FIG 3.
The NAP1V strain induces a variant CPE. HeLa cells, Vero cells, and 3T3 fibroblasts were treated with TcdBNAP1 and TcdBNAP1V. Cells were treated until a CPE was achieved in 100% of the cells. Images obtained by phase-contrast microscopy show rounding as well as detachment of the cells caused only by TcdBNAP1V. In order to see actin cytoskeleton modifications, fibroblasts were stained with fluorescein isothiocyanate-phalloidin. TcdBNAP1-treated cells show a classical arborizing effect. TcdBNAP1V-treated cells that had not been detached were fixed and show cell rounding without an arborizing effect. Cells were visualized with a Nikon Eclipse 80i fluorescence microscope. Effects on cells induced by the toxins were visualized by scanning electron microscopy (SEM) using an S-3700N (Hitachi) electron microscope.