Resistance of Candida albicans to direct lethal miconazole action induced by low-level miconazole.

Logarithmic phase cells of Candida albicans are susceptible to physicochemical damage by greater than or equal to 2 x 10(-5)mol miconazole resulting in direct lethal action (DLA). Stationary phase yeasts are resistant to such action. At low levels (i.e. less than 10(-5)mol), miconazole can inhibit synthesis of cell membrane components and can also revert DLA-susceptible cells to DLA resistance. Reversion was studied in relation to low-level miconazole exposure time. DLA was assessed by viable count determinations. Most cells in susceptible cultures reverted to resistance within 30 to 60 min of exposure to 2.0 x 10(-6)mol miconazole. The rapidity of this shift suggested subtle alterations in existing cell membrane material in response to low-level miconazole. Saturation of membrane fatty acids might explain the shift.