Vascular prosthetic infection with Staphylococcus epidermidis: experimental study of pathogenesis and therapy

To determine whether a slime-producing strain of Staphylococcus epidermidis was capable of producing acute infection of a prosthetic vascular graft, 5 cm segments of knitted Dacron were implanted in the infrarenal aortic position of dogs in three groups of animals. These included a control group (no graft contamination), a contaminated group that received a graft soaked in an S. epidermidis solution (untreated group), and a contaminated group in which perioperative antibiotics (three doses of cefamandole, 100 mg/kg) were administered (prophylaxis group). In all the animals reexploration and graft removal were performed at 10 days, with replacement of the defect being achieved with a new uncontaminated graft. These animals underwent exploration a third time after an additional 10-day period. S. epidermidis was not grown from the control animals (n = 7) but was cultured in 44% of the prophylaxis group (n = 9) and 88% of the untreated group (n = 16) during at least one of the operative procedures (chi 2 = 15.859; p less than 0.001). The pathologic features of acute S. epidermidis infection were best seen in the untreated animals and included anastomotic disruption (56%), periaortic hematoma, and lymphadenopathy (94%). Microscopic examination of the aortic tissues revealed extensive infiltrates of leukocytes, macrophages, and foreign body giant cells with aortic necrosis. These features were less prominent in the prophylaxis animals. We conclude that S. epidermidis is capable of producing acute graft infection with perigraft inflammation and anastomotic disruption. The administration of perioperative antibiotics reduced but did not abolish these effects of bacterial contamination of prosthetic vascular grafts.