In contrast, the SPI-1-deficient bacteria (tetR), induced to enter independent vacuoles through bystander infection with wild-type Salmonella (tetS), as measured by tetR colony-forming units or immunofluorescence, were unable to replicate in host cells of either genotype and were never released in the cytosol (Figures 3A, 3B, and S5) [35]. This evidence concerns the gene SPI1 and infection.