RPMI Medium for E-Test RPMI Medium is recommended for use in anti-fungal susceptibility testing of yeasts from clinical isolates using the E-Test method. The medium is based on a simple Glucose Agar with added RPMI-1640 Medium (without Sodium Bicarbonate & Phenol Red), which supplies the necessary vitamins and amino-acids, and MOPS (3-(Morpholino)propanesulfonic Acid) Buffer to maintain the medium pH during incubation.