Fig 2.

Representative Gram stain images and immunohistochemical (IHC) localization of neutrophils and Staphylococcus aureus (S. aureus) from a human acellular vessel (HAV) and expanded polytetrafluoroethylene (ePTFE) explant 2 weeks after implantation in a rodent infection model. Gram-positive S.aureus (dark blue clusters) were identified within interstices of ePTFE (B) but not seen within or around HAV explant (A). Immunostaining for neutrophil elastase (green) and S.aureus (red) is shown in (C-F) and (G-J). The HAV explant had only a few intact neutrophils on the tissue and graft interface (D), but host cells (blue nuclei) infiltrated into the entire HAV wall (C and E), unlike that of the ePTFE wall (G). Numerous clusters of S.aureus were found within the ePTFE wall (G and I), but no bacteria were detected in the HAV (C). Some positive neutrophil elastase staining was observed just at the edge of the ePTFE wall, but relatively few intact nuclei were found to be associated with this staining (H). The tissue surrounding the actively contaminated ePTFE explant (J) had a high density of neutrophil elastase-positive neutrophils compared with that of the HAV implant (F). The green arrow in (C) shows autofluorescent red blood cells.