Characteristics of <i>Lawsonia intracellularis</i> pathogenesis: recent research and potential benefits

Lawsonia intracellularis is defined clearly as the causative agent of proliferative enteropathies (PE). Disease continues to present significant problems worldwide. This bacterium has developed what appears to be a unique relationship with animal hosts and studies have focussed on molecular characterisation of L. intracellularis and examination of the host-pathogen relationship at cellular and molecular levels. The following is a brief review of work which has been conducted over the past 3 years together with an appraisal of possible benefits to the pig industry

Microbial biofilms: Does breaking the microbes’ community spirit hold the key to beating persistent mastitis?

No abstract availabl

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

Food fears Consumer attitudes to food in Wales

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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

Diagnosis and control of contagious caprine pleuropneumonia

Le diagnostic de la pleuropneumonie contagieuse caprine a souvent été jugé difficile, cette maladie pouvant être confondue avec d'autres mycoplasmoses des petits ruminants. Les symptômes et lésions peuvent être similaires et l'isolement de Mycoplasma capricolum subsp. capripneumoniae (MccF38) nécessite une bonne compétence technique. Une fois les souches MccF38 isolées, leur identification ne devrait pas poser de problème. De nouvelles techniques, telles que l'amplification en chaîne par polymerase, offrent désormais la possibilité d'identifier MccF38 directement à partir de prélèvements lyophilisés. Toutefois, l'isolement de souches MccF38 reste obligatoire pour une déclaration officielle d'infection. Jusqu'à présent, le test sérologique de référence était l'épreuve de fixation du complément, ses principaux inconvénients étant l'absence de sensibilité et de spécificité, ainsi que la brève persistance des anticorps décelés au moyen de cette technique. L'épreuve immuno-enzymatique (enzyme-linked immunosorbent assay : ELISA) de compétition, récemment mise au point, devrait désormais permettre de déterminer, à l'occasion de larges enquêtes sérologiques, la prévalence réelle de la maladie. Les traitements antibiotiques sont efficaces, mais ils ne peuvent prévenir la persistance d'un portage latent du mycoplasme. Unvaccin à mycoplasmes tués, adjuvé à la saponine, a été mis au poins au Kenya : il confère aux caprins une immunité d'environ un an. (Résumé d'auteur

Immunomagnetic separation of the intestinal spirochaetes Brachyspira pilosicoli and Brachyspira hyodysenteriae from porcine faeces

Porcine intestinal spirochaetes are fastidious anaerobic organisms and, as a consequence, it has been necessary to develop various protocols to enhance their isolation from or detection in faeces. Immunomagnetic separation (IMS) is a method developed recently to improve separation of target cells from mixed cell suspensions. The purpose of the present study was to compare the relative sensitivity of IMS for isolation of Brachyspira pilosicoli and Brachyspira hyodysenteriae with current routine diagnostic methods (culture on selective media and PCR) for detection of these microorganisms in pig faeces. Neither direct nor indirect IMS methods enhanced the sensitivity of detection of either organism when performed with the recommended washings during sample processing. Performance of the IMS procedure without washing gave sensitivity at levels similar to direct culture onto selective medium. Further development of IMS techniques is required to improve isolation rates of Brachyspira species from faecal samples

Expression by Lawsonia intracellularis of type III secretion system components during infection

Contact-dependent secretion systems, such as the type 111 secretion system (T3SS), have been shown to play significant roles in the pathogenicity of many Gram-negative bacterial pathogens. Lawsonia intracellularis is a novel, obligate intracellular Gram-negative bacterium, which has been identified as the etiological agent of proliferative enteropathies in numerous animal species. Analysis of the genome sequence of the L intracellularis strain PHE/MN1-00 has revealed the presence of a T3SS secretion system in this bacterium. In this study we aimed to determine whether this important virulence mechanism is also present in L intracellularis strain LR189/5/83. Using a PCR-based approach, we verified the presence of a genomic region encoding a T3SS. Specifically, a gene highly homologous to the yscN energiser component of the prototypic T3SS of Yersinia spp. was identified and termed lscN. Two further open reading frames (ORFs) contiguous with lscN were also identified: lscO and lscQ, which are also homologues of ORFs within the T3SS of Yersinia spp. To establish whether this T3SS may be functional, expression was monitored directly by RT-PCR and indirectly by detection of serological responses in vaccinated and infected animals. Transcripts for lscN and lscQ were detected and purified rLscQ was recognized by antiserum from infected pigs, indicating expression in vivo during infection. By analogy to other bacteria, this T3SS may be crucial for intracellular development and is likely to play a significant role in the virulence of this unusual pathogen

Immunization of cattle with a combination of purified intimin-531, EspA and Tir significantly reduces shedding of Escherichia coli O157:H7 following oral challenge

Enterohemorrhagic Escherichia call (EHEC) O157:H7 is a human pathogen that can cause gastrointestinal disease with potentially fatal consequences as a result of systemic Shiga toxin activity. Cattle are the main reservoir host of EHEC O157 and interventions need to be developed that prevent cattle colonization or limit shedding of the organism from this host. EHEC 0157 predominately colonizes the bovine terminal rectum and requires a type III secretion system (T3SS) for adherence and persistence at this site. A vaccine based on concentrated bacterial supernatant that contains T3S proteins has shown some efficacy. Here we have demonstrated that vaccination with a combination of antigens associated with T3S-mediated adherence; the translocon filament protein, EspA, the extracellular region of the outer membrane adhesin, intimin, and the translocated intimin receptor (Tir) significantly reduced shedding of EHEC 0157 from experimentally infected animals. Furthermore, this protection may be augmented by addition of H7 flagellin to the vaccine preparation that has been previously demonstrated to be partially protective in cattle. Protection correlates with systemic and mucosal antibody responses to the defined antigens and validates the targeting of these colonization factors