Competitive indices of <i>S</i>. Typhimurium 4/74 wild type bacteria relative to mutant bacteria in the mouse spleen.

C57/BL6 mice were infected i.p. with equal numbers of mutant and wild type bacteria (each 5×103 CFU). After 4 to 6 days, mice were sacrificed and the spleen was removed. Serial dilutions were spotted on LB agar plates and number of wild type and mutant bacteria in a total of 100 colonies was further determined by selection of the resistance marker. Competitive indices (C.I.) were calculated as previously described [42]. The results are shown as mean values ± STD based on the number of mice tested as indicated in brackets. Significant differences from 1.0 (**p<0.01) were determined by one-sample t-test analysis.