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

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

A

Ant colony optimisation for planning safe escape routes

An emergency requiring evacuation is a chaotic event filled with uncertainties both for the people affected and rescuers. The evacuees are often left to themselves for navigation to the escape area. The chaotic situation increases when a predefined escape route is blocked by a hazard, and there is a need to re-think which escape route is safest. This paper addresses automatically finding the safest escape route in emergency situations in large buildings or ships with imperfect knowledge of the hazards. The proposed solution, based on Ant Colony Optimisation, suggests a near optimal escape plan for every affected person — considering both dynamic spread of hazards and congestion avoidance.The solution can be used both on an individual bases, such as from a personal smart phone of one of the evacuees, or from a remote location by emergency personnel trying to assist large groups

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

Comparison of bio-inspired algorithms applied to the coordination of mobile robots considering the energy consumption

Many applications, related to autonomous mobile robots, require to explore in an unknown environment searching for static targets, without any a priori information about the environment topology and target locations. Targets in such rescue missions can be fire, mines, human victims, or dangerous material that the robots have to handle. In these scenarios, some cooperation among the robots is required for accomplishing the mission. This paper focuses on the application of different bio-inspired metaheuristics for the coordination of a swarm of mobile robots that have to explore an unknown area in order to rescue and handle cooperatively some distributed targets. This problem is formulated by first defining an optimization model and then considering two sub-problems: exploration and recruiting. Firstly, the environment is incrementally explored by robots using a modified version of ant colony optimization. Then, when a robot detects a target, a recruiting mechanism is carried out to recruit a certain number of robots to deal with the found target together. For this latter purpose, we have proposed and compared three approaches based on three different bio-inspired algorithms (Firefly Algorithm, Particle Swarm Optimization, and Artificial Bee Algorithm). A computational study and extensive simulations have been carried out to assess the behavior of the proposed approaches and to analyze their performance in terms of total energy consumed by the robots to complete the mission. Simulation results indicate that the firefly-based strategy usually provides superior performance and can reduce the wastage of energy, especially in complex scenarios