Survival of Salmonella serovar Typhimurium inside porcine monocytes is associated with complement binding and suppression of the production of reactive oxygen species

Macrophages are thought to play a major role in the development of Salmonella carriers in swine. It was the aim of the present study to characterize the interactions of a Salmonella serovar Typhimurium strain with porcine peripheral blood monocytes. The production of reactive oxygen species (ROS) by monocytes and the numbers of intracellularly killed bacteria differed significantly between the different pigs used. Opsonization of Salmonella bacteria with complement significantly decreased bacterial killing. Interestingly, monocytic ROS production was suppressed by metabolically active bacteria. In conclusion, binding to host complement and suppression of monocyte ROS production enable ser. Typhimurium to survive for at least 6 hours in porcine monocytes. Moreover, individual differences of porcine monocytes to produce ROS and to kill the intracellular Salmonella bacteria might account for the development of the carrier state in some pigs and not in others

From the gut to the peripheral tissues : the multiple effects of butyrate

Butyrate is a natural substance present in biological liquids and tissues. The present paper aims to give an update on the biological role of butyrate in mammals, when it is naturally produced by the gastrointestinal microbiota or orally ingested as a feed additive. Recent data concerning butyrate production delivery as well as absorption by the colonocytes are reported. Butyrate cannot be detected in the peripheral blood, which indicates fast metabolism in the gut wall and/or in the liver. In physiological conditions, the increase in performance in animals could be explained by the increased nutrient digestibility, the stimulation of the digestive enzyme secretions, a modification of intestinal luminal microbiota and an improvement of the epithelial integrity and defence systems. In the digestive tract, butyrate can act directly (upper gastrointestinal tract or hindgut) or indirectly (small intestine) on tissue development and repair. Direct trophic effects have been demonstrated mainly by cell proliferation studies, indicating a faster renewal of necrotic areas. Indirect actions of butyrate are believed to involve the hormono-neuro-immuno system. Butyrate has also been implicated in down-regulation of bacteria virulence, both by direct effects on virulence gene expression and by acting on cell proliferation of the host cells. In animal production, butyrate is a helpful feed additive, especially when ingested soon after birth, as it enhances performance and controls gut health disorders caused by bacterial pathogens. Such effects could be considered for new applications in human nutrition

The influence of fatty acids on the expression of virulence genes of Salmonella Typhimurium and the colonization of pigs

Salmonella Typhimurium infections in pigs are a major source of human foodborne salmonellosis. To reduce the number of infected pigs, actdified feed or drinking water can be administrated. A study was carried out to evaluate the use of short-chain fatty acids (SCFA) and medium-chain fatty acids (MCFA) for the control of Salmonella Typhimurium infections in ptgs. Short-chain fatty acids formate, acetate, propionate and butyrate (pH 6, osm 600, cone 1 OmM) and medium-chain fatty acids caproic, caprylic and capric acid (pH6, osm 600, cone 2mM) were used

SPI-2 of Salmonella Typhimurium is not necessary for long term colonization of pigs

Unravelling the role of Salmonella virulence factors in the porcine host could greatly contribute to the development of control measures such as vaccination. The virulence genes located on the Salmonella Pathogenicity Island 2 (SPI-2) are indispensable for the induction of systemic disease and persistence in BALB/c mice. The role of this pathogenicity island in the pathogenesis of Salmonella Typhimurium infections in pigs is not documented. Therefore, in the present study, the interactions of a porcine field strain of Salmonella Typhimurium and a non-polar isogenic SPI-2 (D-ssrA) deletion mutant were compared in both in vitro and in vivo models. The ssrA mutant strain displayed decreased SPI-2 expression levels in vitro and was attenuated in a mouse model after oral inoculation. No difference was seen in the expression of SPI-1 related virulence genes. Through flowcytometric analysis, the ssrA mutant strain was found to be moderately attenuated in intracellular replication in porcine macrophages in vitro. In an infection experiment, 2 groups of 10 piglets were orally inoculated with the wild type or the ssrA mutant strain. The infection of the animals inoculated with the ssrA mutant strain followed a similar course as the animals infected with the wild type strain. At days 5 and 28 post inoculation, the animals of both groups were infected to the same extent in the gut and gut-associated lymphoid tissue, as well as in the mternal organs. These results suggest that SPI-2 of Salmonella Typhimurium may not contribute to the colonization of pigs to the same extent as it contributes to the colonization of BALB/c mice

Characterization of the adhesion of <i>Flavobacterium columnare</i> (<i>Flexibacter columnaris</i> to gill tissue

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Antimicrobial resistance of Escherichia coli and Enterococcus faecalis in housed laying-hen flocks in Europe

The aim of this study was to determine the potential association between housing type and multiple drug resistance (MDR) in Escherichia coli and Enterococcus faecalis isolates recovered from 283 laying-hen flocks. In each flock, a cloacal swab from four hens was collected and produced 1102 E. coli and 792 E. faecalis isolates. Broth microdilution was used to test susceptibility to antimicrobials. Country and housing type interacted differently with the MDR levels of both species. In the E. coli model, housing in a raised-floor system was associated with an increased risk of MDR compared to the conventional battery system [odds ratio (OR) 2·12, 95% confidence interval (CI) 1·13-3·97)]. In the E. faecalis model the MDR levels were lower in free-range systems than in conventional battery cages (OR 0·51, 95% CI 0·27-0·94). In Belgium, ceftiofur-resistant E. coli isolates were more numerous than in the other countrie