Virulence and production of extracellular proteins (ECP) of Aeromonas hydrophila associated with the epizootic ulcerative syndrome (EUS) of freshwater fish

Abstract

Sixteen isolates of Aeromonas hydrophila isolated from normal, apparently normal and epizootic-ulcerative syndrome (EUS)-affected fish were screened for virulence and production of extracellular proteins (ECP). Results showed that all isolates were virulent to catfish (Clarias batrachus) juveniles inducing dermonecrotic lesions after intramuscular injection. Lesions were characterized by necrosis of the underlying musculature that leads to erosion and sloughing-off of the locally affected tissues. Only seven of the 16 ECP preparations, however, induced similar lesions on test catfish. No clear correlation between virulence and ECP production of EUS-associated A. hydrophila was established.