Figure 2.

Standard microdilution test and survival curves of Y. pestis Kimberley53 exposed to ciprofloxacin. A culture of MHB-suspended Y. pestis Kimberley53 was prepared from BHIA-plated bacteria to a standard inoculum size of 5 × 10⁵–1 × 10⁶ CFU/ml and incubated for 2 h at 28°C with moderate agitation (for adjustment of the culture from the BHIA to MHB growth medium) before performing the 24-h microdilution test. (A) The microdilution test was conducted in a 96-well microplate at the indicated ciprofloxacin concentrations, and the OD₆₃₀ was measured hourly using a TECAN plate reader. (B) Survival analysis was performed by BHIA plating of serial 10-fold dilutions of replicate samples at different time points after ciprofloxacin addition. The error bars represent the SD of 3 independent experiments.