Fig 7. PittII Msf-KO strain suffers a large competitive disadvantage compared to WT.

Competitive Index (CI) refers to a ratio of mutant bacteria to WT bacteria adjusted for the initial inoculum ratio. CI of 1 indicates no competitive advantage. Data points below 1 indicate a WT advantage and data points above 1 indicate a mutant advantage (A-D). (A) PittII WT and Msf-KO inoculated 1:1 in planktonic culture for 24 hours (3 experiments with n = 3, error bars denote the standard deviation of each experiment). (B) PittII WT and Msf-KO inoculated 1:1 in biofilm culture harvested over a 6 day period (3 experiments with n = 3, error bars denote the standard error of the mean). CFU were enumerated from both the adherent biofilms as well as the overlying supernatant and the CI was determined from each fraction. *p<0.05 by one-sample two-tailed t-test (μ₀ = 0) on the log CI for both the biofilm and planktonic fractions. (C-E) In two separate experiments six chinchillas were inoculated with 1:1 mixtures of strains and five tissue sites (brain, right and left bullar membranes and right and left bullar effusions) were harvested three days after inoculation. Thus n = 6 for brains and n = 12 for bullar sites. (C) In vivo competition between PittII WT and Msf-KO inoculated 1:1 into 6 animals. Each data point represents a single tissue-site CI value. Points on the X-axis (CI of 0) indicate that no KO bacteria were observed and therefore have an infinitely low CI value. (D) In vivo competition between PittII WT and Msf-COMP inoculated 1:1 into 6 animals compared with the previous data obtained from competition between PittII WT and Msf-KO in vivo. Each data point represents a single tissue-site CI value. Points on the X-axis (CI of 0) indicate that no KO bacteria were observed and thus have an infinitely low CI value. *p<0.05 by two-tailed t-test for two independent means of log cfu data. **p<0.05 by Mann-Whitney U test. n.s. (not significant). (E) Percentage of tissue sites that were positive for bacteria in each of the two in vivo competition experiments (WT vs Msf-KO, and WT vs Msf-COMP). * p<0.05 by two-tailed Fisher-exact test. n.s. (not significant).