FIG. 4.

Effect of ExoS production on HT-29 cell re-adherence. HT-29 cells were cocultured with 10⁸ CFU of bacteria per ml for 3 h (MOI of 30:1); bacteria were then removed, and cells were detached by trypsin-EDTA treatment and reseeded in culture wells. At 20 h, adherent and nonadherent cells were harvested separately, cell viability and numbers were assessed by trypan blue staining, and DNA synthesis was assayed as described in Fig. 1. Viability is expressed as the percentage of total adherent plus nonadherent cells, and the means and standard errors of three independent assays are shown. DNA synthesis, indicated in brackets above bars, is reported as the disintegrations per minute per 1,000 cells in the respective adherent or nonadherent populations. Results of one of three independent DNA assays are shown, and the mean of assays performed in triplicate is represented.