FIG. 5.

Serum anti-toxin A antibody levels following oral immunization against C. difficile toxoid A. Mice were immunized with formalin-inactivated toxoid A (TxA) administered by gavage on days 0, 7, 14, and 21 and were sacrificed on day 35. Some mice received cholera toxin (CT; 10 μg) administered by gavage with toxoid A. Other mice received toxoid A by gavage and S. boulardii (Sb) in their drinking water (3 × 10⁸ CFU per ml). Serum IgA, IgG, and IgM anti-toxin A levels were measured by ELISA. Results are expressed as optical density (O.D.) units (×1,000 for IgA and ×100 for IgG and IgM) (mean and standard error; n = 9 for each treatment group). Serum IgM anti-toxin A levels were higher in the Sb plus TxA group compared to the control (P = 0.002 by ANOVA). There were no other statistically significant differences between any of the treatment groups.