Figure 1. Staphylococcus aureus small colony variants (A) and S. aureus with a normal phenotype (B) cultured on sheep blood agar after 24 hours of incubation at 35°C. Staphylococci were identified by conventional methods (6) and with the ID 32 Staph system (bioMérieux, Marcy-L'Etoile, France) following the instructions of the manufacturer. The tube-coagulase test was read after 24 hours. S. aureus isolates were characterized as small colony variants as described before (7-8). Auxotrophic requirements were evaluated with 10-µg hemin disks, 1.5-µg menadione disks, and 1.5-µg thymidine disks on Mueller-Hinton agar and on chemically defined medium (CDM) agar as well as on CDM agar supplemented with 1 µg/mL hemin, 100 µg/mL thymidine, and 1 µg/mL menadione, respectively.