Fig 3.

Doxycycline converts fluconazole from fungistatic to fungicidal and prevents the onset of drug resistance. (A) Viable cell counts after 48 h or 96 h of incubation in the presence of fluconazole alone or with 50 or 100 μg/ml doxycycline added. Open symbols, viable cell counts after 48 h of incubation; filled symbols, viable cell counts after 96 h of incubation. Circles, fluconazole alone; squares, fluconazole plus 50 μg/ml doxycycline; triangles, fluconazole plus 100 μg/ml doxycycline. Values falling below the detection limit of 10¹ CFU/ml were approximated to 0.5 × 10¹ CFU/ml. Mean values from three independent experiments are shown. (B) Emergence of fluconazole-resistant strains on plates containing 128 μg/ml fluconazole without (top) or with (bottom) 50 μg/ml doxycycline. Plates were incubated for 4 days before being scanned.