Figure 6.

Checkerboard assays of compounds pentamidine (1), 21, 22, and 23b in combination with (A) rifampicin and (B) novobiocin against E. coli BW25113. In each case, the bounded box in the checkerboard assays indicates the combination of the compound and antibiotic resulting in the lowest FICI (see Table 2). OD₆₀₀ values were measured using a plate reader and transformed into a gradient: purple represents growth, white represents no growth. The poor aqueous solubility of novobiocin results in the background signal observed in the OD₆₀₀ read-out at when tested at concentrations ≥100 μg/mL. An overview of all checkerboard assays with rifampicin, novobiocin, and vancomycin can be found in Supporting Information, Figures S2–S4.