A. Analysis of Fn colonization in mouse xenograft tumors by IHC. An inoculum of 5×106 HCT116 cells was injected subcutaneously and bilaterally into the nude mice. Once the tumors became visible (after 3-4 days), approximately 5×106 CFU of Fn 12230 washed in PBS or 1 mg/ml Congo Red (CR) were injected into the tumors. The tumors were extracted one week later, and the formalin-fixed and embedded (FFPE) tissues were stained with mAb 7H7. Note the brown stains in tumor injected with PBS-washed tumor, but not in CR-washed tumor. Scale bar = 20 μM. 