Density of attachment of <i>B. pilosicoli</i> cells to Caco-2 cells after 2, 4 and 6 h incubation.^*

*Results are derived from 12 fields of view. They are median (and the range) at each time point, where 0 represents no attachment observed and 5 represents the entire surface of the field covered with spirochetes such that the Caco-2 cell surface was not visible.