FIG 6.

Cytotoxicity of wild-type and mutant TcdB. Vero cells in 96-well plates were exposed to 1 or 10 ng/ml of TcdB, TcdB-L543A (LA), or TcdB-W102A D288N (aTcdB) for 1 to 4 days. Supernatants from each well were harvested, and LDH activity in supernatants was measured. The percentage of cytotoxicity was determined by the ratio of LDH release values to the maximum LDH release under the same treatment. The LDH release values represent the average of three experiments in which three replicates were averaged. Error bars indicate the standard errors among the values obtained from the three experiments.