Septic arthritis has the potential to be a highly destructive joint disease. Although numerous bacterial species are capable of inducing septic arthritis, Staphylococcus aureus is most commonly implicated, accounting for up to 65% of cases. Whilst this organism is known to produce a diverse array of potential virulence factors, studies investigating a variety of S. aureus-related infections have implicated alpha(Hla)-, beta(Hlb)- and gamma(Hlg)-haemolysins as key damaging toxins, with the ‘pore-forming’ Hla considered to be the most potent. The work presented in this study focused on gaining further insight into the interaction between S. aureus toxins and in situ chondrocytes during an episode of septic arthritis. An in vitro bovine osteochondral explant model of S. aureus-induced septic arthritis was developed in this study. Utilising fluorescence-mode confocal laser scanning microscopy (CLSM), the model, which avoided the complexities of a host immune response, permitted an assessment of the following: (1) the spatial and temporal quantification of in situ chondrocyte viability following exposure to both a laboratory ‘wild-type’ (S. aureus 8325-4) and clinical strains of S. aureus; (2) the influence of Hla, Hlb and Hlg on in situ chondrocyte viability through the use of specific ‘haemolysin-knockout’ mutant strains; (3) the influence of altered culture medium osmolarity and extracellular Ca2+ on Hla-induced in situ chondrocyte death; and (4) dynamic changes in intracellular Ca2+ within in situ chondrocytes following Hla exposure. S. aureus 8325-4 and S. aureus clinical strains rapidly reduced in situ chondrocyte viability ( > 45% chondrocyte death at 40hrs). The increased acidity, observed during bacterial culture, had a minimal effect on chondrocyte viability. Chondrocyte death commenced within the superficial zone (SZ) of cartilage and rapidly progressed to the deep zone (DZ). Simultaneous exposure of SZ and DZ chondrocytes to S. aureus 8325-4 toxins (achieved with the use of subchondral bone-free explants) demonstrated that SZ chondrocytes were more susceptible to the toxins than DZ chondrocytes. When explants were cultured in the presence of a selection of isogenic S. aureus mutants, with varying Hla, Hlb and Hlg production capabilities (all originating from S. aureus 8325-4), Hla-producing mutants induced significant in situ chondrocyte death compared to toxin deficient controls (Hla-Hlb-Hlg-). In contrast, mutants producing Hlb and Hlg in the absence of Hla were unable to induce significant chondrocyte death. Hla alone was therefore identified as the key damaging toxin to in situ chondrocyte viability. Raised culture medium osmolarity had no influence on Hla-induced in situ chondrocyte death. In the absence of Hla, a high extracellular Ca2+ concentration (20mM) had no influence on chondrocyte viability during the experimental period. Hla-induced chondrocyte death increased in the presence of raised extracellular Ca2+ concentrations thereby confirming a role of Ca2+ in the chondrocyte death pathway. There was no significant difference between S. aureus growth in high and low Ca2+ culture media. Finally, when live osteochondral explants stained with the Ca2+-sensitive fluorophore Fluo-4 were cultured with an Hla-containing S. aureus supernatant (S. aureus 8325-4 (Hla+Hlb+Hlg+)) there was a significant rise in intracellular Ca2+ in comparison to those explants exposed to a non-Hla-containing supernatant (S. aureus DU5938 (Hla- Hlb-Hlg-)). The Hla-induced Ca2+ transients were always followed by chondrocyte death. Thus, it is likely that Hla-induced chondrocyte death was associated with a rise in intracellular Ca2+. These findings are of translational relevance. Firstly, toxins released by S. aureus have a rapid and fatal action on in situ chondrocytes, thereby advocating the prompt and thorough removal of bacteria and their toxins during the treatment of septic arthritis. Secondly, the identification of Hla alone as the key damaging toxin to in situ chondrocyte viability, with its destructive action being associated with a rise in intracellular Ca2+, may enable the development of future targeted therapeutic strategies in order to reduce the extent of cartilage destruction during and after an episode of septic arthritis.

Bacterial infection within a joint, septic arthritis, is a serious condition in horses that can lead to long-term joint disease if the infection is not resolved quickly. Equine septic arthritis is diagnosed primarily based on clinical signs and synovial fluid cytology. Septic synovial fluid is characterized by significant elevations in total protein (TP) and total nucleated cell count (TNCC). However, in some cases it can be difficult to distinguish between septic arthritis and non-septic joint inflammation (synovitis) based on clinical signs and synovial fluid cytology alone. A rapid assay to help confirm septic arthritis would be advantageous. A new assay to quantify the major equine acute phase protein, serum amyloid A (SAA) may fulfill this need. Serum amyloid A increases in the body in response to injury, infection, and inflammation and shows promise as a useful tool in confirming a diagnosis of sepsis, as inflammation causes mild increases in SAA and infection causes marked elevations. In our study, serial serum and synovial fluid samples were collected from horses with experimental models of synovitis and septic arthritis, synovial fluid cytology was performed, and serum and synovial fluid SAA were quantified. Synovial fluid TNCC and TP concentrations increased significantly following induction of both models. Serum and synovial fluid SAA concentrations remained normal in synovitis horses and increased significantly in septic arthritis horses. Any elevation in serum or synovial fluid SAA above normal values may be supportive of synovial sepsis since synovial inflammation alone did not result in SAA elevations in our model. / Master of Science

This research evaluated serum amyloid A (SAA) concentration in synovial fluid of healthy horses as a potential marker for use in the diagnosis and monitoring of horses with septic arthritis. The first study evaluated the effect of arthroscopic lavage of healthy joints on concentrations of systemic and synovial SAA; as well as total protein concentration, nucleated cell count and percentage of neutrophils in synovial fluid. The second study, evaluated the effect of repeated through-and-through joint lavage on SAA in systemic blood and SAA, total protein, nucleated cell count and percentage of neutrophils in synovial fluid from healthy joints. In the first study, middle carpal joints of 6 horses were randomly assigned to one of the following treatments 1) arthrocentesis (controls) or 2) arthroscopic lavage. A washout period of 30 days was allowed in between treatments. Synovial fluid and blood samples were collected at 0, 24, 48, 72, 96 and 120 h. Measurements included SAA in blood and synovial fluid, and total protein, nucleated cell count and percentages of neutrophils in synovial fluid. In the second study, one tarsocrural joint was randomly assigned to receive repeated through-and-through joint lavage at 0, 48 and 96 h in 6 horses. Synovial fluid and blood samples were collected at 0, 24, 48, 72, 96 and 120 h. Measurements included SAA in blood and synovial fluid, and total protein, nucleated cell count and percentages of neutrophils in synovial fluid. For this study, synovial fluid samples collected at time 0 were considered as control values. After arthroscopic lavage and repeated through-and-through joint lavage, systemic and synovial SAA did not increase from baseline values (except for systemic SAA at 24h after arthroscopic lavage and in controls). Total protein values were significantly increased at all time points after arthroscopic and through-and-through joint lavages (except at 96h on both lavage procedures) but not in controls. With both lavage procedures, nucleated cell count significantly increased from baseline values at all time points (except at 96h after through-and-through joint lavage). Percentage of neutrophils was significantly increased after arthroscopic lavage at all time points and only at 24h in controls; however, the percentages of neutrophils were not significantly increased after repeated through-and-through joint lavage. Synovial SAA was not affected by arthroscopic or repeated through-and-through joint lavage; however, synovial total protein and nucleated cell counts were significantly increased. Synovial SAA may be a valuable inflammatory marker that is not affected by procedures as arthroscopic or repeated through-and-through joint lavage in horses. Further validation of synovial SAA as a marker for evaluating the progression of septic joints while treatment is installed is warranted.

No description available.

En bakteriell ledinfektion kallas för septisk artrit och utan snabb behandling kan tillståndet leda till irreversibla ledskador och flera allvarliga komplikationer. Snabb diagnostik är viktigt för en god prognos och med nuvarande metod för odling av ledvätska tar det upp till fem dygn för detektion av mikroorganismer. Metoden inkluderar odling på fasta substrat och i blododlingsflaskor. Med en ny metod som använder multiplex PCR (polymerase chain reaction) skulle analystiden kunna minskas till en timme. BioFire Joint Infection (JI) Panel är ett test som kan detektera flera mikroorganismer samtidigt genom amplifiering av DNA. Mikroorganismer detekteras och identifieras genom cellysering, DNA-rening, PCR-reaktioner i två steg och smältanalys. Syftet med arbetet var att utvärdera BioFire JI Panel för detektion av mikroorganismer i ledvätska och jämföra metodens känslighet med standardiserad odling respektive odling i buljong, och svara på frågeställningen hur känslig JI-panelen är jämfört med standardiserad odlingsmetod. Prov konstruerades genom att suspendera målbakterierna Staphylococcus aureus, Escherichia coli, Streptococcus pyogenes, Neisseria gonorrhoeae, Haemophilus influenzae, Kingella kingae och Finegoldia magna i natriumklorid. Suspensionerna seriespäddes och odlades ut på fasta substrat, inokulerades i blododlingsflaskor och buljonger samt analyserades med JI-panelen för att identifiera metodernas detektionsgränser. Fasta substrat, blododlingsflaskor och buljonger visade likvärdig känslighet för majoriteten av bakterieisolaten medan JI-panelen generellt visade en sämre eller likvärdig känslighet i jämförelse med standardmetod. Panelen visade potential för detektion av svårodlade bakterier och skulle vara ett bra komplement till nuvarande odlingsmetod. Ytterligare studier hade behövts men den snabba analystiden som möjliggör snabbare behandling framhävde metodens kliniska potential. / Bacterial joint infections are called septic arthritis and without rapid diagnosis and treatment the condition could lead to irreversible joint damage and other serious complications. With the current method for synovial fluid cultivation, which includes both solid substrates and culture vials, detection of microorganisms takes up to five days. With a new method utilizing multiplex polymerase chain reaction (PCR), the time to detection could decrease to an hour. BioFire Joint Infection (JI) Panel can detect multiple microorganisms simultaneously through amplification of DNA. Microorganisms are detected and identified by cell lysis, DNA purification and two consecutive PCR reactions with subsequent melting curve analysis. The aim of the study was to evaluate the BioFire JI Panel for detection of microorganisms in synovial fluid and compare the method’s sensitivity to standard and broth cultivation. Samples were constructed by suspending target bacteria, Staphylococcus aureus, Escherichia coli, Streptococcus pyogenes, Neisseria gonorrhoeae, Haemophilus influenzae, Kingella kingae and Finegoldia magna, in sodium chloride. The suspensions were serially diluted and cultivated on solid substrates, in culture vials, broth and analyzed with the JI panel to find the detection limits for each method. Solid substrates, culture vials and broth exhibited similar sensitivity while the JI panel generally had a lower or similar sensitivity compared to standard methods. The panel showed potential detecting difficult to grow bacteria and would be a good complement to current methods. Further studies are required but the quick analysis enabling faster treatment highlighted the clinical potential.

L’arthrite septique chez les bovins est une affection le plus souvent d’origine bactérienne qui est une cause de boiterie fréquente associée à des pertes économiques importantes. Le traitement, qui doit être initié le plus rapidement possible, s’appuie sur l’utilisation combinée d’anti-inflammatoires non stéroïdiens, d’un ou de plusieurs lavages articulaires ainsi que d’antibiotiques administrés de façon systémique pour un minimum de 3 semaines. Cette durée d’administration constitue une difficulté pour les élevages dits biologiques pour lesquels un cahier des charges strict limite un recours prolongé aux antibiotiques. Ainsi le traitement efficace de diverses conditions infectieuses et celui de l’arthrite septique en particulier dans ces élevages peut être compromis. L’objectif de ce travail est de s’appuyer sur les propriétés antimicrobiennes des solutions de saline hypertonique (SSH) pour limiter l’utilisation des antibiotiques dans les cas d’arthrite septique chez les veaux en intégrant ces solutions pour le lavage des articulations infectées. Notre première étude a consisté à déterminer la sécurité d’emploi de deux concentrations de SSH (une commerciale à 7.2% et une maison à 15%) dans des articulations supposées saines chez le veau. Une synovite sévère associée à des signes cliniques caractéristiques d’atteintes articulaires a été observé lors de l’utilisation de SSH 15%. Son utilisation clinique comme solution de lavage articulaire est par conséquent déconseillée. Concernant la SSH 7.2%, malgré une synovite d’intensité variable, nous n’avons pas noté des signes cliniques caractéristiques d’atteintes articulaires. Son utilisation dans un contexte expérimental d’infection articulaire nous a paru réaliste. Notre seconde étude a permis d’évaluer les effets du lavage articulaire avec de la SSH 7.2% dans un modèle expérimental d’infection à Escherichia coli. Trois groupes de traitement ont été constitués. Dans le premier groupe (traitement standard), un lavage était effectué avec du lactate de Ringer (LRS) et les veaux recevaient une administration biquotidienne de ceftiofur par voie intraveineuse pour 21 jours. Dans le deuxième groupe (LRS), un lavage était effectué avec du LRS et aucun antibiotique n’était administré. Enfin dans le troisième groupe (SSH), un lavage était effectué avec de la SSH 7.2% sans qu’aucun antibiotique ne soit administré. Tous les veaux ont reçu du kétoprofen quotidiennement pendant 3 jours. L’inoculation s’est fait au jour 1 et les traitements ont débuté au jour 2. L’efficacité des traitements a été établie sur des critères cliniques, bactériologiques et cytologiques. Dans le modèle que nous avons utilisé, les trois groupes de traitements ont conduits à une guérison clinique et bactériologique satisfaisante (absence de boiterie, de douleur et de croissance bactérienne dans le liquide articulaire en fin d’étude). La guérison cytologique n’a quant à elle pas été jugée satisfaisante avec des moyennes de comptage et de pourcentage en neutrophiles tout groupe confondu bien supérieures aux valeurs normales (11.39x109/l de neutrophiles représentant 74.73% des leucocytes en fin d’étude). Le traitement avec la SSH 7.2% s’est révélé être significativement plus traumatique et pas plus efficace dans l’élimination de l’infection comparativement au traitement LRS. D’autre part, le lavage articulaire au LRS s’est révélé être aussi efficace et sécuritaire que le traitement standard de l’arthrite septique qui incluait 21 jours de ceftiofur administré par voie intraveineuse. Ainsi, bien que le lavage avec de la SSH 7.2% n’est pas démontré de résultats satisfaisants qui permettrait de limiter le recours aux antibiotiques dans les filières biologiques, l’association d’un lavage au LRS avec le ketoprofen s’est révélée être une alternative possible. De nouvelles études sont requises pour confirmer ses résultats et pour déterminer le rôle respectif du lavage articulaire et du ketoprofen dans la guérison lors d’arthrite septique. / Septic arthritis in cattle is mainly an infectious bacteriological disease that is a frequent cause of lameness and is associated with great economic losses. Treatment must be prompt and includes non steroidal anti-inflammatory drugs with one or several joint lavage along with systemic antibiotics for at least 3 weeks. This long course of administration is unachievable for organic production systems where the use of antibiotics is strictly regulated. Thus the treatment of infectious disease with septic arthritis in particular may be jeopardized in these herds. The objectives of this work is to use antimicrobial properties of hypertonic saline solution (HSS) to limit the use of antibiotics in septic arthritis cases in calves, using HSS for joint lavage. In our first study, we assessed the safety of two HSS of different concentrations (commercial 7.2% and home-made 15%) in healthy calves joint. A severe synovitis associated with typical clinical signs of joint lesions was observed when HSS 15% was used. Therefore this solution cannot be recommended for joint lavage in calves. A synovitis of variable degree was observed when HSS 7.2% was used. However no clinical signs or joint lesions were noted. Based on these results, we felt that HSS 7.2% could be tested in an experimental setting of joint infection. In our second study, we evaluate the effects of joint lavage with HSS 7.2% in an experimental infection model with Escherichia coli. Three treatment groups were formed. In the first group, the joint lavage was realized with Lactated Ringer’s Solution (LRS) and calves also received ceftiofur intravenously two times a day for 21 days. In the second group, the joint lavage was realized with LRS and saline was used instead of ceftiofur. In the last group, the joint lavage was realized with HSS 7.2% and saline was used instead of ceftiofur. All calves in this study received ketoprofen once a day for 3 days intravenously. Inoculation of bacteria took place on day 1 and all treatments started on day 2. Treatment’s effectiveness was established upon clinical, bacteriological and cytological criteria. In our model, all treatment groups led to clinical and bacteriological recovery (no lameness, pain or positive culture in the synovial fluid at the end of the experiment). Whatever the treatment group, cytological recovery was no achieved at the end of the study with mean number and percentage of neutrophils far superior when compared to usual values (11.39x109/l of neutrophils representating 74.73% of total leucocytes at the end of the experiment). Joint lavage with HSS 7.2% combined with ketoprofen successfully treat septic arthritis in this model but was significantly more harmful compared to joint lavage with LRS combined with ketoprofen. On the other hand, joint lavage with LRS combined with ketoprofen was found as efficient and safe than the standard treatment of septic arthritis which includes a 21 day administration of intravenous ceftiofur. Therefore, even if HSS 7.2% joint lavage cannot be a good choice to treat septic with the restriction of use of antibiotics in organic herds, the combination of a LRS joint lavage with ketoprofen showed promising results. Further studies are warranted to confirm these latter results and to determine specific effects of the lavage and of ketoprofen.

A artrite séptica (AS), também chamada de artrite infecciosa, é uma doença inflamatória das articulações iniciada por um agente infeccioso. O agente causal mais comum da SA é Staphylococcus aureus (S. aureus). A patogênese da SA inclui uma resposta inflamatória complexa envolvendo sistema imune inato e adaptativo. As citocinas liberadas a partir de macrófagos, tais como TNF-?, IL-1? e IL-6, foram classicamente apontadas como os principais mediadores da inflamação grave que precede a destruição da cartilagem e osso e a disfunção articular permanente mediante a AS. A evidência radiológica está frequentemente presente, mas não diferencia o afrouxamento mecânico do septo das articulações. Portanto, se houver algum indício de suspeita de infecção, deve ser aspirado para avaliação microbiológica. Recentemente, as tecnologias de imagem como a micro tomografia computadorizada (?CT) foram amplamente utilizadas para modelos pré-clínicos de distúrbios articulares auto-imunes. No entanto, as características radiológicas da AS em camundongos ainda são amplamente desconhecidas. No estudo atual, os camundongos NMRI foram inoculados intravenosamente ou intra-articularmente com a cepas de S. aureus Newman ou LS-1. Os sinais radiológicos e clínicos da artrite séptica foram acompanhados durante 10 dias usando ?CT. Avaliamos as correlações entre alterações radiológicas conjuntas e sinais clínicos, alterações histológicas e níveis séricos de citocinas. Nos dias 5-7 após a infecção intravenosa, a destruição óssea verificada por ?CT tornou-se evidente na maioria das articulações infectadas. Os sinais radiológicos de destruição óssea eram dependentes da dose bacteriana. O local mais comumente afetado pela artrite séptica foi o fêmur distal nos joelhos. A destruição óssea detectada pelo ?CT foi correlacionada positivamente com alterações histológicas na artrite séptica local e hematogênica. Os níveis séricos de IL-6 foram significativamente correlacionados com a gravidade da destruição das articulações. Coletivamente, nossos dados mostram que o ?CT é um método sensível para monitorar a progressão da doença e determinar a gravidade da destruição óssea em um modelo de artrite séptica do mouse; enquanto que a IL-6 é um potencial biomarcador de destruição óssea na artrite séptica. / Extracellular vesicles (EVs) are heterogeneous population of nano- and micro-sized vesicles secreted from almost every cell type. The process of EV secretion seems to be evolutionary conserved across the species kingdoms, ranging from simple prokaryotes to higher eukaryotes including bacteria, viruses, and parasitic protozoa such as leishmania and malarial parasites, fungi, plants and animals. Recent data suggests that Staphylococcus aureus (S. aureus) bacteria secretes EVs that could mediate host-pathogen interactions. EVs have been investigated in various bacterial species which modulate the secretion of immunoregulatory molecules such as cytokines and may have key role in infection. However, their role in S. aureus septic arthritis has not been explored yet. In current study, we postulate novel perspectives for the implementation of S. aureus-derived EVs in vitro as well as in vivo model of septic arthritis. EVs derived from S. aureus were applied to stimulate mice splenocytes in vitro as well as intra-articularly and the cytokine levels were measured. Our results showed that S. aureus derived EVs potentially provoke the production of proinflammatory cytokines. TNF-?, and IL-6 were significantly elevated in splenocytes in vitro after EV-based stimulation. Moreover, NMRI mice were injected with variable doses of EVs intraarticularly and mice were observed for 10 days to examine inflammation and development of septic arthritis. Bone and cartilage destruction was assessed by histochemistry analysis to score the joint erosion. Altogether, our results demonstrate the putative role of S. aureus-derived EVs in provoking inflammation and immunological responses suggesting that these vesicles could induce and disseminate systemic immune response during the development of septic arthritis.

A artrite séptica (AS), também chamada de artrite infecciosa, é uma doença inflamatória das articulações iniciada por um agente infeccioso. O agente causal mais comum da SA é Staphylococcus aureus (S. aureus). A patogênese da SA inclui uma resposta inflamatória complexa envolvendo sistema imune inato e adaptativo. As citocinas liberadas a partir de macrófagos, tais como TNF-?, IL-1? e IL-6, foram classicamente apontadas como os principais mediadores da inflamação grave que precede a destruição da cartilagem e osso e a disfunção articular permanente mediante a AS. A evidência radiológica está frequentemente presente, mas não diferencia o afrouxamento mecânico do septo das articulações. Portanto, se houver algum indício de suspeita de infecção, deve ser aspirado para avaliação microbiológica. Recentemente, as tecnologias de imagem como a micro tomografia computadorizada (?CT) foram amplamente utilizadas para modelos pré-clínicos de distúrbios articulares auto-imunes. No entanto, as características radiológicas da AS em camundongos ainda são amplamente desconhecidas. No estudo atual, os camundongos NMRI foram inoculados intravenosamente ou intra-articularmente com a cepas de S. aureus Newman ou LS-1. Os sinais radiológicos e clínicos da artrite séptica foram acompanhados durante 10 dias usando ?CT. Avaliamos as correlações entre alterações radiológicas conjuntas e sinais clínicos, alterações histológicas e níveis séricos de citocinas. Nos dias 5-7 após a infecção intravenosa, a destruição óssea verificada por ?CT tornou-se evidente na maioria das articulações infectadas. Os sinais radiológicos de destruição óssea eram dependentes da dose bacteriana. O local mais comumente afetado pela artrite séptica foi o fêmur distal nos joelhos. A destruição óssea detectada pelo ?CT foi correlacionada positivamente com alterações histológicas na artrite séptica local e hematogênica. Os níveis séricos de IL-6 foram significativamente correlacionados com a gravidade da destruição das articulações. Coletivamente, nossos dados mostram que o ?CT é um método sensível para monitorar a progressão da doença e determinar a gravidade da destruição óssea em um modelo de artrite séptica do mouse; enquanto que a IL-6 é um potencial biomarcador de destruição óssea na artrite séptica. / Extracellular vesicles (EVs) are heterogeneous population of nano- and micro-sized vesicles secreted from almost every cell type. The process of EV secretion seems to be evolutionary conserved across the species kingdoms, ranging from simple prokaryotes to higher eukaryotes including bacteria, viruses, and parasitic protozoa such as leishmania and malarial parasites, fungi, plants and animals. Recent data suggests that Staphylococcus aureus (S. aureus) bacteria secretes EVs that could mediate host-pathogen interactions. EVs have been investigated in various bacterial species which modulate the secretion of immunoregulatory molecules such as cytokines and may have key role in infection. However, their role in S. aureus septic arthritis has not been explored yet. In current study, we postulate novel perspectives for the implementation of S. aureus-derived EVs in vitro as well as in vivo model of septic arthritis. EVs derived from S. aureus were applied to stimulate mice splenocytes in vitro as well as intra-articularly and the cytokine levels were measured. Our results showed that S. aureus derived EVs potentially provoke the production of proinflammatory cytokines. TNF-?, and IL-6 were significantly elevated in splenocytes in vitro after EV-based stimulation. Moreover, NMRI mice were injected with variable doses of EVs intraarticularly and mice were observed for 10 days to examine inflammation and development of septic arthritis. Bone and cartilage destruction was assessed by histochemistry analysis to score the joint erosion. Altogether, our results demonstrate the putative role of S. aureus-derived EVs in provoking inflammation and immunological responses suggesting that these vesicles could induce and disseminate systemic immune response during the development of septic arthritis.

L’arthrite septique chez les bovins est une affection le plus souvent d’origine bactérienne qui est une cause de boiterie fréquente associée à des pertes économiques importantes. Le traitement, qui doit être initié le plus rapidement possible, s’appuie sur l’utilisation combinée d’anti-inflammatoires non stéroïdiens, d’un ou de plusieurs lavages articulaires ainsi que d’antibiotiques administrés de façon systémique pour un minimum de 3 semaines. Cette durée d’administration constitue une difficulté pour les élevages dits biologiques pour lesquels un cahier des charges strict limite un recours prolongé aux antibiotiques. Ainsi le traitement efficace de diverses conditions infectieuses et celui de l’arthrite septique en particulier dans ces élevages peut être compromis. L’objectif de ce travail est de s’appuyer sur les propriétés antimicrobiennes des solutions de saline hypertonique (SSH) pour limiter l’utilisation des antibiotiques dans les cas d’arthrite septique chez les veaux en intégrant ces solutions pour le lavage des articulations infectées. Notre première étude a consisté à déterminer la sécurité d’emploi de deux concentrations de SSH (une commerciale à 7.2% et une maison à 15%) dans des articulations supposées saines chez le veau. Une synovite sévère associée à des signes cliniques caractéristiques d’atteintes articulaires a été observé lors de l’utilisation de SSH 15%. Son utilisation clinique comme solution de lavage articulaire est par conséquent déconseillée. Concernant la SSH 7.2%, malgré une synovite d’intensité variable, nous n’avons pas noté des signes cliniques caractéristiques d’atteintes articulaires. Son utilisation dans un contexte expérimental d’infection articulaire nous a paru réaliste. Notre seconde étude a permis d’évaluer les effets du lavage articulaire avec de la SSH 7.2% dans un modèle expérimental d’infection à Escherichia coli. Trois groupes de traitement ont été constitués. Dans le premier groupe (traitement standard), un lavage était effectué avec du lactate de Ringer (LRS) et les veaux recevaient une administration biquotidienne de ceftiofur par voie intraveineuse pour 21 jours. Dans le deuxième groupe (LRS), un lavage était effectué avec du LRS et aucun antibiotique n’était administré. Enfin dans le troisième groupe (SSH), un lavage était effectué avec de la SSH 7.2% sans qu’aucun antibiotique ne soit administré. Tous les veaux ont reçu du kétoprofen quotidiennement pendant 3 jours. L’inoculation s’est fait au jour 1 et les traitements ont débuté au jour 2. L’efficacité des traitements a été établie sur des critères cliniques, bactériologiques et cytologiques. Dans le modèle que nous avons utilisé, les trois groupes de traitements ont conduits à une guérison clinique et bactériologique satisfaisante (absence de boiterie, de douleur et de croissance bactérienne dans le liquide articulaire en fin d’étude). La guérison cytologique n’a quant à elle pas été jugée satisfaisante avec des moyennes de comptage et de pourcentage en neutrophiles tout groupe confondu bien supérieures aux valeurs normales (11.39x109/l de neutrophiles représentant 74.73% des leucocytes en fin d’étude). Le traitement avec la SSH 7.2% s’est révélé être significativement plus traumatique et pas plus efficace dans l’élimination de l’infection comparativement au traitement LRS. D’autre part, le lavage articulaire au LRS s’est révélé être aussi efficace et sécuritaire que le traitement standard de l’arthrite septique qui incluait 21 jours de ceftiofur administré par voie intraveineuse. Ainsi, bien que le lavage avec de la SSH 7.2% n’est pas démontré de résultats satisfaisants qui permettrait de limiter le recours aux antibiotiques dans les filières biologiques, l’association d’un lavage au LRS avec le ketoprofen s’est révélée être une alternative possible. De nouvelles études sont requises pour confirmer ses résultats et pour déterminer le rôle respectif du lavage articulaire et du ketoprofen dans la guérison lors d’arthrite septique. / Septic arthritis in cattle is mainly an infectious bacteriological disease that is a frequent cause of lameness and is associated with great economic losses. Treatment must be prompt and includes non steroidal anti-inflammatory drugs with one or several joint lavage along with systemic antibiotics for at least 3 weeks. This long course of administration is unachievable for organic production systems where the use of antibiotics is strictly regulated. Thus the treatment of infectious disease with septic arthritis in particular may be jeopardized in these herds. The objectives of this work is to use antimicrobial properties of hypertonic saline solution (HSS) to limit the use of antibiotics in septic arthritis cases in calves, using HSS for joint lavage. In our first study, we assessed the safety of two HSS of different concentrations (commercial 7.2% and home-made 15%) in healthy calves joint. A severe synovitis associated with typical clinical signs of joint lesions was observed when HSS 15% was used. Therefore this solution cannot be recommended for joint lavage in calves. A synovitis of variable degree was observed when HSS 7.2% was used. However no clinical signs or joint lesions were noted. Based on these results, we felt that HSS 7.2% could be tested in an experimental setting of joint infection. In our second study, we evaluate the effects of joint lavage with HSS 7.2% in an experimental infection model with Escherichia coli. Three treatment groups were formed. In the first group, the joint lavage was realized with Lactated Ringer’s Solution (LRS) and calves also received ceftiofur intravenously two times a day for 21 days. In the second group, the joint lavage was realized with LRS and saline was used instead of ceftiofur. In the last group, the joint lavage was realized with HSS 7.2% and saline was used instead of ceftiofur. All calves in this study received ketoprofen once a day for 3 days intravenously. Inoculation of bacteria took place on day 1 and all treatments started on day 2. Treatment’s effectiveness was established upon clinical, bacteriological and cytological criteria. In our model, all treatment groups led to clinical and bacteriological recovery (no lameness, pain or positive culture in the synovial fluid at the end of the experiment). Whatever the treatment group, cytological recovery was no achieved at the end of the study with mean number and percentage of neutrophils far superior when compared to usual values (11.39x109/l of neutrophils representating 74.73% of total leucocytes at the end of the experiment). Joint lavage with HSS 7.2% combined with ketoprofen successfully treat septic arthritis in this model but was significantly more harmful compared to joint lavage with LRS combined with ketoprofen. On the other hand, joint lavage with LRS combined with ketoprofen was found as efficient and safe than the standard treatment of septic arthritis which includes a 21 day administration of intravenous ceftiofur. Therefore, even if HSS 7.2% joint lavage cannot be a good choice to treat septic with the restriction of use of antibiotics in organic herds, the combination of a LRS joint lavage with ketoprofen showed promising results. Further studies are warranted to confirm these latter results and to determine specific effects of the lavage and of ketoprofen.