Figure 5: The optimized PMA assay distinguishes cell viability state in the presence of white powders. ΔCT values remain consistent in viable and nonviable Y. pestis pgm- (A) and B. anthracis Sterne (B) cells in the presence and absence of white powders. Signal reduction is calculated as the difference in CT value of a sample that was not exposed to PMA and a sample pretreated with PMA. Measurements are the average value of three independent experiments and error bars are representative of the standard deviation. The * symbol indicates a statistically significant difference (p < 0.05) when comparing the ΔCT values of viable and nonviable populations. Among the three independent experiments, the total number of cells per qPCR reaction for B. anthracis Sterne ranged from 8.01 × 104 to 3.97 × 105 which corresponded to CT values of 21.7 to 22.9 For Y. pestis, the total number of cells per qPCR reaction ranged from 1.42 × 106 to 1.99 × 106 which corresponded to CT values of 14.8 to 14.9.