Small Colony Variants and Senescent Bacteria

Small colony variants (SCVs) are bacterial subpopulation that grow slowly and form smaller colonies. They have been described for a wide range of bacterial species, but most extensively studied for Staphylococci. They are considered as mutants that are auxotrophic to hemin, thiamine or thymidine. In the presence of auxotrophic agents, they revert to normal growth. They are tolerant to many antibiotics and are implicated in chronic and persistent infections. In this presentation, it is proposed that most of them are normal senescent bacteria that do not revert in the presence of auxotrophic agents. SCVs can explain the concentration dependent killing property, long post-antibiotic effect and increased resistance to aminoglycosides