Flexibacter maritimus associated with a bacterial stomatitis in Atlantic salmon smolts reared in net-pens in British Columbia

Filamentous yellow-pigmented bacteria (YPB) were consistently isolated from outbreaks of bacterial stomatitis ("mouth rot") affecting smelts of Atlant ic salmon Salmo salar after seawater entry in British Columbia. Six represe ntative YPB isolates were selected, and phenotypic characterization demonst rated that they shared morphological, physiological, and biochemical simila rities with the Flexibacter maritimus reference strains ATCC 43397 and ATCC 43398(T) (type strain). Polyclonal antisera raised against one British Col umbia mouth rot isolate (MRJ) and strains ATCC 43397 and ATCC 43398(T) were used to examine the antigenic relationships between the YPB from British C olumbia and these reference strains. Using agglutination, immunodiffusion, and western immunoblots, it was demonstrated that the British Columbian YPB were antigenically related to ATCC 43397 and ATCC 43398(T). Furthermore, i mmunohistochemistry indicated that the filamentous YPB recovered from outbr eaks of mouth rot were antigenically related to those seen histologically. Taken together, it was concluded that these YPB recovered from Atlantic sal mon mouth rot in British Columbia are strains of F. maritimus.