Virulence of Staphylococcus aureus small colony variants in the Caenorhabditis elegans infection model

Small colony variants (SCVs) of Staphylococcus aureus are slow-growing morphological variants that have been implicated in persistent, relapsing, and antibiotic-resistant infections. The altered phenotype of SCVs in most strains has been attributed to defects in electron transport due to mutations in hemin or menadione biosynthesis. The pathogenic capacity of SCVs compared to phenotypically normal strains is variable depending on the attribute examined, with some studies showing reduced virulence of SCVs and others demonstrating normal or heightened virulence. Recently, the nematode Caenorhabditis elegans has been successfully employed as an alternative host to investigate virulence mechanisms of a variety of bacterial pathogens, including S. aureus. In this study, we show that clinical SCVs as well as hemB- and menD-deficient mutants of S. aureus are greatly reduced in virulence in the C. elegans infection model.