Damaging effect of the fish pathogen Aeromonas salmonicida ssp. salmonicida on intestinal enterocytes of Atlantic salmon (Salmo salar L.).
In fish, bacterial pathogens can enter the host by one or more of three different routes: (a) skin, (b) gills and (c) gastrointestinal tract. Bacteria can cross the gastrointestinal lining in three different ways. In undamaged tissue, bacteria can translocate by transcellular or paracellular routes. Alternatively, bacteria can damage the intestinal lining with extracellular enzymes or toxins before entering. Using an in vitro (Ussing chamber) model, this paper describes intestinal cell damage in Atlantic salmon (Salmo salar L.) caused by the fish pathogen Aeromonas salmonicida ssp. salmonicida, the causative agent of furunculosis. The in vitro method clearly demonstrated substantial detachment of enterocytes from anterior region of the intestine (foregut) upon exposure to the pathogen. In the hindgut (posterior part of the intestine), little detachment was observed but cellular damage involved microvilli, desmosomes and tight junctions. Based on these findings, we suggest that A. salmonicida may obtain entry to the fish by seriously damaging the intestinal lining. Translocation of bacteria through the foregut (rather than the hindgut) is a more likely infection route for A. salmonicida infections in Atlantic salmon.
Ringø
Einar
E
Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, 9292 Tromsø, Norway. einar.ringo@veths.no
Jutfelt
Fredrik
F
Kanapathippillai
Premasany
P
Bakken
Yvonne
Y
Sundell
Kristina
K
Glette
Johan
J
Mayhew
Terry M
TM
Myklebust
Reidar
R
Olsen
Rolf Erik
RE
D048409:Aeromonas salmonicida / Q000472:pathogenicity / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D004195:Disease Models, Animal; D020895:Enterocytes / Q000382:microbiology / Q000648:ultrastructure*; D005667:Furunculosis / Q000382:microbiology / Q000473:pathology*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000473:pathology*; D046529:Microscopy, Electron, Transmission; D009924:Organ Culture Techniques; D020317:Salmo salar