PmrA(D51A) is important for intramacrophage replication and mouse virulence. (A) PmrA D51 is required for replication within PMA-induced (10 ng/ml) THP-1 cells at a multiplicity of infection of 50:1. Closed circles, F. novicida wild type; open circles, F. novicida ΔpmrA mutant; open squares, F. novicida ΔpmrA pKK214pgroEL [pmrA]; closed squares, F. novicida ΔpmrA pKK214pgroEL [pmrA D51A]; closed triangles, F. novicida ΔkdpD strain. (B) PmrA D51 is required for maximal virulence of F. novicida in mice. Bacteria were given intranasally to groups of five anesthetized female 6- to 8-week-old BALB/c mice at a dose of 1 × 103 or 1 × 106 CFU. Closed circles, 1 × 103 F. novicida ΔpmrA pKK214pgroEL [pmrA]; closed squares with solid line, 1 × 103 F. novicida ΔpmrA pKK214pgroEL [pmrA D51A]; closed squares with dashed line, 1 × 106 F. novicida ΔpmrA pKK214pgroEL [pmrA D51A].