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Open Access Research

Stress induced Salmonella Typhimurium recrudescence in pigs coincides with cortisol induced increased intracellular proliferation in macrophages

Elin Verbrugghe1*, Filip Boyen1, Alexander Van Parys1, Kim Van Deun1, Siska Croubels2, Arthur Thompson3, Neil Shearer3, Bregje Leyman1, Freddy Haesebrouck1 and Frank Pasmans1

Author Affiliations

1 Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium

2 Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium

3 Department of Foodborne Bacterial Pathogens, Institute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4, UK

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Veterinary Research 2011, 42:118  doi:10.1186/1297-9716-42-118

Published: 7 December 2011

Abstract

Salmonella Typhimurium infections in pigs often result in the development of carriers that intermittently excrete Salmonella in very low numbers. During periods of stress, for example transport to the slaughterhouse, recrudescence of Salmonella may occur, but the mechanism of this stress related recrudescence is poorly understood. Therefore, the aim of the present study was to determine the role of the stress hormone cortisol in Salmonella recrudescence by pigs. We showed that a 24 h feed withdrawal increases the intestinal Salmonella Typhimurium load in pigs, which is correlated with increased serum cortisol levels. A second in vivo trial demonstrated that stress related recrudescence of Salmonella Typhimurium in pigs can be induced by intramuscular injection of dexamethasone. Furthermore, we found that cortisol, but not epinephrine, norepinephrine and dopamine, promotes intracellular proliferation of Salmonella Typhimurium in primary porcine alveolar macrophages, but not in intestinal epithelial cells and a transformed cell line of porcine alveolar macrophages. A microarray based transcriptomic analysis revealed that cortisol did not directly affect the growth or the gene expression or Salmonella Typhimurium in a rich medium, which implies that the enhanced intracellular proliferation of the bacterium is probably caused by an indirect effect through the cell. These results highlight the role of cortisol in the recrudescence of Salmonella Typhimurium by pigs and they provide new evidence for the role of microbial endocrinology in host-pathogen interactions.