Although MICs obtained with CDC anaerobe agar and brucella blood agar were identical, we noticed one difference between the two agar types. Some P. acnes strains were strongly hemolytic on brucella blood agar, but these strains did not show hemolysis on CDC anaerobe agar, even though both agars contain 5% sheep blood. P. acnes strains showing hemolysis on brucella blood agar appeared to have a more aggressive clinical course than the nonhemolytic strains. Our investigation of the role of hemolysis in P. acnes is being submitted for publication elsewhere.