FIG. 1.

S. suis isolate grown on sheep and human blood agar plates at 37°C in the presence of 5% CO₂. After 24 h of incubation, small colonies are visible, which appear as alpha-hemolytic viridans streptococci on sheep blood agar plates (A) and as beta-hemolytic streptococci with a clear halo of hemolysis around the colonies on human blood agar plates (B). After prolonged incubation for 48 h, large colonies are visible with clear beta-hemolysis on both sheep (C) and human (D) blood agar plates. Hemolysis after prolonged incubation is more pronounced. Arrowheads indicate beta-hemolysis.