Figure 6.

Rechallenge of mice previously colonised with 6B and the double mutant attenuated strains using wild type 6B and pneumonia and colonisation models. (A–C) Target organ CFU for sham-colonised, 6B colonised, or double mutant strain colonised CD1 mice challenged 30 days after colonisation by intranasal inoculation of 1 × 10⁷ CFU wild type 6B S. pneumoniae. (A) Blood, (B) lung homogenate and (C) BALF S. pneumoniae CFU (log₁₀ ml⁻¹) 24 hours following the pneumonia challenge. (D) Nasal wash CFU 7 days after intranasal recolonisation challenge of CD1 mice with 1 × 10⁷ CFU of the S. pneumoniae 6B strain 42 days after two episodes of colonisation with the wild type 6B or double mutant strains. Each symbol represents data from a single mouse, horizontal bars represent median values, error bars represent interquartile range and asterisks represent statistical significance compared to sham colonised group (Kruskall–Wallis with Dunn’s post hoc test; *, p < 0.05; **, p < 0.01).