title: Interactions of highly and low virulent Flavobacterium columnare isolates with gill tissue in carp and rainbow trout.
abstract: The interactions of Flavobacterium columnare isolates of different virulence with the gills of carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss Walbaum) were investigated. Both fish species were exposed to different high (HV) or low virulence (LV) isolates and sacrificed at seven predetermined times post-challenge. Histopathological and ultrastructural examination of carp and rainbow trout inoculated with the HV-isolate disclosed bacterial invasion and concomitant destruction of the gill tissue, gradually spreading from the filament tips towards the base, with outer membrane vesicles surrounding most bacterial cells. In carp, 5-10% of the fish inoculated with the LV-isolate became moribund and their gill tissue displayed the same features as described for the HV-isolate, albeit to a lesser degree. The bacterial numbers retrieved from the gill tissue were significantly higher for HV- compared to LV-isolate challenged carp and rainbow trout. TUNEL-stained and caspase-3-immunostained gill sections demonstrated significantly higher apoptotic cell counts in carp and rainbow trout challenged with the HV-isolate compared to control animals. Periodic acid-Schiff/alcian blue staining demonstrated a significantly higher total gill goblet cell count for HV- and LV-isolate challenged compared to control carp. Moreover, bacterial clusters were embedded in a neutral matrix while being encased by acid mucins, resembling biofilm formation. Eosinophilic granular cell counts were significantly higher in the HV-isolate compared to LV-isolate inoculated and control carp. The present data indicate a high colonization capacity, and the destructive and apoptotic-promoting features of the HV-isolate, and point towards important dynamic host mucin-F. columnare interactions warranting further research.
authors.affiliation: Department Morphology, Ghent University, Faculty of Veterinary Medicine, Salisburylaan 133, 9820, Merelbeke, Belgium. andclerc.declercq@ugent.be.
authors.forename: Annelies Maria
authors.initials: AM
authors.lastname: Declercq
authors.affiliation: Department of Pathology, Bacteriology and Poultry diseases, Ghent University, Faculty of Veterinary Medicine, Salisburylaan 133, 9820, Merelbeke, Belgium. koen.chiers@ugent.be.
authors.forename: Koen
authors.initials: K
authors.lastname: Chiers
authors.affiliation: Department Morphology, Ghent University, Faculty of Veterinary Medicine, Salisburylaan 133, 9820, Merelbeke, Belgium. wim.vandenbroeck@ugent.be.
authors.forename: Wim
authors.initials: W
authors.lastname: Van den Broeck
authors.affiliation: Department of Reproduction, Obstetrics and Herd Health, Ghent University, Faculty of Veterinary Medicine, Salisburylaan 133, 9820, Merelbeke, Belgium. jeroen.dewulf@ugent.be.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Dewulf
authors.affiliation: Department of Pathology, Bacteriology and Poultry diseases, Ghent University, Faculty of Veterinary Medicine, Salisburylaan 133, 9820, Merelbeke, Belgium. venessa.eeckhaut@ugent.be.
authors.forename: Venessa
authors.initials: V
authors.lastname: Eeckhaut
authors.affiliation: Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. maria.cornelissen@ugent.be.
authors.forename: Maria
authors.initials: M
authors.lastname: Cornelissen
authors.affiliation: Ghent University, Laboratory of Aquaculture and Artemia Reference Center, Rozier 44, 9000, Ghent, Belgium. peter.bossier@ugent.be.
authors.forename: Peter
authors.initials: P
authors.lastname: Bossier
authors.affiliation: Department of Pathology, Bacteriology and Poultry diseases, Ghent University, Faculty of Veterinary Medicine, Salisburylaan 133, 9820, Merelbeke, Belgium. freddy.haesebrouck@ugent.be.
authors.forename: Freddy
authors.initials: F
authors.lastname: Haesebrouck
authors.affiliation: Department Morphology, Ghent University, Faculty of Veterinary Medicine, Salisburylaan 133, 9820, Merelbeke, Belgium. annemie.decostere@ugent.be.
authors.forename: Annemie
authors.initials: A
authors.lastname: Decostere
mesh_terms: D000818:Animals; D002347:Carps; D053148:Caspase 3 / Q000737:chemistry; D005393:Fish Diseases / Q000382:microbiology*; D045826:Flavobacteriaceae Infections / Q000382:microbiology / Q000662:veterinary*; D005417:Flavobacterium / Q000472:pathogenicity* / Q000502:physiology; D005880:Gills / Q000473:pathology / Q000821:virology; D020287:In Situ Nick-End Labeling / Q000662:veterinary; D017686:Oncorhynchus mykiss; D014774:Virulence
chemical_list: D053148:Caspase 3