In vivo competition experiment between ∆T6SS
mutant complemented in trans with T6SS
and wild type Salmonella Dublin strain CT_02021853 in orally infected chicks. Fifteen four-day-old White Leghorn chicks were orally infected with 109 CFU of a 1:1 mixture of strains WT/R995, (∆T6SSSPI-6/∆T6SSSPI-19)/R995 + SPI-6 and (∆T6SSSPI-6/∆T6SSSPI-19)/R995 + SPI-19. At 1, 3 and 9 days post-infection, groups of five chicks were sacrificed and the cecum, liver and spleen were aseptically excised and homogenized in sterile PBS. Bacterial load recovered from each organ was determined by plating serial ten-fold dilutions on LB agar plates with the appropriate antibiotics. Bars represent mean values ± standard error. Statistical significance was calculated using the Student’s t test. Asterisks indicate the statistical significance of differences between data sets. ** P value < 0.001; * P value < 0.05.