Gladiolin synergizes with AmpB against multiple priority fungal pathogens. (A) Chemical structure of gladiolin. Heatmaps of checkerboard assays of gladiolin in combination with (B) amphotericin, (C) fluconazole, and (D) caspofungin. Shown here are the data for the reference strain SC5314, while an additional 20 clinical isolates are shown in Fig. S2A. (E) Heatmap of gladiolin/AmpB checkerboard assays for C. auris 470140 (clade I). Additional C. auris clades are shown in Fig. S2B. (F) Heatmap of gladiolin/AmpB checkerboard assay for C. glabrata ATCC2001. (G) Heatmap of gladiolin/AmpB checkerboard assays for C. neoformans H99. For all checkerboard experiments, fungal cultures were grown in RPMI, pH 7.0, and cell density at 600 nm was measured at 20 h of growth at 37°C for all Candida species and at 48 h for Cryptococcus. The color scale shows the percentage of survival compared to untreated control. The fractional inhibitory concentration index (FICI) is indicated as white numbers and is defined as <0.5 (synergistic), >0.5 to <1 (additive), 1–4 (indifferent), and >4 (antagonistic). Heatmaps and FICIs were derived from mean values of 3–4 biological repeats.