Evaluation of the Synergistic Activity of Antibacterial and Antifungal Drugs against Candida auris Using an Inkjet Printer-Assisted Method.

Candida auris is an emerging multidrug-resistant fungal pathogen that spreads readily in health care settings and has caused numerous hospital outbreaks. Very few treatment options exist for C. auris infections. We evaluated the activity of all two-drug combinations of three antifungal agents (amphotericin B, caspofungin, and voriconazole) and two antibacterial agents (minocycline and rifampin) against a collection of 10 C. auris isolates using an automated, inkjet printer-assisted checkerboard array method. Three antibacterial-antifungal combinations (amphotericin B plus rifampin, amphotericin B plus minocycline, and caspofungin plus minocycline) demonstrated synergistic activity by checkerboard array against ≥90% of strains, with fractional inhibitory concentration index (FICI) values of 0.094 to 0.5. The two amphotericin B-containing combinations were also synergistic using the time-kill synergy testing method, with up to a 4.99-log10 decrease in surviving yeast compared to either agent alone. Our results suggest that combinations of antifungal and antibacterial agents provide a promising avenue for treatment of this multidrug-resistant pathogen.