Survival of the fish pathogen Aeromonas salmonicida in the marine environment

Abstract. The fate of the fish pathogen Aeromonas salmonicida in the marine environment was examined by culture, epifluorcscence microscopy, the indirect fluorescent antibody technique (1FAT), direct viable counts (= Kogure technique) and the assessment of respiratory activity by the reduction of tetrazolium compounds to coloured formazans. In laboratory- based systems containing sediment, water, algae and invertebrates, cells of A. salmonicida were observed microscopically after plate counts on tryptone soya agar declined to zero. Survival was maximal at a salinity of 25%_o, and in wood and sediment, notably mud, rather than the water column.