Developing an experimental necrotic enteritis model in turkeys - the impact of Clostridium perfringens, Eimeria meleagrimitis and host age on frequency of severe intestinal lesions.

Background: Necrotic enteritis is a significant problem to the poultry industry globally and, in Norway up to 30% of Norwegian turkey grow-outs can be affected. However, despite an awareness that differences exist between necrotic enteritis in chickens and turkeys, little information exists concerning the pathogenesis, immunity, microbiota or experimental reproduction of necrotic enteritis in turkeys. In particular, it is important to determine the appearance of the gross lesions, the age dependency of the disease and the role of netB toxin of Clostridium perfringens.

Analysis of Campylobacter jejuni infection in the gnotobiotic piglet and genome-wide identification of bacterial factors required for infection.

To investigate how Campylobacter jejuni causes the clinical symptoms of diarrhoeal disease in humans, use of a relevant animal model is essential. Such a model should mimic the human disease closely in terms of host physiology, incubation period before onset of disease, clinical signs and a comparable outcome of disease. In this study, we used a gnotobiotic piglet model to study determinants of pathogenicity of C.

Multivariate evaluation of the effectiveness of treatment efficacy of cypermethrin against sea lice (Lepeophtheirus salmonis) in Atlantic salmon (Salmo salar).

Background: The sea louse Lepeophtheirus salmonis is the most important ectoparasite of farmed Atlantic salmon (Salmo salar) in Norwegian aquaculture. Control of sea lice is primarily dependent on the use of delousing chemotherapeutants, which are both expensive, and toxic to other wildlife. The method most commonly used for monitoring treatment effectiveness relies on measuring the percentage reduction in the mobile stages of Lepeophtheirus salmonis only.

Type C and C/D toxigenic Clostridium botulinum is not normally present in the intestine of healthy broilers.

Toxigenic Clostridium botulinum spores are widely distributed in wetland environments and are frequently recovered from healthy wild birds, where ingestion of toxic maggots from carcasses is considered a major initiating factor for botulism outbreaks. Toxic carcasses can perpetuate an existing outbreak also in poultry, but their importance as an initiating factor for poultry botulism is less clear. Although toxigenic C.

Structural and functional analysis of the pore-forming toxin NetB from Clostridium perfringens.

Clostridium perfringens is an anaerobic bacterium that causes numerous important human and animal diseases, primarily as a result of its ability to produce many different protein toxins. In chickens, C. perfringens causes necrotic enteritis, a disease of economic importance to the worldwide poultry industry.

Inhibition of cytotoxicity by the Nhe cytotoxin of Bacillus cereus through the interaction of dodecyl maltoside with the NheB component.

Nhe ('nonhaemolytic enterotoxin') is a three-component cytotoxin implicated in the pathogenesis of diarrhoea by Bacillus cereus. Nhe forms pores in pure lipid bilayers, but the function of the individual components (NheA, NheB and NheC) remains unclear. NheB and NheC are structural homologues of ClyA, a pore-forming cytotoxin of Escherichia coli.

Relative entropy differences in bacterial chromosomes, plasmids, phages and genomic islands.

Background: We sought to assess whether the concept of relative entropy (information capacity), could aid our understanding of the process of horizontal gene transfer in microbes. We analyzed the differences in information capacity between prokaryotic chromosomes, genomic islands (GI), phages, and plasmids. Relative entropy was estimated using the Kullback-Leibler measure.

The use of a porcine intestinal cell model system for evaluating the food safety risk of Bacillus cereus probiotics and the implications for assessing enterotoxigenicity.

The use of porcine intestinal cell lines in assessing toxicity of Bacillus cereus probiotics in conjunction with animal challenge trials with toxigenic B. cereus was investigated. Toxigenic and toxin deletion mutants of B.

Formation of very large conductance channels by Bacillus cereus Nhe in Vero and GH(4) cells identifies NheA + B as the inherent pore-forming structure.

The nonhemolytic enterotoxin (Nhe) produced by Bacillus cereus is a pore-forming toxin consisting of three components, NheA, -B and -C. We have studied effects of Nhe on primate epithelial cells (Vero) and rodent pituitary cells (GH(4)) by measuring release of lactate dehydrogenase (LDH), K(+) efflux and the cytosolic Ca(2+) concentration ([Ca(2+)](i)). Plasma membrane channel events were monitored by patch-clamp recordings.

Analysis of intra-genomic GC content homogeneity within prokaryotes.

Background: Bacterial genomes possess varying GC content (total guanines (Gs) and cytosines (Cs) per total of the four bases within the genome) but within a given genome, GC content can vary locally along the chromosome, with some regions significantly more or less GC rich than on average. We have examined how the GC content varies within microbial genomes to assess whether this property can be associated with certain biological functions related to the organism's environment and phylogeny. We utilize a new quantity GCVAR, the intra-genomic GC content variability with respect to the average GC content of the total genome.

Cytotoxicity of the Bacillus cereus Nhe enterotoxin requires specific binding order of its three exoprotein components.

This study focuses on the interaction of the three components of the Bacillus cereus Nhe enterotoxin with particular emphasis on the functional roles of NheB and NheC. The results demonstrated that both NheB and NheC were able to bind to Vero cells directly while NheA lacked this ability. It was also shown that Nhe-induced cytotoxicity required a specific binding order of the individual components whereby the presence of NheC in the priming step as well as the presence of NheA in the final incubation step was mandatory.

Stretches of alternating pyrimidine/purines and purines are respectively linked with pathogenicity and growth temperature in prokaryotes.

Background: The genomic fractions of purine (RR) and alternating pyrimidine/purine (YR) stretches of 10 base pairs or more, have been linked to genomic AT content, the formation of different DNA helices, strand-biased gene distribution, DNA structure, and more. Although some of these factors are a consequence of the chemical properties of purines and pyrimidines, a thorough statistical examination of the distributions of YR/RR stretches in sequenced prokaryotic chromosomes has to the best of our knowledge, not been undertaken. The aim of this study is to expand upon previous research by using regression analysis to investigate how AT content, habitat, growth temperature, pathogenicity, phyla, oxygen requirement and halotolerance correlated with the distribution of RR and YR stretches in prokaryotes.

Demonstration of a cholesterol-dependent cytolysin in a noninsecticidal Bacillus sphaericus strain and evidence for widespread distribution of the toxin within the species.

During the course of screening Bacillus species from food and water in Norway, we isolated a strain of Bacillus sphaericus of DNA homology group V, not previously recognized to contain entomopathogenic strains, that was cytotoxic to Vero cell epithelia. Peptide mass fingerprinting of a protein purified from the culture supernatant of B. sphaericus B354 identified a cholesterol-dependent cytolysin (CDC) with high amino acid sequence identity with sphaericolysin, a CDC identified recently in B.

Bacillus cereus Nhe is a pore-forming toxin with structural and functional properties similar to the ClyA (HlyE, SheA) family of haemolysins, able to induce osmotic lysis in epithelia.

The mechanism by which Bacillus cereus causes diarrhoea is unknown. Three putative enterotoxins have been proposed, haemolysin BL (Hbl), cytotoxin K and non-haemolytic enterotoxin (Nhe). Both Hbl and Nhe are three-component cytotoxins and maximal cytotoxicity of Nhe against epithelia is dependent on all three components.

Campylobacter jejuni inhibits the absorptive transport functions of Caco-2 cells and disrupts cellular tight junctions.

Caco-2 cells are models of absorptive enterocytes. The net transport of fluid from apical to basolateral surfaces results in 'domes' forming in differentiated monolayers. Here, the effect of Campylobacter jejuni on this process has been examined.

Single channel evidence for innate pore-formation by Vibrio parahaemolyticus thermostable direct haemolysin (TDH) in phospholipid bilayers.

Vibrio parahaemolyticus thermostable direct haemolysin (TDH) is widely considered to be a pore-forming toxin. The protein has no significant homology to other known pore-forming toxins and its mechanism of action in vivo remains undefined. We demonstrate single channel pore-forming activity of V.

Genetic and functional analysis of the cytK family of genes in Bacillus cereus.

CytK is a pore-forming toxin of Bacillus cereus that has been linked to a case of necrotic enteritis. PCR products of the expected size were generated with cytK primers in 13 of 29 strains. Six strains were PCR-positive for the related gene hly-II, which encodes haemolysin II, a protein that is 37 % identical to the original CytK.

Activation of Maxi Cl(-) channels by antiestrogens and phenothiazines in NIH3T3 fibroblasts.

The identification of alternative estrogen actions has been accumulating steadily over the past two decades. Typically, these novel actions are not directly related to nuclear transcriptional events but related to the interaction of estrogens with sites present at plasma membrane or cytosolic locations. These alternative effects, widely known as non-genomic effects, range from the modulation of plasma membrane ion channel activity to the regulation of different intracellular signalling cascades.