KKL-10 shows markedly antimicrobial activity against both fully and attenuated virulent strains of F. tularensis. The MIC against F. tularensis strain Schu S4 and LVS are 0.48 and 0.12 μg/mL, respectively. KKL-10 inhibits the intracellular growth of F. tularensis during all stages of infection. KKL-10 cannot affect macrophage function or viability. KKL-10 (17.5 μg/mL) produces cytotoxic effects of less than 5%. The combination of IFN-γ stimulation and KKL-10 can reduce the bacterial load by >99.9%. KKL-10 also inhibits the growth of F. tularensis inside eukaryotic cells and exhibits no toxicity to HepG2 cells.