Weakly beta-haemolytic human intestinal spirochaetes antagonize the haemolytic activity of Clostridium perfringens alpha-toxin producer

The production of haemolytic antagonism between weakly beta -haemolytic hum an intestinal spirochaetes (w beta HIS) related to human intestinal spiroch aetosis and Clostridium perfringens alpha -toxin producer was investigated. A reduction of the clostridial haemolytic activity and a distortion of the haemolytic halo of clostridial alpha -toxin surrounded by a small zone of poorly cooperative haemolysis was clearly observed on the level of the spir ochaetal growth area when 40 out of 41 w beta HIS were cultivated in sheep blood agar plates together with Clostridium perfringens alpha -toxin produc er. This phenomenon of haemolytic antagonism was observed only when w beta HIS grew 72-96 hours sooner than C. perfringens and after the inoculum of t he latter at a distance of 0 to 10 mm from w beta HIS the plates were anaer obically incubated for an additional 48 hours and the bacteria were used at concentrations ranging from 10(7) to 10(4) CFU/ml. These results were also observed between C. perfringens and weakly beta -haemolytic intestinal spi rochaetes related to animal intestinal spirochaetosis including avian strai ns and Brachyspira (Serpulina) pilosicoli of porcine origin.