Printed in Great Brituin 20 r

Polyene antibiotics act by combining with sterols in the membrane of susceptible organisms, and thereby affect permeability. Recent studies have indicated that polyene resistance may be associated with altered sterol patterns in Candidu spp. (Athar & Winner, 1971), quanti-tatively, and in Saccharomyces cerevisiae (Thompson, Starr & Parks, 1971; Woods, 197r), quantitatively and qualitatively. Following the recent isolation (Hamilton-Miller, I 972) of a new type of polyene-resistant Candida albicans mutant (mutagen-induced), the sterol contents of such mutants were compared with that of the parent strain. M E T H O D S A clinically isolated Candida albicans strain (799-S) was treated with N-methyl-"nitro-N-nitrosoguanidine, and four polyene-resistant mutants, 799-x ~ , -XS,-YL and-YS, were isolated (Hamilton-Miller, I 972). Organisms were grown on Sabouraud agar contained in 14 cm Petri plates (two plates for each strain), inoculated with 2 ml amounts of Sabouraud broth overnight cultures and incubated at 37 "C for 48 h. Organisms were washed off the plates, washed with water and then homogenized in an equal volume of water (2 to 3.5 ml); I ml amounts of the resulting suspensions were removed for dry weight determinations, an