Effect of cultural conditions on the presence of a cholera-toxin cross-reactive factor in culture filtrates ofAeromonas hydrophila

Culture filtrates ofAeromonas hydrophila isolate SSU were shown to contain an extracellular product that antigenically cross-reacts with cholera enterotoxin as determined by the enzyme-linked immunosorbent assay (ELISA). We have termed this extracellular product cholera-toxin cross-reactive (CTC) factor until further characterization is accomplished. Various cultural conditions were examined to determine maximum CTC factor production. The results indicate that optimal conditions for the highest levels of extracellular CTC factor produced byA. hydrophila grown in CYE broth occurred when cultures were incubated at 37°C with shaking at 100 rpm. CYE culture filtrates caused fluid accumulation in rabbit ligated intestinal loops. Heating the culture filtrates at 56°C for 10 min resulted in the loss of biological activity and antigenic integrity of the CTC factor as determined by the rabbit ligated intestinal loop assay and theELISA, respectively. The data presented in this study suggest that culture filtrate containing this molecule, or aggregate of molecules, may play a role in the pathogenesis ofA. hydrophila-mediated disease. Further studies including the purification of this factor(s) presently are being conducted in our laboratory.