Specificity and some physicochemical characteristics of the antibacterial activity from blue crabCallinectes sapidus

Haemolymph of the brachyuran crustaceanCallinectes sapiduspossesses bactericidal activity which is highly inhibitory to Gram-negative bacteria cultured from blue crab carapace, includingAeromonas hydrophila,Vibrio parahemolyticus,Vibrio alginolyticusandVibrio vulnificus. Several strains ofEscherichia coliwere also susceptible, but all other bacteria that were not isolated from blue crabs were resistant. No lysozyme-like activity was detected. A quantitative turbidometric assay usingE. coliwas used to measure antibacterial activity after exposure to various physical and chemical treatments. The activity was most active at low pH, heat-labile, inhibited by sodium chloride, and inactivated by protease. The antibacterial activity appeared to be confined to the haemocytes.