Plasmid-mediated trans- complementation of the Δ pegA :: cat mutant of S . Enteritidis P125109 at 1 and 3 days post-oral inoculation of 18-day-old out-bred Rhode Island Red chickens. Total caecal load of the wild-type and mutant strain were compared to those of the P125109 ΔpegA::cat insertion mutant and ΔpegA strains in which pegA was introduced on plasmid pACYC177 in either the forward or reverse orientation relative to the promoter of the kanamycin resistance gene. The data represent the mean total caecal load ± standard error of the mean from five birds at each time interval for each strain. The dashed line indicates the theoretical limit of detection by direct plating (2.2 log10 CFU/g). F-tests of the difference in recovery of wild-type and mutant strains at each time interval were performed and P values < 0.05 are marked with an asterisk.