Heterogeneity of Persistence of Salmonella enterica Serotype Senftenberg Strains Could Explain the Emergence of this Serotype in Poultry Flocks

Salmonella enterica serotype Senftenberg (S. Senftenberg) has recently become more frequent in poultry flocks. Moreover some strains have been implicated in severe clinical cases. To explain the causes of this emergence in farm animals, 134 S. Senftenberg isolates from hatcheries, poultry farms and human clinical cases were analyzed. Persistent and non-persistent strains were identified in chicks. The non-persistent strains disappeared from ceca a few weeks post inoculation. This lack of persistence could be related to the disappearance of this serotype from poultry farms in the past. In contrast, persistent S. Senftenberg strains induced an intestinal asymptomatic carrier state in chicks similar to S. Enteritidis, but a weaker systemic infection than S. Enteritidis in chicks and mice. An in vitro analysis showed that the low infectivity of S. Senftenberg is in part related to its low capacity to invade enterocytes and thus to translocate the intestinal barrier. The higher capacity of persistent than non-persistent strains to colonize and persist in the ceca of chickens could explain the increased persistence of S. Senftenberg in poultry flocks. This trait might thus present a human health risk as these bacteria could be present in animals before slaughter and during food processing

Conservation of Salmonella Infection Mechanisms in Plants and Animals

Salmonella virulence in animals depends on effectors injected by Type III Secretion Systems (T3SSs). In this report we demonstrate that Salmonella mutants that are unable to deliver effectors are also compromised in infection of Arabidopsis thaliana plants. Transcriptome analysis revealed that in contrast to wild type bacteria, T3SS mutants of Salmonella are compromised in suppressing highly conserved Arabidopsis genes that play a prominent role during Salmonella infection of animals. We also found that Salmonella originating from infected plants are equally virulent for human cells and mice. These results indicate a high degree of conservation in the defense and infection mechanism of animal and plant hosts during Salmonella infection

Cross-protection of Salmonella abortusovis, S. choleraesuis, S. dublin and S. gallinarum in mice induced by S. abortusovis and S. gallinarum: bacteriology and humoral immune response

Cross-protection induced by primary infection with Abortusovis and Gallinarum was examined against challenge injection with these Salmonella serotypes as well as with Dublin and Choleraesuis, the other virulent serotypes. Abortusovis induced efficient protection against the other Salmonella. Gallinarum was ineffective against Choleraesuis. Even with low multiplication in mice, the Gallinarum J91 strain induced a weak but significant protection against Dublin (same O group serotype). The antibodies in the blood of mice were tested with ELISA specific for the Salmonella antigens used to prime or to challenge animals. The Gallinarum J91 strain was detected to be more antigenic in ELISA than the other Salmonella antigens. It is difficult to conclude on a correlation between IgM or IgG antibodies and induction of protection, because of the variability in immune response according to the different serotype used. Nevertheless, the negative linkage between a number of bacteria in the spleen of mice challenged with Gallinarum and Dublin, and the level of IgM and IgG antibodies specific for the challenging serotype, showed that humoral immune response could be one element of cross-protection, mainly by the immune response against the same O serotype.Protection croisée contre Salmonella abortusovis, S. choleraesuis, S. dublin et S. gallinarum induite chez la souris par S. abortusovis et S. gallinarum: charge bactérienne et réponse immunitaire humorale. La protection croisée induite par Abortusovis et Gallinarum a été étudiée après une épreuve vis-à-vis de ces deux sérotypes de Salmonelles ainsi que de Dublin et Choleraesuis, autres sérotypes de Salmonelles. Abortusovis induit une protection croisée significative contre les autres sérotypes de salmonelles. Gallinarum n'induit pas de protection effective contre Choleraesuis. En revanche même avec une multiplication faible chez la souris, Gallinarum J91 est capable d'induire une protection faible mais significative contre Dublin (même sérotype O). Les anticorps du sang ont été titrés par ELISA contre les antigènes de salmonelles spécifiques de la souche utilisée pour la sensibilisation ou l'épreuve. Gallinarum J91 a donné des réactions de reconnaissances antigéniques, bien supérieures à celles obtenues avec les autres sérotypes. Devant la variabilité de réponses des différentes souches vis-à-vis des différents antigènes, il est difficile de relier la présence d'anticorps IgM ou IgG à l'induction d'une protection. Toutefois, la liaison négative qui existe entre le taux de bactéries dans la rate de souris éprouvées par Gallinarum ou Dublin et le taux d'anticorps IgM et IgG dirigés contre la souche sensibilisante de Gallinarum, pourrait être expliquée par une réponse immunitaire contre le même sérotype du groupe O

Two In Vivo Models to Study Salmonella Asymptomatic Carrier State in Chicks

International audienceIn chicken, Salmonella Enteritidis and Salmonella Typhimurium, the two main serotypes isolated in human infections, can persist in the host organism for many weeks and up to many years without causing any symptoms. This persistence generally occurs after a short systemic infection that may either lead to death of very young birds or develop into cecal asymptomatic persistence, which is often accompanied by a high level of bacterial excretion, facilitating Salmonella transmission to counterparts. Here we describe two models of chick infection. The first model reproduces well the poultry infection in farm flocks. Numerous reinfections and animal-animal recontaminations occur leading to a high level of cecal colonization and fecal excretion in all chicks in the flock, over several weeks. In the second model, these animal reinfections and recontaminations are hampered leading to heterogeneity of infection characterized by the presence of low and super-shedders. This model allows for more mechanistic studies of Salmonella/chicks interactions as animal recontaminations are lowered

L’approche microbiote : stratégies pour prédire et prévenir les infections à Salmonella chez le poulet

National audienceSalmonellosis is one of the most important zoonosis worldwide resulting in a significant loss to agrifood industry as well as a substantial burden on the healthcare system. Depending of the hosts and the serotypes, Salmonella induce a wide spectrum of diseases among which typhoid fevers, asymptomatic infections and gastroenteritis. Poultry, which are the main source of human contamination, are mainly asymptomatic carriers. This asymptomatic Salmonella carrier state is thus a major issue for the European authority of food safety (EFSA) and the European center of prevention and control of the diseases (ECDC). Numerous strategies have been developed to fight Salmonella infections leading to a decrease or at least a stabilisation of the human cases. To go further, novel approaches must be developed in particular in response to the increase and spread of antimicrobial resistance. This article describes the current and future strategies used to fight Salmonella infection especially those related to the chicken gut microbiota. We finally address the new avenues opened by studies on host-microbiota-pathogen relationships.La salmonellose est l’une des zoonoses dont le fardeau économique et sanitaire est le plus élevé dans le monde. En fonction de l’hôte et du sérotype, Salmonella peut induire un large spectre de maladies qui vont des fièvres typhoïdes aux infections asymptomatiques en passant par les gastroentérites. Les volailles, qui sont majoritairement porteuses asymptomatiques, sont les principales sources de contamination de l’homme et l’un des enjeux majeurs pour l’autorité européenne de sécurité des aliments (EFSA) et le centre européen de prévention et de contrôle des maladies (ECDC). De nombreuses stratégies de lutte au niveau de l’élevage ont été mises en place pour combattre les infections à Salmonella, ce qui a permis de réduire ou au moins stabiliser le nombre d’infections humaines. Pour aller plus loin, de nouvelles stratégies doivent être mises en place, en particulier face à la diminution de l’utilisation des antibiotiques en élevage. Cet article décrit les différentes stratégies de lutte, actuelles et à venir, et en particulier celles liées aux travaux sur le microbiote intestinal du poulet. Il aborde également les conséquences que peuvent avoir les recherches sur les interactions microbiote-hôte-pathogèn

Faecal gut microbiota composition determines susceptibility to Salmonella Enteritidis primo-colonization

International audienceThe MoMIR-PPC project:The project aims to develop new approaches to predict, identify and prevent the appearance of animal and human super-shedders based on immune response and gut microbiota (GM) composition. The project focuses on four objectives. 1-Decipher why some animals become super-shedders or human become chronic carriers. 2-Identify immune and microbiota biomarkers to detect super-shedders and/ or prolonged carriers. 3-Define preventive and control measures by the characterisation of prebiotics, probiotics and nutraceutical products. 4-Develop mathematical models to provide new risk management tools and a pool of biosecurity measures at the farm levels. For this purpose, we have focused our research on Salmonella infections, which are an important economic and public health problem worldwide. Our INRA project:The development of a new infection model in isolator, where animal reinfections are greatly reduced, demonstrated that two main shedding phenotypes may emerge within a same chicken genetic background. Depending on the levels of Salmonella faecal excretion and caecal colonization levels, we may define the super- and low-shedder categories. In this project, we analysed the role of 1-gut microbiota, 2-immune status of chicks, 3-virulence of Salmonella strains.Metabarcoding characterization showed that GM composition before infection partly determined the levels of Salmonella colonization. Consistent with this idea, the transfer of GM, collected before infection from individuals that later developed the super-shedding syndrome yielded to the development of the super-shedder phenotype. In the same way, the transplantation of GM taken from adults, which are more resistant than chicks, can transfer resistance to Salmonella colonization. The analysis of GM composition before and after infection revealed significant differences among super and low-shedder chicks.In conclusion, some gut bacteria present before infection in low-shedder animals could be used as protective probiotics or as biomarkers. These results also suggest that Salmonella colonization is inhibited and/or promoted by a subset of microbes naturally found, before Salmonella colonization, in varying abundances within the GM

Etude de la présentation antigènique induite par voie conjonctivale chez le mouton

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Would <em>Salmonella</em> <em>Enteritidis</em> modify social behaviour in contamined chickens ?

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Les niveaux d’excrétion de <em>Salmonella</em> sont liés à la composition du microbiota intestinal chez le Poulet

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