FIG 2.

TcdB causes a loss of membrane integrity faster than TcdA. YAMC cells at 37°C were intoxicated with the indicated concentrations of TcdA or TcdB and incubated at 37°C for 2 h (A), 4 h (B), 8 h (C), and 24 h (D). LDH release was measured using CytoTox Glo and normalized to that for the unintoxicated controls. Data were analyzed by two-way ANOVA at each time point. At 2, 4, and 8 h, there was a significant difference between TcdA and TcdB at concentrations of ≥100 pM (*, P < 0.0001). There was no significant difference at concentrations of ≤10 pM. At 24 h, two-way ANOVA revealed no significant difference between TcdA and TcdB at any concentration tested. Data represent the averages from three experiments performed in triplicate. Error bars represent the standard deviations of the means.