Figure 4. In vivo competition between the ΔT6SS_SPI-6 mutants complemented in trans with T6SS_SPI-6 or T6SS_SPI-19 and the wild type S. Typhimurium 14028 s.

Fifteen four-day-old White Leghorn chicks were orally infected with 10⁹ CFU of a mixture at a 1∶1 ratio of strains WT/R995, ΔT6SS_SPI-6/R995+SPI-6 and ΔT6SS_SPI-6/R995+SPI-19. At 1, 3 and 9 days post-infection groups of five chicks were sacrificed and the organs were excised, homogenized, and serially diluted for determination of bacterial loads. Bars represent the geometric mean of the log converted ratio of the mutant CFU to the wild type CFU normalized to the equivalent ratio in the inoculum. Error bars denote standard error. Statistical significance was determined using a two-tailed Student’s t test, and asterisks indicate statistically significant differences between normalized output ratios (*P<0.05). ^‡Indicate statistically significant differences between normalized output ratios and the equivalent ratio in the inoculum (^‡ P<0.05).