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

The production of haemolytic antagonism between weakly β-haemolytic human intestinal spirochaetes (wβHIS) related to human intestinal spirochaetosis and Clostridium perfringens α-toxin producer was investigated. A reduction of the clostridial haemolytic activity and a distortion of the haemolytic halo of clostridial α-toxin surrounded by a small zone of poorly cooperative haemolysis was clearly observed on the level of the spirochaetal growth area when 40 out of 41 wβHIS were cultivated in sheep blood agar plates together with Clostridium perfringens α-toxin producer. This phenomenon of haemolytic antagonism was observed only when wβHIS grew 72-96 hours sooner than C. perfringens and after the inoculum of the latter at a distance of 0 to 10 mm from wβHIS the plates were anaerobically 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 β-haemolytic intestinal spirochaetes related to animal intestinal spirochaetosis including avian strains and Brachyspira (Serpulina) pilosicoli of porcine origin.