Competitive survival of (A) LACΔpsmα, (B) LACΔspa, (C) 502AΔagrA and (D) 1695ΔagrA in the lungs at 5 h after infection of C57BL/6 mice in a 1:1 mixture with the corresponding parent strains (A-C), 1695 or LAC-JE2 (D). Each symbol represents the fold change of CFU. **P< 0.01, ***P< 0.001, t test. Data shown were combined from two independent experiments.