RpoS integrates CRP, Fis, and PhoP signaling pathways to control Salmonella Typhi hlyE expression.

Background: SPI-18 is a pathogenicity island found in some Salmonella enterica serovars, including S. Typhi. SPI-18 harbors two ORFs organized into an operon, hlyE and taiA genes, both implicated in virulence.