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See detailThe French language runs throughout the world
Morato, Nicola ULg; Gaunt, Simon

E-print/Working paper (2015)

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See detailDevelopping competencies of public managers: a hybrid system analysis in a critical management education perspective
Göransson, Marie; Rondeaux, Giseline ULg

Conference (2015, July)

The role and competencies of public managers are a central topic of public administration reforms implemented these last 30 years in OECD countries. In fact, as New Public Management (NPM) doctrines ... [more ▼]

The role and competencies of public managers are a central topic of public administration reforms implemented these last 30 years in OECD countries. In fact, as New Public Management (NPM) doctrines suggest, public administration managers have to be professionalized and free to manage (Minogue, Hulme & Polidano, 1998). This professionalization and managerial freedom imply the development of new competencies borrowed from the private sector. This leads public managers to be focused on the search for performance and to consider citizens as clients. Without losing its dominance, the NPM conception has evolved with the development of new theoretical paradigms such as Neo-Weberian State (Pollitt & Bouckaert, 2004 ; Peters, 2001 ; Drechsler, 2005) and Public Value Management (Stoker, 2006 ; Moore, 1995). In these models, the manager is still driven by performance targets to provide citizen-customers professional and quality service. However, these paradigms reassert the centrality of the State and the specificity of the public sector by comparison with the private sector. In addition, the public manager must play a role in the co-construction of public value for citizens and political actor in both the short and long term (Greve, 2010). These evolutions have led to a need for hiring public managers with new profiles, and this has been reflected in new practices for recruiting and training future top civil servants. In Belgium, at some levels of government, these practices include for instance mandatory training prior to the appointment of public managers. This training aims at developing the managerial skills of the Walloon and French-speaking public services leaders. Doing so, the purpose is to guarantee the objectification of public managers’ nomination. But so far, do these trainings develop the skills highlighted by the theoretical models above? Are they in line with the ambitions of public management reforms of the last thirty years? From these first questions, we analyse on the one hand the training system genesis and the interactions between the original actors, and on the other hand, the effects of the training, in a critical perspective. Our study of the training effects is critical for two reasons. First, it questions the role of training in the transmission of the dominant principles conveyed by the NPM and its successors. Second, it considers the role of this training in the reproduction of power games between actors. In other words, we analyse how the compulsory training actually reflects a new conception of public managers and their competencies. Moreover, we consider the impact of this training on the political-administrative system and the power relations included. To this end, we articulate two distinctive approaches: one inspired by the strategic analysis (Crozier & Friedberg, 1977) to understand the interactions between actors at the genesis of the dispositive; and the other one inspired by Critical Management Education (CME), emphasizing the role of management training in the transmission of dominant ideology (Caproni & Arias, 1997). [less ▲]

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See detailIdentification of the main parameters controlling the plasticity of ceramic pastes: The case study of the Marrakech region (Morocco)
El Idrissi, Hicham; Fontaine, François ULg

Poster (2015, July)

Numerous traditional ceramic workshops occur within a range of 10 to 80 km around the city of Marrakech. Our study aims to identify the main parameters controlling the plasticity of pastes used by the ... [more ▼]

Numerous traditional ceramic workshops occur within a range of 10 to 80 km around the city of Marrakech. Our study aims to identify the main parameters controlling the plasticity of pastes used by the artisans. To reach this goal, we characterize by X-ray diffraction, granulometry and plasticity index (PI) the local raw clayey material. The investigation of 26 whole pastes shows the dominance of quartz (20 to 50%) and clay minerals (25 to 60%) with K-feldspar (2 to 17%), plagioclase (2 to 25%), calcite (0 to 18%), dolomite (0 to 15%), goethite (0 to7%) and trace of hematite and anhydrite (< 3%). Amphibole occurs in trace (< 5%) but only in some samples. The clay minerals are diversified, including illite (10 to 40%), kaolinite (2 to 15%), mixed-layer (ML) (0 to 10%), smectite, vermiculite and chlorite (0 to 5%), and pyrophyllite-talc association (0 to 8%). Sepiolite (12%) is only present in one paste. The grain size is made by variable proportions of sand (5 to 65%), silt (12 to 53%) and clayey fraction (18 to 66%). The Plasticity index (PI) indicates the presence of two principals groups of pastes. (1) The first group is characterized by PI values ranging between 15 to 18. Their moderate plasticity behavior is related either to the low rate of clayey fraction and/or to the absence of plastic clays like smectites and mixed layer with smectitic sheets. (2) The PI of second group ranges between 20 to 32. The high plasticity values are influenced by the presence of specific clayey minerals like talc-pyrophyllite or sepiolite, or by the high content of smectite plus smectitic mixed-layers within the clayey (< 2 micron) fraction. Only one sample without any of these plastic minerals but with a high content of clayey fraction is characterized by a high PI value (24). We concluded that the workability of ceramic paste in Marrakech region is controlled by a combination of factors, dominated by the grain size distribution and the content in plastic clay minerals within the fine fraction. [less ▲]

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See detailFlora and fauna from a new Famennian (Upper Devonian) locality at Becco, eastern Belgium
Olive, Sébastien; Clément, Gaël; Denayer, Julien ULg et al

in Geologica Belgica (2015), 18(2-4), 92-101

The Becco locality (Liège province), belongs to the Theux tectonic window and represents a proximal, probably fluvial, environment corresponding to a channel infill. We present here a preliminary report ... [more ▼]

The Becco locality (Liège province), belongs to the Theux tectonic window and represents a proximal, probably fluvial, environment corresponding to a channel infill. We present here a preliminary report of the fossil assemblage discovered at the locality. The Becco site has yielded a diverse flora of early seed plants including Moresnetia zalesskyi, Dorinnotheca streeli and Condrusia sp. This assemblage, characteristic of the Belgian Famennian, highlights the diversity of early spermatophytes in the country. Becco has also delivered a rich vertebrate fauna with antiarch, groenlandaspid and phyllolepid placoderms, diplacanthiform acanthodians, as well as actinopterygians and various sarcopterygians. The fossiliferous assemblage of Becco resembles those of several Devonian tetrapod- bearing localities, including that of Strud in Belgium, and could therefore provide a favorable palaeoecological setting in the search for early tetrapods. [less ▲]

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See detailModifications acoustiques de la voix d’enseignantes au cours de la journée et de l’année scolaire
Remacle, Angélique ULg; David, Claire; Petillon, Caroline et al

Conference (2015, June 30)

Introduction Les enseignants font partie des professionnels de la voix, définis comme des travailleurs qui ne peuvent se passer de leur voix dans l’exercice de leur profession, et qui à ce titre ... [more ▼]

Introduction Les enseignants font partie des professionnels de la voix, définis comme des travailleurs qui ne peuvent se passer de leur voix dans l’exercice de leur profession, et qui à ce titre nécessitent une qualité de vocale constante (1). Cette population est particulièrement à risque et constitue le groupe de travailleurs le plus nombreux à consulter les ORL pour cause de dysphonie (2). Dans ce contexte, la recherche tente d’identifier les indices acoustiques de la fatigue vocale dans le but d’améliorer le dépistage précoce des problèmes de voix, leur traitement et leur prévention. Cette étude menée in situ a pour objectif de mettre en évidence des modifications acoustiques et prosodiques consécutives à 1) une journée de travail et 2) cinq mois de travail en milieu scolaire. Méthode La population est constituée de 22 enseignantes du primaire ayant moins de 5 années d’expérience. Pour chaque participante, cinq /a/ tenus ainsi que la lecture d’un texte ont été enregistrés 1) à deux moments de la journée de travail, soit au matin et au soir, et 2) à trois temps de l’année, soit en octobre (T0), en décembre (T1) et en février (T2). Sur les voyelles tenues, nous avons mesuré le temps maximum phonatoire (TMP), la fréquence moyenne, le jitter, le shimmer, et le rapport harmoniques/bruit (HNR). Sur les textes, nous avons mesuré la fréquence moyenne, la variation de fréquence et d’intensité (écart-type), ainsi que des paramètres relatifs au débit de parole (nombre de syllabes par seconde, nombre de pauses et durée moyenne des pauses). Pour chaque paramètre, une ANOVA en mesure répétées (2 moments * 3 temps) a été réalisée. Résultats L’effet principal du moment montre une augmentation de la fréquence moyenne mesurée sur les voyelles et sur le texte suite à une journée de travail (p<.01). Parallèlement, le TMP et le HNR augmentent (p<.01), tandis que le jitter et le shimmer diminuent en fin de journée (p<.05). Les mesures de débit montrent que les enseignantes tendent à faire moins de pauses lors de la lecture de texte en fin de journée, et que ces pauses sont de plus courte durée (p<.05). L’effet principal du temps montre une augmentation de la fréquence moyenne des voyelles et du texte au cours de l’année (p<.01), avec des valeurs plus élevées observées en décembre (T1). Les mesures relatives au débit montrent également une augmentation du nombre de syllabes par seconde (p<.01) et une tendance des locutrices à faire moins de pauses. Conclusion L’évolution des paramètres observés suggère une augmentation de la fatigue vocale et un comportement phonatoire davantage hyperfonctionnel au cours de la journée et au cours de l’année. Les résultats montrent une dégradation vocale majorée au mois de décembre, en comparaison avec les autres moments de l’année. Bibliographie 1.Titze IR, Lemke J, Montequin D. Populations in the U.S. workforce who rely on voice as a primary tool of trade: A preliminary report. Journal of Voice. 1997;11(3):254-259. 2. Remacle, A., Petitfils, C., Lejeune, L., Finck, C., & Morsomme, D. Quel est le profil professionnel des patients consultant en phoniatrie ? 70e Congrès de la Société Française de Phoniatrie, Paris, France. (13 octobre 2014). [less ▲]

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See detailAsymmetric limit cycle oscillations in systems with symmetric freeplay
Dimitriadis, Grigorios ULg

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics, IFASD 2015 (2015, June 30)

In this paper, a simple 2D aeroelastic system with degrees of freedom in pitch, plunge and control surface deflection is investigated with freeplay in the pitch degree of freedom. It is shown that this ... [more ▼]

In this paper, a simple 2D aeroelastic system with degrees of freedom in pitch, plunge and control surface deflection is investigated with freeplay in the pitch degree of freedom. It is shown that this system features a fixed point at the origin as well as two anti-symmetric fixed points. Asymmetric limit cycles that span only two of the three piecewise linear subdomains of the phase plane can orbit these anti-symmetric fixed points. A single three-domain symmetric cycle and two two-domain cycles appear as a result of a grazing bifurcation occurring at the flutter speed of the underlying linear system. The two-domain cycles can undergo further fold, period doubling and torus bifurcations. They can cause both periodic and aperiodic oscillations, including highly chaotic responses at parameter values where they interact strongly. [less ▲]

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See detailCould alternative solanaceous hosts act as refuges for the tomato leafminer, Tuta absoluta?
Bawin, Thomas ULg; Dujeu, David ULg; De Backer, Lara ULg et al

in Arthropod-Plant Interactions (2015), 9(4), 425-435

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a widespread devastating pest reported to develop on economically important solanaceous plants. The characterization of its effective ... [more ▼]

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a widespread devastating pest reported to develop on economically important solanaceous plants. The characterization of its effective host range could help to understand and prevent the dispersion behavior of the insect in the environment. In this study, the ability of T. absoluta to locate and develop on wild (Solanum nigrum, Atropa belladonna, Datura stramonium) and cultivated (Solanum tuberosum) solanaceous plant species under laboratory conditions was assessed. Dual-choice behavioral assays performed in flying tunnels (S. tuberosum versus another plant) revealed that adult distribution and female oviposition did not differ between Solanum species, which were preferred to the other tested plants. The volatile molecules released by each tested plant species provide some explanations in the observed behavioral discrimination: S. nigrum and S. tuberosum volatile profiles were similar, and were presenting quantitative and qualitative differences with the other tested Solanaceous plants. To determine whether the host plant choice was adaptive or not, we have finally conducted fitness assays, by rearing T. absoluta larvae on each plant species and have shown that Solanum species allowed higher larval survivability and lower development time (from egg to adult emergency) compared to the other plants. We conclude that Solanum species are suitable host plants for T. absoluta, but other Solanaceous plant species could be opportunistically colonized with fewer incidences. [less ▲]

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See detailLe lecteur de Barthes : jouisseur du judas ?
Lorent, Fanny ULg

Conference (2015, June 30)

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See detailExploiting Interspecific Genetic Variability for Improving Common bean for higher productivity on soils presenting biotic and abiotic stresses
Butare, Louis ULg

Doctoral thesis (2015)

Biotic and abiotic stresses often occur in the same field of rural poor farmer households in tropical countries resulting in heavy losses of common bean yields. To improve resistance of common beans ... [more ▼]

Biotic and abiotic stresses often occur in the same field of rural poor farmer households in tropical countries resulting in heavy losses of common bean yields. To improve resistance of common beans, sensitive Phaseolus vulgaris (SER16) was crossed to resistant P. coccineus (G35346-3Q) to create 94 F5:6 recombinant inbred lines (RILs) of the pedigree SER16♀ x (SER16♀ x G35346-3Q♂). The objectives of this study were to (i) identify potential parents for resistance to Al, drought and Fusarium root rot among 11 bean genotypes, (ii) to evaluate 94 F5:6 Recombinant Inbred Lines (RILs) of the cross SER 16♀ x (SER 16♀ x G35346-3Q♂) both for their resistance to Al and /or drought, (iii) to evaluate RILs for resistance to Fusarium root rot, and (iv) to identify QTL for resistance to these stresses. RILs were characterized in greenhouse for resistance to Al using a hydroponic screening employing a nutrient solution with or without 20 μM Al , to Al-toxic acid soil with high Al (HAl) and low Al (LAl) saturation, to terminal drought simulation with and without progressive soil drying, to combined stresses of Al and terminal drought in 80 cm long soil cylinder system, and to Fusarium root rot using inoculated perlite soil and sand (2:1). Two field studies were also carried on in Colombia under rainfed and irrigated conditions in Palmira, and high Al saturated acid soil in Santander of Quilichao. Our studies confirmed the superiority in Al response of Andean common beans in greenhouse trials compared to Middle American type for several root traits. Each screening method of our Al greenhouse experiments permitted an evaluation of different aspects of root traits. The two parents were virtually equal for tap root elongation rate at 24 h in the 20 μM Al treatment at about 1.4 mm h-1 while progenies ranged from less than 1-1.75 mm h-1. The correlation between leaf area and total root length was highly significant under high Al saturation (r = 0.70***) for HAl-acid soil. Two genotypes (ALB88 and ALB 91) emerged as strong multiple trait lines for the two abiotic stresses. Fusarium root rot induced root growth inhibition as high as 80.8% for the susceptible ALB 5, while resistant RILs (ALB45, ALB41, ALB126, ALB84, ALB49, ALB34, ALB88 and ALB85) didn`t show any inhibition . Seed yield under drought stress conditions was positively associated to 100-seed weight both under irrigated field (r = 0.28**) and rainfed field (r = 0.36***), and negatively associated to days to maturity (DTM) (r = - 0.36***) in field evaluation in Al-toxic acid soil in Quilichao (Colombia). QTLs for important traits including root characteristics under high Al , grain yield and yield components for drought and high Al saturation soil were identified. The use of both soil and hydroponic system, and field could contribute to evaluation of breeding materials to identify genotypes that combine Al resistance with acid soil tolerance, drought and root rot tolerance. [less ▲]

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See detailERT to monitor the bioremediation of hydrocarbons with Rhodococcus erythropolis T902.1 at a pilot scale
Masy, Thibaut ULg; Caterina, David; Tromme, Olivier et al

Conference (2015, June 30)

Petroleum hydrocarbons (HC) represent the most widespread contaminants in the world and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the ... [more ▼]

Petroleum hydrocarbons (HC) represent the most widespread contaminants in the world and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the efficiency of such a technique (by biostimulation or bioaugmentation) strongly depends on numerous environmental characteristics (heterogeneities of the subsurface structure, soil moisture, oxygen and pollutants bioavailability, microbial niches…) and is still difficult to predict a priori. In order to lower these uncertainties, Electrical Resistivity Tomography (ERT) appears as a valuable non-invasive tool to detect soil heterogeneities and to monitor biodegradation. The main objective of this study was thus to isolate with ERT an electrical signature corresponding to an enhanced biodegrading activity, in an aged HC-contaminated clay loam soil. To achieve it, a pilot tank with metric dimensions (3.6 × 0.9 × 0.6 m) and a recirculating system (which is quite unique for this type of purpose) was built to mimic field conditions and to control the evolution of the bio-physico-chemical parameters (microbial concentration in soil and groundwater, temperature, pH, pO2, redox potential, bulk and fluid conductivities, water flow, hydrocarbon content) through time and space. Five panels of electrodes were placed at different locations in the tank to detect lithological heterogeneities and to monitor the bulk resistivity variations with time-lapse ERT. Compared to a first insufficient biostimulation phase with H2O2 and KNO3, bioaugmentation with Rhodococcus erythropolis T902.1 led to a HC depletion of almost 80% (6900 to 1600 ppm) in 3 months in the center of the contaminated clay, where pollutants were less bioavailable. Furthermore, lithological heterogeneities (clay, sand, gravels) and microbial activities (growth, degradation and biosurfactant production) were successfully discriminated by ERT images obtained during both remediation phases. In the future, this cost-effective technique should be transferred to the field in order to either (i) detect and forecast biodegradation processes before choosing an appropriate remediation technique, or (ii) monitor the efficiency of this biodegradation during an in-situ bioremediation. [less ▲]

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See detailMetal bioavailability and bioaccumulation in the polychaete Nereis virens (Sars): the effects of site-specific sediment characteristics
Pini, Jennifer; Richir, Jonathan ULg; Watson, Gordon

in Marine Pollution Bulletin (2015), 95(2), 565575

The present study investigates the relationships between copper (Cu) and zinc (Zn) concentrations in sediment, pore water and their bioaccumulation in the polychaete Nereis (Alitta) virens, as well as the ... [more ▼]

The present study investigates the relationships between copper (Cu) and zinc (Zn) concentrations in sediment, pore water and their bioaccumulation in the polychaete Nereis (Alitta) virens, as well as the importance of site-specific sediment characteristics in that process. Sediment, pore water and N. virens were sampled from seven sites with different pollution histories along the English Channel coast. Results showed that site-specific metal levels and sediment characteristics were important in determining the bioavailability of metals to worms. Significant correlations were found between Cu in the sediment and in the pore water and between Zn in the pore water and in N. virens. Zn from the pore water was thus more readily available from a dissolved source to N. virens than Cu. Data also showed that metal concentrations in N. virens were lower than those found in other closely related polychaetes, indicating that it may regulate tissue concentrations of Cu and Zn. [less ▲]

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See detailUsing 2D-PIV measurements to compute unsteady aerodynamic loads on a flat plate at high angle of attack
Guissart, Amandine ULg; Bernal, Luis; Dimitriadis, Grigorios ULg et al

in Proceedings of the 16th International Forum on Aeroelasticity and Structural Dynamics, IFASD 2015 (2015, June 30)

This work exposes and discusses results obtained for aerodynamic forces using an indirect calculation based on Particle Image Velocimetry (PIV) measurements. The methodology used is based on the integral ... [more ▼]

This work exposes and discusses results obtained for aerodynamic forces using an indirect calculation based on Particle Image Velocimetry (PIV) measurements. The methodology used is based on the integral formulation of the Navier-Stokes equations and is applied to spatio-temporal data for different flows around a plate with a 16:1 chord-to-thickness ratio at high angle of attack. Experimental data are obtained in a water channel for both a static and a pitching plate. In addition to PIV data, direct measurements of aerodynamic loads are carried out to assess the quality of the indirect calculation. It is demonstrated that this indirect method is able to compute the mean and the temporal evolution of the lift and drag coefficients with a reasonable accuracy. It is also shown that the noise sensitivity of the method can be partly alleviated through the use of Dynamic Mode Decomposition (DMD) as a pre-processing step to smooth the spatio-temporal data. [less ▲]

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See detailA comparative study for simulation of heat transport in large district heating network
Sartor, Kevin ULg; Thomas, David ULg; Dewallef, Pierre ULg

in Prooceedings of ECOS 2015 (2015, June 29)

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See detailUnsteady Viscous-Inviscid Coupling Simulations of Separated Laminar Flows Around 2D Airfoils
Rothkegel Ide, José Ignacio ULg; Dimitriadis, Grigorios ULg

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics, IFASD 2015 (2015, June 29)

An interactive boundary layer model has been developed in 2D in order to solve the unsteady flow around an airfoil. The inviscid problem is solved using a panel method, by the discretization of the ... [more ▼]

An interactive boundary layer model has been developed in 2D in order to solve the unsteady flow around an airfoil. The inviscid problem is solved using a panel method, by the discretization of the airfoil into linear-varying vortex panels. The solution of the boundary layer equations is carried out using a finite volume scheme. Viscous-inviscid coupling is preformed by imposing a permeation velocity on the skin panels of the airfoil and the addition of a free wake at each separation point. [less ▲]

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See detailTheoretical and experimental investigation of a structurally and aerodynamically nonlinear pitch and flap wing
Verstraelen, Edouard ULg; Boutet, Johan ULg; Grappasonni, Chiara ULg et al

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics, IFASD 2015 (2015, June 29)

This paper presents and experimental and theoretical investigation of a novel nonlinear aeroelastic system. It consists of a wing with pitch and flap degrees of freedom, suspended from a leaf spring ... [more ▼]

This paper presents and experimental and theoretical investigation of a novel nonlinear aeroelastic system. It consists of a wing with pitch and flap degrees of freedom, suspended from a leaf spring secured in a nonlinear clamp. Both the structural and the aerodynamic forces acting on the wing can be nonlinear, depending on the amplitude of oscillations. Wind tunnel experiments show that the system undergoes a supercritical Hopf bifurcation that leads to small amplitude limit cycle oscillations. At a particular airspeed, the pitch amplitude jumps to a much higher value and dynamic stall starts to occur. Three mathematical models of the system are formulated, one based on linear aerodynamics and two based on the Leishman-Beddoes dynamic stall model. The objective of the modelling is to determine whether the jump in pitch oscillation amplitude is due to dynamic stall. The predictions for amplitude, frequency and mean angle of the limit cycle oscillations are compared to the experimental observations. All three models predict the small amplitude oscillations with satisfactory accuracy. The complete Leishman-Beddoes model predicts the occurrence of a jump in pitch amplitude but the magnitude of this jump is signi cantly overestimated. The other two models completely fail to model the jump. The failure of the Leishman-Beddoes model to predict the correct post-jump oscillation amplitude may be due to the values selected for the model parameters. [less ▲]

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See detailBilan bactériologique des mammites dans les troupeaux Zébu Azawak à la station expérimentale sahélienne de Toukounous (Niger) et épidémiologie moléculaire des Staphylococcus aureus isolés entre 2009 et 2012
Issa Ibrahim, Abdoulkarim ULg

Doctoral thesis (2015)

L’élevage est la seconde activité principale après l’agriculture au Niger. Cependant, ce secteur est confronté à d’énormes problèmes, notamment la faible productivité des animaux, le faible investissement ... [more ▼]

L’élevage est la seconde activité principale après l’agriculture au Niger. Cependant, ce secteur est confronté à d’énormes problèmes, notamment la faible productivité des animaux, le faible investissement, des problèmes d’alimentation et d’accès aux points d’eau, et divers problèmes sanitaires récurrents. Depuis l’indépendance du pays en 1960, plusieurs politiques ont été mises en œuvre pour améliorer la productivité des espèces et races domestiques locales. C’est ainsi que, la station expérimentale sahélienne de Toukounous a vu le jour, avec comme objectifs la sélection et la diffusion de la race Zébu Azawak auprès des producteurs ruraux. Les efforts de sélection ont abouti à l’obtention d’un animal standard bien adapté au contexte sahélien avec un niveau de production en lait acceptable. Le bétail laitier à travers le monde souffre énormément des problèmes sanitaires liés aux infections de la glande mammaire. La situation est la même à Toukounous malgré la proximité de services vétérinaires et para-vétérinaires. Cependant, au Niger de manière générale, les données sur les mammites sont rares et très peu de publications scientifiques sont disponibles. Une des possibles explications est la prévalence élevée de mammites sub-cliniques, mais faible de mammites cliniques. La présente étude est dès lors centrée sur les problèmes de mammites au sein de la station sahélienne expérimentale de Toukounous afin d’identifier : (i) les vaches souffrant de mammites cliniques et/ou subcliniques ; (ii) les principales bactéries pathogènes responsables ; et (iii) les virulotypes et profils de résistance aux antibiotiques des souches de Staphylococcus (S.) aureus isolées ; et afin de démontrer l’impact positif de l’application de mesures simples d’hygiène lors de la traite manuelle sur la prévalence de vaches avec mammite. De 2009 à 2012, l’ensemble des vaches en lactation des trois troupeaux de la station, à savoir « élites », « non-élites » et « primipares » ont été testées avec le « California Mastitis Test » (CMT). Ensuite, le lait de tous les quartiers des vaches ayant réagi positivement au test CMT a été prélevé pour réaliser des analyses bactériologiques au Niger. Les espèces bactériennes pré-identifiées au Niger ont ensuite été importées en Belgique (ULg-FMV) afin de procéder à une identification complète par des galeries API®. Les souches confirmées de S. aureus ont par la suite été étudiées pour leurs virulotypes (i) phénotypiquement pour la production de biofilm par mesure de la densité optique après croissance en milieu liquide en plaque de microtitration et pour la synthèse d’une capsule par un test ELISA ; et (ii) génétiquement par PCR ciblant des gènes codant pour différentes propriétés de virulence (adhésines, leucotoxines, entérotoxines, biofilm, et capsule) ; ainsi que pour leurs profils de résistance aux antibiotiques par le test de diffusion en gélose, ou antibiogramme. Ces mêmes souches ont été comparées par leurs empreintes génétiques après « Pulsed Field Gel Electrophoresis » (PFGE), ou pulsotypes, pour en étudier la clonalité au cours des 4 années de l’enquête et dans les 3 troupeaux. Enfin, l’impact de mesures d’hygiène (lavage et désinfection du pis, des trayons et des mains des trayeurs avant et/ou après chaque traite) a été évalué en 2011 et en 2012, en comparant la prévalence de vaches positives au test CMT et l’identité des bactéries isolées en présence ou en absence de ces mesures. Au cours de la première étude en 2009 sur la prévalence des vaches positives au test CMT et l’identité des bactéries mammopathogènes, 104 des 265 vaches (39%) testées dans l’ensemble des 3 troupeaux étaient positives au test CMT, bien qu’aucune mammite clinique n’ait été diagnostiquée. Les analyses bactériologiques ont identifié 55 souches bactériennes: la moitié (51%) appartient au genre Staphylococcus, essentiellement à l’espèce S. aureus (42%). Les autres bactéries identifiées appartiennent à la famille des Enterobacteriaceae (26%) et aux genres Enterococcus (13%), Bacillus (9%) et Acinetobacter (2%). Des résultats similaires ont été obtenus en 2010, 2011 et 2012, bien que les pourcentages respectifs puissent varier selon l’année et le troupeau. Les résultats des tests phénotypiques et génétiques du virulotypage (études 1 et 3) des 122 souches de S. aureus isolées de 2009 à 2012 dans les trois troupeaux n’ont permis d’effectuer aucun regroupement. Par contre, les résultats des empreintes génétiques par PFGE sur ces mêmes souches ont montré qu’elles appartiennent à 16 pulsotypes différents, dont trois sont plus fréquents, A (33%), D (23%) et B (21%). Ces différents pulsotypes se distinguent, dans une certaine mesure, par la présence plus fréquentes des gènes icaA, spa et cap5H dans les souches des pulsotypes A et B ; des gènes cap8H, seg, sei et seb dans celles du pulsotype D ; et du gène luks-PV dans celles des pulsotypes B et D. Pour ce qui concerne les antibiogrammes des mêmes 122 souches (études 1 et 2 + résultats non publiés), des pourcentages élevés de souches résistantes de S. aureus, particulièrement aux -lactamines, ont été relevés. Ainsi, 41% des souches testées étaient résistantes à la pénicilline et 7%, à l’oxacilline. Mais, aucune souche résistante à la méticilline (SARM) ne possède le gène mecA. Les pourcentages de souches résistantes atteignaient 11% pour la tétracycline et la gentamicine, mais restaient inférieurs à 5% pour la clindamycine, l’association trimétoprime-sulfaméthoxazole et l’enrofloxacine. Pour la 4ème étude en 2011 et 2012, les mesures d’hygiène ont été appliquées pendant 6 mois : lavage du pis avant la traite, trempage des trayons avec de la chlorhexidine après la traite, et lavage et désinfection des mains des trayeurs avec une solution antiseptique à base d’hypochlorite de sodium. L’application de ces mesures a diminué de manière statistiquement significative les pourcentages de vaches positives au test CMT en comparaison avec les résultats dans les troupeaux et au cours des années sans application de ces mêmes mesures d’hygiène. En 2012, par exemple, les pourcentages de vaches positives au CMT dans les troupeaux « élite » et « non-élite » ont diminué de 65% et 62%, à 44% et 41% après trois mois d’application, puis à 20% et 24% après 6 mois d’application, respectivement. Par contre, ces mesures d’hygiène n’ont eu aucun effet statistiquement significatif sur les pourcentages relatifs des différents pathogènes identifiés. En conclusion, les mammites bovines sévissent essentiellement sous forme sub-clinique à la station sahélienne de Toukounous. Le genre Staphylococcus et l’espèce S. aureus sont les bactéries mammopathogènes les plus fréquemment identifiées. Les souches de S. aureus appartiennent à différents virulotypes et pulsotypes, bien que trois de ces derniers soient plus fréquents dans les trois troupeaux et au cours des quatre années de l’étude. Ces mêmes souches présentent différents profils de résistance aux antibiotiques, avec près de la moitié d’entre elles résistantes à des membres de la famille de -lactames. Enfin, l’application de mesures d’hygiène (lavage et désinfection du pis, des trayons et des mains des trayeurs) avant et/ou après la traite manuelle permet de réduire la prévalence des vaches positives au test CMT de manière statistiquement significative, mais n’a pas d’influence sur les fréquences relatives des bactéries pathogènes identifiées dans les laits. [less ▲]

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See detailTrajectory optimization for 3D robots with elastic links
Lismonde, Arthur ULg; Sonneville, Valentin ULg; Bruls, Olivier ULg

Scientific conference (2015, June 29)

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