Characteristics of Filamentous Bacteria Isolated from a Gill Disease of Salmonids

Abstract

The morphological, physiological, and serological characteristics of 15 cultures of filamentous bacteria isolated in Japan (five isolates) and Oregon from cultured salmonids suffering from bacterial gill disease were determined and compared. The strains from each area were uniform in characteristics and apart from minor differences in temperature and salinity tolerances, each geographic group of isolates was physiologically similar. Serologically, however, although all strains possessed a common antigen, the Japanese and Oregon strains were distinct. It was found that all strains could readily colonize the gill epithelium of juvenile rainbow trout causing an asymptomatic infection, but in some experiments fatal gill disease was irregularly produced.Key words: bacterial gill disease, filamentous bacteria, salmonids