In vivo competition experiment between ∆T6SS
deletion mutant and wild type Salmonella Dublin strain CT_02021853 in orally infected chicks. Fifteen four-day-old White Leghorn chicks were infected intragastrically with 109 CFU of a 1:1 mixture of the mutant strain and wild type Salmonella Dublin CT_02021853. At 1, 3 and 9 days after the inoculation, 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 the normalized output ratio and the equivalent ratio in the inoculum. ** P value < 0.001; * P value < 0.05.