In accordance with these results, immunostaining (Fig. 2D), plating of isolated epithelial cells after gentamicin-treatment to remove extracellular Salmonella (Fig. 2E–F) and flow cytometry (Fig. 2G) detected enterocytes infected by WT but not SPI1-deficient Salmonella. Both, WT and ΔinvC Salmonella after high and low dose infection spontaneously colonized the intestinal tract (Fig. S2A–C). This evidence concerns the gene SPI1 and infection.