FIG 10.

Anti-FliCD serum inhibits the adhesion of C. difficile to HCT8 cells. C. difficile R20291 vegetative cells (1.5 × 10⁶) in 100 μL BHI were preincubated with anti-FliCD hyperimmune serum (IgG titer 10⁷) at different serum dilutions (1/50, 1/100, 1/500 and 1/1,000) or with PBS/preimmune serum (1/50) for 30 min before being added to confluent HCT-8 cells (1 × 10⁵/well) in a 24-well plate in an anaerobic chamber. The plate was incubated at 37°C for 100 min. After incubation, the cell-R20291 mixture was washed three times with PBS via centrifugation to collect unbound R20291 cells. The percentage of R20291 adhesion was calculated using the following formula: (initial CFU/mL − unbound CFU/mL)/ initial CFU/mL. The experiments were independently repeated thrice. The data are presented as the mean ± SEM. (*, P < 0.05, versus treatment with preimmune serum).