Staphylococcus aureus small colony variants, electron transport and persistent infections

Staphylococcus aureus can mutate to form a sub-population of bacteria known as small colony variants (SCVs). These bacteria have a characteristic phen otype defined by slow growth, the lack of pigment, an altered pattern of ca rbohydrate utilization, and a reduction in toxin production. This complex p henotype can be explained by deficiencies in electron transport. In clinica l isolates, the most common mutations that affect electron transport are in the operons encoding menaquinone or heme biosynthesis. These isolates are responsible for persistent antibiotic resistant infections. The clinical pr esentation of these infections is readily explained by a reduction electron transport. SCVs survive within host cells, increasing the instances of rec urrent infections and have a novel mechanism of resistance based upon their altered trans-membrane potential. Additionally, SCVs provide a connection between energy metabolism and toxin production. This link may operate throu gh the bacteria responding to altered levels of NADH and ATP. A more comple te understanding of these signaling pathways may provide new targets for th e development of drugs to ameliorate staphylococcal virulence and disease. (C) 2000 Elsevier Science B.V. and International Society of Chemotherapy. A ll rights reserved.