CHARACTERIZATION OF HEMOLYTIC-ACTIVITY FROM AEROMONAS-CAVIAE

Aeromonas caviae, an enteropathogen associated with gastroenteritis, d isplays several virulence characteristics. Studies on the kinetics of growth of A. caviae and expression of beta-haemolytic toxin revealed t hat A. caviae produced maximum haemolytic activity extracellularly dur ing the stationary phase. Preliminary studies on the properties of A. caviae haemolysin suggested that divalent cations (Mg2+ and Ca2+) and thiol compounds, dithiothreitol and mercaptoethanol enhanced the haemo lytic activity. Addition of L-cysteine, glutathione and EDTA reduced t he haemolytic activity. The iron chelator, 2-2' bipyridyl, significant ly inhibited the growth of A. caviae possibly by iron limitation, with parallel enhancement of haemolysin production compared to A. caviae g rown in excess of iron. These results suggest that A. caviae produces only beta-haemolysin, which resembles the haemolysins reported for sev eral other bacteria and the activity might be regulated by environment al factors especially iron.