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. 2016 Jan 28;7:37. doi: 10.3389/fmicb.2016.00037

FIGURE 3.

FIGURE 3

Inhibition of multidrug efflux does not reduce the resistance of F. tularensis LVS to Gm at 26°C. Bacteria were cultivated in general growth media, suspended in PBS, and treated with Gm, or Gm + PABN (25 μM Phenylalanine-Arginine Beta-Naphthylamide; efflux pump inhibitor) at the indicated temperature (A). Bacteria were diluted and plated for viable CFU at the indicated times. Plotted values represent mean CFU ± SD. F. tularensis LVS bacteria were subjected to disk diffusion assays in the presence or absence of PABN to show that this compound was capable of inhibiting multi-drug efflux (B,C) as reported for other bacteria F. tularensis LVS is known to utilize multidrug efflux to expel nalidixic acid (NA) and tetracycline (Tc). Disks contained 30 μg of the indicated antibiotic. Bars represent the mean of the zones of inhibition ±SE. Media containing PABN significantly increased the zones of inhibition produced by NA (B; ∗P < 0.0001, unpaired t-test) and Tc (C; ∗P = 0.0271, unpaired t-test) likely due to reduced efflux activity.