Fig 6. D23580 is less fit than 4/74 in the chick embryo model.
S. Typhimurium 4/74 and D23580 at 16 hours post-infection with 102 CFU bacteria. Competitive index in yolk (A) and liver (B). Competitive index values were calculated as the ratio of D23580 to 4/74 recovered from the yolk or liver, divided by the ratio of D23580 to 4/74 present in the inoculum. The numbers of each strain were quantified by plating dilution series on LB agar using antibiotic resistance to distinguish between strains. Counts are shown as individual embryos with the bar representing the median value. Ten and eight embryos were used to measure the competitive index in yolk and liver respectively. Statistical comparison was made using a t-test and shows that CI values were statistically different from 1.0.