FIGURE 1.

Construction of a surrogate panel of antibiotic resistant Francisella. (A) Schematic of experimental design. Serial passaging of LVS and Fn was performed on increasing concentrations of ciprofloxacin or streptomycin, alternating between broth and agar. Concentration gradients of each antibiotic are shown from low to high (light blue to dark blue), and dotted lines indicate endpoints for either Fn or LVS passaging. At each endpoint, 10 isolated colonies of either LVS or Fn CipR or StrepR were passaged 10 times without the presence of antibiotic to confirm resistance stability and sequenced. (B) Antibiotic concentrations used in each selection step of Fn (left graph) and LVS (right graph) during passaging with ciprofloxacin and streptomycin. Note that LVS required additional intermediate steps of selection on ciprofloxacin, resulting in the 22 selection steps shown.