Table 1. List of bacterial strains used in this study.

Bacterial strain	Short name	Properties	Source
E. coli DH5α	DH5α	F-, ϕ80dlacZΔM15, Δ(lacZYA-argF)U169, deoR, recA1, endA1, hsdR17(rK −, mK +), phoA, supE44, λ−, thi-1, gyrA96, relA1	Invitrogen
S. Typhimurium SL1344	SL1344	A wild-type S. Typhimurium strain, streptomycin resistant	Dr. B. Finlaya
S. Typhimurium SL1344 ΔssaR	ΔssaR	SL1344 missing the ssaR gene from SPI-2	Dr. B. Finlaya
S. Enteritidis Sal18	Sal18	Virulent for birds, invades liver and spleen, and colonizes gut	Dr. C. Poppeb
S. Enteritidis Sal18 ΔSPI-2::cat	ΔSPI-2::cat	Sal18 with the whole SPI-2 region deleted and replaced by a chloramphenicol resistance gene using the λRed system.	[24]
S. Enteritidis Sal18 ΔSPI-2	ΔSPI-2	Derivative of Sal18 ΔSPI-2::cat with the chloramphenicol resistance gene deleted using the λRed system.	[24]

^aDr. B. Finlay, University of British Columbia, Vancouver, British Colombia.

^bDr. C. Poppe, Laboratory for Foodborne Zoonoses, Health Canada, Guelph, Ontario.