Ulcer bed infection. Report of a case of enlarging venous leg ulcer colonized by Pseudomonas aeruginosa

We report a case of ulcer bed infection in an enlarging venous leg ulcer without clinical signs of cellulitis in the surrounding tissues. Signs of infection in the leg ulcer were: 1) cocci-like structures and bacteria-like rods around vessel walls in the viable ulcer bed, 2) vasculitis-like inflammation of deeply situated vessels of the viable tissue, 3) Pseudomonas aeruginosa-specific antibodies in the serum (other than against exotoxin A), 4) extensive epidermolysis of normal human skin by the wound exudate in vitro, and 5) P. aeruginosa exotoxin A in the wound exudate (23 ng/ml). In an in vitro cell assay, the wound exudate was cytotoxic and rabbit antibodies to exotoxin A, but not a serine proteinase inhibitor, inhibited this cytotoxicity. P. aeruginosa exotoxin A might contribute to the pathogenesis of the ulcer enlargement. The ulcer improved after the third skin graft, probably mainly due to effective treatment with a long-stretch compression bandage.