Fig. 9

Mechanism of sequential activation of Salmonella infection and regulation pathways. HilA is the central regulator of SPI-1 and T3SS needle apparatus in association with the host cell. Salmonella invasion proteins (Sips), A–D mediate SPI-1 effectors secretion and translocation. After translocation into host cells, the Salmonella outer proteins (Sops) are involved in polymorphonuclear leukocyte influx. After crossing the epithelial barrier, T3SS encoded SPI-2 effector proteins are secreted into the cell's cytosol for gene expression. The pathogen first recognizes these influence factors in the distal gut lumen and later in the intra-macrophage environment