PERSISTENT AND RELAPSING INFECTIONS ASSOCIATED WITH SMALL-COLONY VARIANTS OF STAPHYLOCOCCUS-AUREUS

Small-colony variants (SCVs) of Staphylococcus aureus were cultured fr om five patients with persistent and relapsing infections, All five SC V strains were nonhemolytic and nonpigmented and grew very slowly on r outine culture media in an ambient atmosphere, In several instances, t hese phenotypic characteristics led to the initial misidentification o f the organisms in the clinical microbiology laboratory, All four stra ins available for further analysis were shown to be auxotrophs that re verted to normal growth and morphology in the presence of menadione, h emin, and/or a CO2 supplement, Similarly, these isolates were resistan t to aminoglycosides under routine conditions but susceptible in the p resence of the metabolic supplements, For two patients, the large and small colony forms isolated concurrently were indistinguishable when a nalyzed by pulsed field gel electrophoresis and thus represented pheno typic variants within individual clones, We propose a model relating t he phenotypic characteristics of S. aureus SCVs with the clinical patt ern of persistent and relapsing infection.