SPI1 and infection: In addition, through i.p infection of mice, we found that loiA did not confer an additional virulence defect by influencing systemic infection in a SPI-1 mutant background, since mice i.p. infected with the SPI-1 mutant or SPI-1/loiA double mutant also resulted in similar bacterial burdens in the livers and spleens (S5A and S5B Fig).