(a) Scheme for pre-colonization of EcN in the GI tract followed by P. aeruginosa infection. (b) Colonization of EcN was assessed by faecal counting of bacteria as a function of time in animals that received different numbers of cells by oral gavage. (c) The level of P. aeruginosa was tracked over 6 days after giving 1010 cfu of the pathogen to each group of pretreated mice. (d) Total viable P. aeruginosa cell counts from faecal samples at day 6 post-infection. The data from two independent experiments are shown (n=5–10). * P<0.01 (one-way ANOVA with Bonferroni correction for multiple comparisons). Data are presented in box plots with median as centre line, 10 and 90% confidence limits, and minimum and maximum values.