To verify this, in the next step we constructed two additional mutants - the first one without both the SPI-1 and SPI-2 (ΔSPI1&2 mutant) and the second one with only the SPI-1 and SPI-2 retained (SPI1&2o mutant), and we repeated the infections including the wild-type S. Enteritidis strain and S. Enteritidis ΔSPI1-5 mutant as controls. This evidence concerns the gene SPI1 and infection.