Bacteremic Infectability of Vascular Grafts: An Experimental Study

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Abstract
The present study was undertaken with the aim of defining the differences, if any, in bacteremic infectability of some currently available arterial grafts. The following prostheses were investigated: • two kinds of expanded polytetrafluoroethylene (PTFE) • Dacron knitted double velour • Dacron knitted pretreated with gelatin Forty beagle dogs were used . In each animal the infrarenal aorta was resected and replaced by means of ϕ.6 mm segment of: • PTFE type I 10 dogs • PTFE type II 10 dogs • Dacron knitted double velour 10 dogs • Dacron knitted pretreated with gelatin 10 dogs At the end of the operation, each animal was administered IV with 100 mL of normal saline containing a suspension of Staphylococcus aureus coagulase-posi tive phage type 5504. The bacterial load was 105in 5 animals of each group, 107in the remaining 5. The graft was retrieved after forty-five days and studied in the microbiology laboratory (study of graft homogenate) and in the pathology laboratory (study by conventional microscopy of graft healing). When culture yielded a strain of Staph. aureus, this was retyped for phage 5504 specificity. All grafts were patent at the end of the experiment: partial thrombosis was, however, observed, coupled with a frank perigraft inflammation in: • 3 PTFE type 1 (2 Staph. 105, 1 Staph. 107) • 1 PTFE type 2 (Staph . 105) • 1 Dacron knitted double velour (Staph . 107 ) Baterial colonies within the graft tissue were evident at microscopy in 4 PTFE grafts and in 1 gelatin-pretreated graft. Culture was positive and specific in all the gelatin-treated Dacron grafts and in 60% of the nonpretreated Dacron and PTFE grafts. An optimal result (good healing, no inflammation, no infection) was observed only in 3 PTFE and in 2 "conventional" Dacron grafts. The possibility is suggested that bacteria may be harbored in graft tissue without any clinically evident effect; moreover, some late graft infection could be attributable to an early bacteremic contamination.

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