MODE OF ACTION AND RESISTANCE TO AZOLE ANTIFUNGALS ASSOCIATED WITH THE FORMATION OF HA-METHYLERGOSTA-8,24(28)-DIEN-3-BETA,6-ALPHA-DIOL

Azole antifungal compounds inhibit sterol 14 alpha-demethylase. They a re used extensively for the treatment of immunocompromised patients wh ere fungal infection is common and often results in death. Resistance to the compounds is emerging, particularly in fungal pathogens obtaine d from AIDS patients undergoing prolonged therapy. We show here that c ell growth arrest correlates with the accumulation of 14 alpha-methyl- ergosta-8,24(28)-dien-3 beta,6 alpha-diol in a yeast strain with a ste rol 14 alpha-demethylase gene disruption, which mimics stringent treat ment conditions. Cells can overcome the effect of such a block by a su ppressor mutation in sterol Delta(5,6) desaturation and acquire azole resistance. Plasmid-based complementation of the sterol 14 alpha-demet hylase defect does not alter the azole susceptibility of strains conta ining these suppressor mutations, showing resistance is due entirely t o the Delta(5,6) desaturase defect. (C) 1995 Academic Press, Inc.