A PROTEOLYTIC PSEUDOMONAD FROM SKIN LESIONS OF RAINBOW TROUT (SALMO GAIRDNERII): I. CHARACTERISTICS OF THE PATHOGENIC EFFECTS AND THE EXTRACELLULAR PROTEINASE

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Abstract
A fluorescent pseudomonad producing a powerful extracellular proteinase and closely resembling but not identical with Pseudomonas fluorescens was isolated from skin lesions of rainbow trout. Subcutaneous injection of the live organism into healthy frogs caused a condition typical of redleg disease, followed by death, and its subcutaneous injection into healthy rainbow trout caused the formation of large, necrotic, swollen areas filled with fluid. The organism was re-isolated from the deliberately infected animals and histological examinations showed a high degree of destruction of the muscular tissue in the affected areas. The pathogenic effect observed was apparently due to the extracellular bacterial proteinase. Growth of the pseudomonad was insignificant at 3 °C and 37 °C, was slight at 8 °C, and optimal between 15 and 25 °C, and the culture filtrates possessed strong proteolytic activity against casein, hemoglobin, and rainbow trout muscle albumin. The production of this proteinase was dependent on the growth of the organism and the composition of the growth medium.