Growth requirements of some small-colony-forming variants of Staphylococcus aureus

Nine stable, auxotrophic, small-colony-forming variants of Staphylococcus aureus were isolated. They were of two types. One type, from broth cultures containing varying concentrations of gentamicin or kanamycin, required heme for normal growth. The second type, from the blood culture of a patient who had been treated with penicillin and oxacillin, required long-chain unsaturated fatty acids for normal growth. These small-colony-forming variants differed from their parents with respect to specific metabolic activities, many of which may be attributed to an impaired electron transport system and related functions. A laboratory procedure for detecting possible small-colony variants in clinical specimens was proposed.