Growth of S. aureus and S. pneumoniae on selective media after replica plating from cocultures. Columns of the plate contain twofold dilutions of the staphylococcal strain beginning with 10⁸ CFU/ml in the left column. Rows contain twofold dilutions of the streptococcal strain beginning with 4 × 10⁷ CFU/ml. The right column contains the staphylococcal strain only, and the bottom row contains the streptococcal strain only. The bottom right corner well contains uninoculated BHI. A and B—S. aureus (Newman) after 0 and 6 h, respectively, grown on selective medium (tryptic soy agar supplemented with 5 μg/ml optochin); C and D—S. aureus (Newman) after 0 and 6 h in coculture supplemented with catalase (anaerobic conditions yielded identical results to those shown in panels C to D); E and F—S. pneumoniae (Pn-20) after 0 and 6 h, respectively, grown on selective medium (tryptic soy agar supplemented with 5% sheep blood and 8 μg/ml gentamicin).

S. aureus growth (A) in coculture with S. pneumoniae under aerobic conditions (▴), coculture in anaerobic conditions (⧫), coculture with periodic addition of catalase (▵), or plain BHI (•). (B) In sterile supernatant from S. pneumoniae cultures (▪), in supernatant with catalase supplementation (□), in plain BHI (•), or in BHI supplemented with catalase (○).