Species Differences in the Infectability of Vascular Grafts

The susceptibility of different species to bacteremia may influence the results of studies on vascular graft infection. The present study compares prosthetic graft infection in canine and porcine models. Thirty-four mongrel dogs and 38 Yorkshire pigs underwent replacement of the infrarenal aorta with a 3-cm segment of a woven Dacron prosthesis. At the lime of closure, each animal received an intravenous inoculum of 102 to 108 Staphylococcus aureus (S. aureus) Graft cultures at 1 week produced a predictable infection rate in dogs, while pigs developed only random infections (dogs: 23/34; pigs: 7/38: p = 0001). The median infective dose (ID50) in dogs was 102.9 but pigs did not develop enough infections to determine this value. Electron microscopy revealed a smooth fibrin surface in grafts explanted from pigs, while grafts from dogs demonstrated bacteria enmeshed in an irregular fibrinous lining. Prosthetic vascular grafts in dogs are more susceptible to hematogenous infection than those in pigs. Because he...