can be visualized using conventional gel electrophoresis. Once the 9-mPCR was developed and tested on pure strains, an evaluation on samples was performed. Hereto ILVO (Institute for Agricultural and Fisheries Research) tested several methods to extract DNA from artificially inoculated samples. Methods were compared based on the ability to remove PCR inhibiting molecules and on the ability to isolate and purify DNA from STEC cells. Out of four methods only two methods, in which no removal of sample debris was done, were suitable for sample preparation. The method using bead beating cell lysis described by Yu and Morrison (2004), was at least 10 times more sensitive than the method using the Qiagen Stool Mini Kit according to the manufacturer’s instructions, and was therefore recommended. However, the method using bead beating cell lysis is much more time consuming than the Qiagen method and the use of a ribolyser is necessary. As ILVO used the method employing the ribolyser in all following experiments, this method was used on artificially inoculated samples to determine its detection limit. All virulence marker genes and the serotype gene of strain MB3901 (serotype O157) could be detected in enriched minced beef and cheese from raw milk artificially inoculated with 2 cfu/25g sample. For cattle fecal samples the screening test was 10 times less sensitive; 21 cfu/25g feces could be detected. Finally the influence of the volume of lysate used in the mPCR reaction mix was examined. An mPCR reaction containing 1 and 2µl of lysate DNA was performed, but no difference in detection was seen. Testing of different clinical isolates of non-O157 STEC on the newly designed selective agars, showed that growth characteristics were generally as expected. However, more standardization of the preparation of the medium is needed to obtain more reproducible results. Some O103 isolates did not grow on the media prepared at UZ and the color of the colonies of O111 was often difficult to distinguish from O26. Using artificially contaminated stool samples, the sensitivity of the STEC isolation protocol developed in a previous Belspo SPSD II project was similar to the protocol used routinely at UZ (103 and 104 cfu/5g). The sensitivity was about 10 times higher when using IMS. The method performed well on frozen STEC positive samples, but this could only be tested on 14 samples, of which 11 with O157, 2 with O111 and one O26. In-house validation of the STEC isolation protocol was performed to evaluate if the protocol is applicable for different types of food matrices. All samples used for this validation were artificially contaminated. Ten samples of minced beef, raw milk cheese and sprouted seeds were artificially inoculated with varying numbers (10-2000 cfu/25g) of non-stressed and stressed strains belonging to the serotypes O157 (s-) and (s+), O26, O103, O111 and O145. Cultured STEC strains were cold and freeze stressed by storing them for at least 5 days at respectively 2 and -18°C. Inoculated samples were pre-enriched in a weak selective medium for 6 hours followed by enrichment in a stronger selective medium for 18 hours. Direct plating on a selective medium was performed after each enrichment step. In a third pathway, an IMS (Dynabeads or Captivate beads) step was performed after 24h enrichment and prior to plating. Suspected colonies on the selective medium were purified and tentatively confirmed on a purification medium followed by a confirmation by a serotype PCR. Parallel to the classical isolation method, the 9-mPCR screening test was performed on the enrichment medium (after 24 hours enrichment). Results indicate that the isolation protocol as well as mPCR screening provide good detection of non-stressed and cold-stressed O26, O103, O157 (s+) and O145 in raw milk cheese and minced beef. Detection of the other non-stressed and cold-stressed serotypes (O111 and O157 (s+)) in raw milk cheese and minced beef and of all serotypes under freeze stressed conditions in minced beef was low or almost zero. Probably due to the high level of background flora, detection of any serotype in sprouted seeds was almost impossible even though inoculation numbers were as high as 2000 cfu/25g. Finally the optimized STEC detection and isolation methods were validated by an interlaboratory study performed by national and international laboratories (twelve laboratories in total). First, a pre-trial experiment was organized to give the collaborative laboratories the possibility to become familiar with the isolation method. Secondly, the actual interlaboratory study was performed. Products necessary to prepare all culture media (in-house-prepared: IHP) and ready-to-use selective agar culture media (ready-to-use: RTU) were sent to the participating laboratories, as well as a questionnaire and a document to report the results. For each participating laboratory, 20 samples of 25g of minced beef were prepared: one sample for the temperature measurement upon arrival, one for the enumeration of the total count, Enterobacteriaceae and E. coli, two blank samples and sixteen samples inoculated with single strains belonging to 4 serotypes at 2 levels of contamination in duplicate (30 cfu/g and 300 cfu/g). All strains were cold stressed. Samples were prepared the day of the shipment and had to be analyzed on a prefixed day. The University of Liège evaluated all results based on the recommendations of ISO 16140. Results showed no difference between RTU and IHP media. The arabinose test seemed difficult to be read, so the dulcitol test is now preferred for the confirmation of serotypes O103 and O111. Some mistakes were made during sample inoculation, like a wrong inoculation of four samples and no inoculation of one sample. If we do not take into account these mistakes, all four serotypes were detected with high sensitivity. In general it can be concluded that the laboratory performance is highly satisfactory. [less ▲]

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