The haemolytic activity of Haemophilus species.

The importance of the species of blood employed for detection of haemolysis in seventy-seven Haemophilus strains of human and porcine origin was studied. Significant differences in the visibility of haemolytic zones obtained on the different blood agar media were observed. In decreasing order, the suitability of the species of blood was: calf, sheep, human, rabbit, poultry and horse blood. On plates containing washed sheep or calf red cells the haemolysin of all 36 strains of Haemophilus pleuropneumoniae acted synergistically with the beta-toxin of the Staphylococcus aureus strain used as "feeder strain", giving rise to a lytic phenomenon resembling the CAMP reaction.