New perspectives from genomic analyses of bacterial infectious agents.

Recent advances in the technologies for genomic sequencing and systems for handling and processing sequencing data have transformed bacterial genomics into a near-routine approach for both small- and large-scale investigations of infectious agents. Nonetheless, the application of genomics - especially largerscale studies - to animal infectious agents lags behind its application to human pathogens, despite the growing importance of many animal species as food sources. Assiduously conducted genomic studies offer major benefits, not merely by providing a detailed understanding of infectious agents but also through the exploitation of such findings to enable more accurate diagnosis, high-resolution typing and the development of improved interventions. The use of genomics for these and other purposes is likely to grow in future years and it must be anticipated that investigation and characterisation of important animal infectious agents will also gain considerable benefits. Using mainly animal pathogens as examples - including several infectious agents listed by the World Organisation for Animal Health - this paper provides a concise summary of some recent purposes and developments in bacterial genomics analysis.

Les récentes avancées technologiques réalisées dans le domaine du séquençage du génome et la mise au point de systèmes permettant de manipuler et de traiter les données de séquençage ont transformé la génomique bactérienne en une méthode utilisée quasiment au quotidien dans le cadre d'études à grande ou à petite échelle sur les agents infectieux. Néanmoins, s'agissant d'agents pathogènes affectant les animaux, les applications de la génomique sont bien moins avancées que dans le domaine des agents pathogènes humains, en particulier dans le cadre d'études à grande échelle et ce, malgré l'utilisation croissante de nombreuses espèces animales dans l'alimentation. Les études génomiques réalisées en continu offrent des avantages considérables, non seulement parce qu'elles apportent des informations précises pour mieux comprendre les agents de maladies infectieuses mais aussi par leurs applications concrètes, qui permettent d'obtenir une meilleure justesse de diagnostic, de procéder à un typage de haute résolution et de concevoir des interventions plus efficaces. De telles applications et d'autres encore à venir vont probablement se développer considérablement dans un futur proche et nous pouvons nous attendre à ce qu'elles soient enfin utilisées pour étudier et caractériser les principaux agents pathogènes affectant les animaux. Les auteurs résument les objectifs de l'analyse des génomes bactériens et ses accomplissements les plus récents, en illustrant leur propos d'exemples portant essentiellement sur des pathogènes affectant les animaux, dont plusieurs figurent sur la liste de l'Organisation mondiale de la santé animale.

Gracias a los últimos adelantos de las técnicas de secuenciación genómica y de los sistemas para procesar y explotar los datos resultantes, la genómica bacteriana se utiliza ahora de modo casi sistemático en el estudio (a pequeña o a gran escala) de agentes infecciosos. Sin embargo, pese a la creciente importancia que están cobrando muchas especies animales como fuente de productos alimentarios, la aplicación de la genómica a los agentes infecciosos animales (especialmente en los estudios a gran escala) aún va rezagada con respecto a su aplicación a los patógenos humanos. La realización asidua de estudios genómicos depara grandes beneficios, no solo porque procura un detallado conocimiento de los agentes infecciosos, sino también porque este saber sirve después para efectuar diagnósticos más exactos, hacer tipificaciones de alta resolución y definir intervenciones terapéuticas más eficaces. Es muy probable que el uso de la genómica con estos y otros fines vaya en aumento en los próximos años, y cabe augurar que también se extenderá al estudio y la caracterización de importantes agentes infecciosos animales. Tomando básicamente como ejemplo una serie de patógenos animales (entre ellos varios agentes infecciosos incluidos en la lista de la Organización Mundial de Sanidad Animal), los autores resumen con concisión los objetivos y avances de una serie de recientes trabajos de análisis del genoma bacteriano.

Risk factors associated with Lawsonia intracellularis in English pig farms.

Porcine proliferative enteropathy (PPE) caused by the bacterium Lawsonia intracellularis causes considerable economic loss to the pig industry. The objective of this study was to evaluate the seroprevalence of L. intracellularis exposure in different age groups of pigs (growers to finishers) within English farms and to identify potential risk factors. Samples were obtained in a cross-sectional study of 147 farms between 2008 and 2009. Twelve samples (six growers and six finishers) from each farm were tested for L. intracellularis by antibody ELISA. At animal level there was a significant positive linear trend between seroprevalence and age in weeks (r(2)=2.65, P<0.001), with seroprevalence lowest (24.73%) at 11 weeks and highest (93.33%) at 24 weeks. At farm level, seroprevalence was significantly lower in growers than finishers (56.80% vs. 94.26%, P<0.001). Farms reporting minor Salmonella problems and those that brought boars onto the farm had higher odds of testing positive in growers (OR 5.69 and 4.31, respectively. On the other hand, farms where producers considered temperature as an important stress factor (OR=0.3) and which had more than two sites on which pigs are kept (OR=0.16) were less likely to test positive in growers. The current study confirmed the high prevalence of L. intracellularis in English pig farms. The potential risk factors and further information of the disease impact on the farm productivity will aid the development of appropriate control strategies through better understanding of the disease.

Comparative molecular analysis of ovine and bovine Streptococcus uberis isolates.

Streptococcus uberis causes clinical and subclinical mastitis in cattle and sheep, but it is unknown whether the composition of Strep. uberis populations differs between host species. To address this, we characterized a collection of bovine and ovine Strep. uberis isolates with shared geographical and temporal origins by means of an expanded multilocus sequence typing scheme. Among 14 ovine and 35 bovine isolates, 35 allelic profiles were detected. Each allelic profile was associated with a single host species and all but one were new to the multilocus sequence typing database. The median number of new alleles per isolate was higher for ovine isolates than for bovine isolates. None of the ovine isolates belonged to the global clonal complexes 5 or 143, which are commonly associated with bovine mastitis and which have a wide geographical distribution. Ovine isolates also differed from bovine isolates in carriage of plasminogen activator genes, with significantly higher prevalence of pauB in ovine isolates. Isolates that were negative for yqiL, one of the targets of multilocus sequence typing, were found among ovine and bovine isolates and were not associated with a specific sequence type or global clonal complex. One bovine isolate carried a gapC allele that was probably acquired through lateral gene transfer, most likely from Streptococcus salivarius. We conclude that ovine isolates are distinct from bovine isolates of Strep. uberis, and that recombination between isolates from different host species or bacterial species could contribute to changes in virulence gene profiles with relevance for vaccine development.

Verotoxin-2 activates mitogen-activated protein kinases in bovine adherent peripheral blood mononuclear cells.

The effects of verotoxin (VT) on the mitogen-activated protein (MAP) kinase signalling pathways were investigated in bovine adherent peripheral blood mononuclear cells (PBMCs). VT2 stimulated a transient activation of both p38 MAP kinase and extracellular-regulated kinase (ERK) and stimulated an increase in tumour necrosis factor-α release from PBMCs. Bovine PBMCs react with very similar kinetics to human peripheral blood monocytes, despite the gross differences in disease outcome of the two species on infection with verotoxigenic Escherichia coli.

Host-response patterns of intramammary infections in dairy cows.

Many different bacterial species have the ability to cause an infection of the bovine mammary gland and the host response to these infections is what we recognize as mastitis. In this review we evaluate the pathogen specific response to the three main bacterial species causing bovine mastitis: Escherichia coli, Streptococcus uberis and Staphylococcus aureus. In this paper we will review the bacterial growth patterns, host immune response and clinical response that results from the intramammary infections. Clear differences in bacterial growth pattern are shown between bacterial species. The dominant pattern in E. coli infections is a short duration high bacteria count infection, in S. aureus this is more commonly a persistent infection with relative low bacteria counts and in S. uberis a long duration high bacteria count infection is often observed. The host immune response differs significantly depending on the invading bacterial species. The underlying reasons for the differences and the resulting host response are described. Finally we discuss the clinical response pattern for each of the three bacterial species. The largest contrast is between E. coli and S. aureus where a larger proportion of E. coli infections cause potentially severe clinical symptoms, whereas the majority of S. aureus infections go clinically unnoticed. The relevance of fully understanding the bovine host response to intramammary infection is discussed, some major gaps in our knowledge are highlighted and directions for future research are indicated.

Phenotypic and functional characterisation of follicle-associated epithelium of rectal lymphoid tissue.

Lymphoid follicles cluster in the terminal rectum of various animal species and of man and hence this site may be important in the development of immune responses to pathogens. For the induction of immune responses at mucosal sites, interplay is required between various cell types performing functions ranging from antigen-sampling cells via antigen-presenting cells to antigen-specific lymphocytes. Therefore, we have characterised the cell populations and relevant functioning of follicle-associated epithelium (FAE) and associated follicles in the terminal portion of rectum in cattle as a representative mammal. Immunohistochemical studies of this region identified immune cell subsets (CD4+, CD8+, WC 1+gammadelta, CD2+, CD 21+ and CD 40+ cells) characteristic of an immune-inductive site. Examination of FAE identified a subset of cells with structural and functional features of antigen-sampling M-cells. Cells of the FAE and adjacent follicle-associated crypts expressed vimentin and a subset of these cells internalised microparticles, a further attribute of M-cells. The FAE cells were phenotypically heterogeneous and therefore the function and phenotype of these cell subsets requires further characterisation, particularly with respect to their potentially important role in the interaction of hosts with pathogens and the development of immune responses.

Immunopathogenesis of experimentally induced proliferative enteropathy in pigs.

To characterize the immune response associated with Lawsonia intracellularis infection, twenty-eight, 7-week-old pigs were dosed orally with a pure culture of L. intracellularis. Animals were killed 3, 7, 14, 21, 28, 35, and 42 days postinfection. Light microscopic studies were undertaken to immunophenotype the immunologic response using specific antibodies to T-cell subsets (CD3, CD4, and CD8), B cells, major histocompatibility complex class II, cadherin, and macrophages over the course of time. The results indicate that there is a direct association between the presence of L. intracellularis and reduced T-cell and B-cell numbers. For the first time, this provides evidence of the presence of an immunosuppressive mechanism operating in this disease. Furthermore, macrophage marker studies indicated that macrophages may play a more complex and significant role in the disease process than has been previously reported, with activated macrophages accumulating in infected hyperplastic crypts.