Cooperative haemolysis between weakly beta-haemolytic human intestinal spirochaetes and Staphylococcus aureus

Weakly beta-haemolytic spirochaetes related to human intestinal spirochaetosis produced a cooperative haemolysis together with S. aureus consisting of an enhanced haemolysis in the zone of the spirochaetal growth which was overlapped by the zone of activity of the staphylococcal beta-haemolysin. The cooperative haemolysis was observed in sheep blood agar media when the concentration of spirochaetes ranged from 1.5 x 10(3) to 1.5 x 10(8) CFU/ml and the concentration of S. aureus from 4 x 10(3) to 4 x 10(8) CFU/ml. With the increase of the distance between the streaks of the spirochaetes and S. aureus from 3 to 10 mm, the period of incubation needed to observe the cooperative haemolysis also increased from 18 to 72 hours. When the spirochaetes and S. aureus were streaked at the same time and when S. aureus was streaked earlier than the spirochaetes, the phenomenon was observed after anaerobic incubation of the plates for 24-72 hours but not after incubation in 10% CO2 under atmospheric conditions. A cooperative haemolysis was also observed between S. aureus and spirochaetes related to the porcine and avian intestinal spirochaetosis and the spirochaete causing swine dysentery when the same experimental conditions were used which allowed an observation of the phenomenon involving human spirochaetes and S. aureus.