Production of Small-Colony Variants of Staphylococcus aureus.

Abstract

We have previously reported the production of small-colony variants, or G forms, after prolonged serial transfer of S. aureus in lithium chloride broth or plain broth media.1, 2 Swingle3 subsequently confirmed these results and also obtained these forms after extended growth in nutrient broth or casein-digest medium. Under these conditions the variants occur only rarely and in small numbers, seldom exceeding 1.0% of the colonies on a plate. Chinn4 in a study of the metabolic activity of the small colony variants of S. paradysenterio Sonne and S. aureus found them to be metabolically far less active than the normal forms, having a reduced generation-time, reduced fermentative powers, lessened ability to reduce methylene blue and a slower cataphoretic velocity. This lowered metabolic activity and the ability to revert to forms identical with the parent culture furnishes some evidence that small-colony variants may be forms whose metabolism has been greatly reduced by some unknown factor.Quastel and Woolridg...