Bacterial load in the lungs of infected mice (n=10) were measured post sacrifice. Data represent mean ± s.e.m. * denotes P < 0.05, ** denotes P < 0.01 and **** denotes P <0.0001 by one-way ANOVA with Bonferroni's post hoc test for multiple comparisons. n.s. denotes not significant. Exact P values are shown in Appendix Table S4. 