Bacteremic Infectability of Vascular Grafts: An Experimental Study

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.