FIG. 4.

Sandwich ELISA detection of untreated versus gamma-irradiated B. anthracis spores. Untreated and irradiated B. anthracis strain K1694 (Ames) spores at concentrations ranging from 10¹ to 10⁷ CFU/ml were detected by sandwich ELISA using the PAb for capture and the MAb for detection. The results were plotted as the mean optical density (OD) or absorbance of triplicate wells at 450 nm minus the background ± standard error of the mean (error bars). The differences between untreated versus irradiated spores were not found to be significant using a paired t test (two tailed) (P = 0.56; n = 21).