Fig. (4) Non-clinical isolates of S. aureus growing in modified CRA (without sucrose) [A] and modified CRA containing sub-MICs of rifampicin (0.002 or 0.004 µg/mL) [B]. Identification of the isolates: H01, H03, H39, H43 and H56. Biofilm negative: spots with smooth appearance. Biofilm positive: spots with rough appearance.