General Information: Aeromonas salmonicida subsp. salmonicida A449 was isolated from a brown trout with furunculosis. The agent of furunculosis, a major cause of mortality among salmonid fishes. This bacterium is the causal agent of furunculosis. Although it was discovered nearly 100 years ago, it is not known how the diesase is spread. Furunculosis is temperature sensistive, with acute cases occurring when the water is above 20 degrees C and chronic cases developing at temperatures below 13 degrees C. The acute form of the disease causes the fish to turn a dark color and stop eating.