Representative histology images demonstrating overall disease burden in mice infected with H37Rv, Beijing 4619, or Haarlem 923, and either sham-immunized or immunized with BCG or 422.

Mild disease burden is present mice infected with H37Rv, with minimal differences in mice immunized with either BCG or 422. Progressive pulmonary pathology developed in unprotected mice infected with clinical strains, 4619 or 923, with most severe disease occurring in mice infected with 923. Protection based on overall lesion burden is afforded by both BCG and 422 against infection with the two clinical strains. However, in mice infected with the 923 strain, more severe pathology developed in mice immunized with 422 compared to BCG.