title: Cortisol directly impacts Flavobacterium columnare in vitro growth characteristics.
abstract: Teleost fish faced with stressful stimuli launch an endocrine stress response through activation of the hypothalamic-pituitary-interrenal axis to release glucocorticoids, in particular cortisol, into the blood. For the majority of bacterial fish pathogens, stress is considered a key factor in disease outbreaks. Based upon studies in mammals, there is considerable evidence to suggest that, besides impairing the immune system, cortisol can have a direct effect on bacterial cells. Hitherto, this intriguing field of microbial endocrinology has remained largely unexplored in aquatic diseases. The present study investigated in vitro the impact of cortisol on phenotypic traits of the fresh water fish pathogen Flavobacterium columnare. Colonies obtained from the highly virulent (HV) isolates resulted in significantly larger and more spreading colonies compared to those from the low virulent (LV) isolates. High cortisol doses added displayed a direct effect on the bacterial cells and induced a significant decrease in colony size. An additional intriguing finding was the inverse relationship between cortisol concentrations added to the broth and the spreading character of colonies retrieved, with higher cortisol doses resulting in less rhizoid to rough and even smooth colony formation (the latter only in the LV trout isolate), suggesting a dose-response effect. The loss of the rhizoid appearance of the F. columnare colonies upon administration of cortisol, and hence the loss of motility, might indicate a phenotypic change to the biofilm state. These findings form the basis for further research on the impact of glucocorticoids on other virulence factors and biofilm formation of F. columnare.
authors.affiliation: Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium. andclerc.declercq@ugent.be.
authors.forename: Annelies Maria
authors.initials: AM
authors.lastname: Declercq
authors.affiliation: Stress Physiology Research Group, Laboratory of Food Analysis, Department of Bio-analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.|Stress Physiology Research Group, Animal Sciences Unit, Institute for Agriculture and Fisheries Research, Melle, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Aerts
authors.affiliation: Biostatistics and Data modeling, Animal Sciences Unit, Institute for Agriculture and Fisheries Research, Melle, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Ampe
authors.affiliation: Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
authors.forename: Freddy
authors.initials: F
authors.lastname: Haesebrouck
authors.affiliation: Laboratory of Food Analysis, Department of Bio-analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: De Saeger
authors.affiliation: Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
authors.forename: Annemie
authors.initials: A
authors.lastname: Decostere
mesh_terms: D000818:Animals; D058491:Bacterial Load / Q000379:methods / Q000662:veterinary; D003470:Culture Media; D005393:Fish Diseases / Q000382:microbiology; D045826:Flavobacteriaceae Infections / Q000382:microbiology / Q000662:veterinary; D005417:Flavobacterium / Q000187:drug effects* / Q000254:growth & development; D008401:Gas Chromatography-Mass Spectrometry / Q000662:veterinary; D006854:Hydrocortisone / Q000032:analysis / Q000494:pharmacology*; D066298:In Vitro Techniques
chemical_list: D003470:Culture Media; D006854:Hydrocortisone