STAPHYLOCOCCAL SMALL COLONY VARIANTS HAVE NOVEL MECHANISMS FOR ANTIBIOTIC-RESISTANCE

Over the past 4 years, a variant subpopulation of Staphylococcus aureu s has been characterized that is defective in electron transport. Thes e organisms grow slowly and are typical of the previously described sm all colony variants (SCVs). Indeed, many earlier papers included data that are consistent with defective respiratory activity in SCVs. We pr esent a hypothesis that serves as biochemical basis for the developmen t of SCVs. These variants are particularly interesting because they ha ve been associated with very persistent infections, and they are more resistant to many antibiotics than normal S. aureus. Because of their slow growth, atypical colonial morphology, and unusual biochemical pro file, they are easily missed or misidentified in the clinical laborato ry. This is of some significance, as this subpopulation is more resist ant to antibiotics than the parent population from which they arose. W hen an infection is particularly resistant to therapy, persists for a long period, or fails to respond to apparently adequate antimicrobial therapy, clinicians and clinical laboratory personnel should consider special efforts to search for SCVs.