Conditions for in vitro haemolytic activity by Corynebacterium ovis exotoxin

A substance, concluded to be Corynebacterium ovis exotoxin on the basis of properties shared, was found to have haemolytic activity below pH 6 and red cell adhesion activity at neutral or slightly alkaline pH. An acidified, solid blood agar medium was used to demonstrate the extent of haemolysis that could be obtained at optimal pH and its inhibition by immune serum. Culture in a liquid medium giving rise to a suitably acidic pH allowed titration for haemolytic activity by the exotoxin and use of supernatant in a haemolysis-inhibition test to detect antitoxin.