Fig. S3.

C57BL/6 mice were infected via tail vein injection with 1 × 10⁷ cfu of USA300 WT, fakA-, or essB-mutant strains. (Upper Left) After 8 d, the mice were killed, and bacterial survival in one kidney from each surviving mouse was enumerated. (Upper Right) The remaining kidney was formalin fixed, processed by routine methods, and H&E stained. Histologic sections were manually scored for pyelonephritis severity on a four-point scale based on the microscopically estimated fraction of tissue involved by inflammation and/or necrosis: 1, <1% involvement; 2, 1–5% involvement; 3, 5–25% involvement; 4, >25% involvement. (Lower) Gram staining (images) confirms renal Gram-positive bacterial microabscesses associated with features of microfilm (amorphous matrix and branching channels), regardless of genotype.