Autoagglutination of C. difficile strains. C. difficile strains were grown on BHI plates for 1 to 2 days, then inoculated into pre-equilibrated phosphate-buffered saline to an OD600 nm of 1.0 (± 0.1). These were incubated for 24 hours in pre-equilibrated glass tubes, then the OD600 nm was measured. The percentage of autoagglutination was normalized to the starting OD ((Starting OD - Final OD)/Final OD × 100). The bars indicate the percentage of cells autoagglutinating. Significant differences in autoagglutination are marked with an asterisk; P < 0.05, Students t-test. M120 is a non-motile strain thar autoagglutinates to a significantly higher level than 630 (P < 0.05).