Characterisation of haemolytic activity fromAeromonas caviae

Abstract

Aeromonas caviae, an enteropathogen associated with gastroenteritis, displays several virulence characteristics. Studies on the kinetics of growth ofA. caviaeand expression of β–haemolytic toxin revealed thatA. caviaeproduced maximum haemolytic activity extracellularly during the stationary phase. Preliminary studies on the properties ofA. caviaehaemolysin suggested that divalent cations (Mg²⁺and Ca²⁺) and thiol compounds, dithiothreitol and mercaptoethanol enhanced the haemolytic activity. Addition of L–cysteine, glutathione and EDTA reduced the haemolytic activity. The iron chelator, 2–2' bipyridyl, significantly inhibited the growth ofA. caviaepossibly by iron limitation, with parallel enhancement of haemolysin production compared toA. caviaegrown in excess of iron. These results suggest thatA. caviaeproduces only β-haemolysin, which resembles the haemolysins reported for several other bacteria and the activity might be regulated by environmental factors especially iron.