Siderophore, hemolytic, protease, and pyrazinamidase activities and antibiotic resistance in motile Aeromonas isolated from fish

A total of 120 fresh water fish samples were evaluated for the presence of Aeromonas spp. A. hydrophila, A. caviae, and A. veronii bv. sobria were isolated from the gills, intestines, livers, and skins of fish, and 78 isolated Aeromonas spp. strains were further examined for siderophore, hemolytic, protease, and pyrazinamidase activities and antibiotic resistance. Siderophore production was demonstrated in almost all of the A. hydrophila and A. caviae strains except for 2 strains of A. veronii bv. sobria. The strains identified as A. hydrophila and A. veronii bv. sobria were the stronger producers of hemolysin, whereas the A. caviae strains were nonhemolytic. It was found that 92% of A. hydrophila and 91% of A. caviae strains hydrolyzed pyrazinamide in under 48 h, whereas 5% of A. veronii bv. sobria strains hydrolyzed pyrazinamide. Protease activity was found in 100% of isolates of A. hydrophila and A. veronii bv. sobria, but in 81% of A. caviae isolates. In addition, all Aeromonas species were examined for antibiotic resistance patterns and were found to be resistant to ampicillin and tetracycline.