Studies on Small Colony Variants of Staphylococcus aureus

Abstract

Several such variants were isolated from old broth or agar cultures or from cultures in LiCl broth. The colonies were usually about 0.1 mm. in diam. and lacked pigment. The cells were either similar to the normal or showed marked irregularities in size. The small colony strains had lost the ability to ferment lactose and sucrose, and their rate of multiplication in broth was many times slower than that of the normal form. They were avirulent for rabbits. All attempts to demonstrate the association of a filterable stage with these organisms were unsuccessful. Agglutination tests showed most of the variants to be antigenically similar to their source strains. Reversion to the normal form occurred occasionally on agar and could be enhanced by aging in broth or by enrichment of the media.