Resazurin sodium (Diazoresorcinol sodium) is commonly used to measure bacterial and eukaryotic cell viability through its reduction to the fluorescent product resorufin. No viable bacteria are detected 24 h post-inoculation following inclusion of Resazurin sodium in TSBc cultures of F. tularensis LVS at the concentration of 44 μM. Lowering the Resazurin sodium concentration to as little as 4.4 μM still results in a 10-fold reduction in viable F. tularensis LVS compare to growth medium alone. Both Resazurin sodium treatments result in a significant decrease in viable F. tularensis LVS bacteria over 22 h. Treatment with Resazurin sodium significantly reduces the number of viable F. tularensis LVS bacteria in HEK293 cells 22 h post-infection.