Figure 5.

Characterization of the speA⁺ M1T1 strains 5636 and 5636ΔspeA-comp (solid symbols and bars) and the isogenic speA⁻ knockout mutant 5636ΔspeA (open symbols and bars). A) SpeB activity in cell-free stationary phase supernatants (mean±se). B) Percentage survival during coculture with human neutrophils in vitro (mean±se). C) Relative adherence to the human epithelial HEp-2 cell line in vitro (mean±se). D) Capacity to switch to an invasive SpeB⁻ phenotype at the site of local infection was determined during a 3-d subcutaneous passage in C57BL/J6 mice. Each data point represents the percentage of SpeB⁻ cfu recovered from a single mouse (n=10/strain). E) Relative virulence of 5636 (9.0×10⁶ cfu/dose), 5636ΔspeA (1.4×10⁷ cfu/dose), and 5636ΔspeA-comp (1.4×10⁷ cfu/dose) was assessed over a 10-d period following subcutaneous infection of humanized plasminogen transgenic AlbPLG1 mice (n=10 mice/strain).