Quantitative Bacterial Analysis of Porous, Fabric, and Smooth Non-Blood Contacting Implant Surfaces and Their Tissue Interfaces in a 169 Day Pneumatic Total Artificial Heart Animal Recipient

Abstract

All long-term total artificial heart (TAH) survivals are subject to sepsis. Survival can be prolonged, but the source of the infection cannot be eliminated with any known course of antibiotics or treatment regimen. Sambo, a U-100 pTAH calf, survived 169 days. At week 6, he became septic, growing a Pseudomonas species (Ps). Weekly blood cultures were intermittently positive until week 13 when they became continuously positive until his demise, from a ruptured left ventricular pumping diaphragm. Spatially specific porous silicone rubber (SSP) was used for surface modifications on the drive lines and as cuffs around the Dacron TAH graft to large vessel anastomoses. This gave an excellent opportunity to examine two types of porous implants surfaces (Dacron grafts and SSP) to the smooth Biomer ventricular surfaces with their respective adjoining tissue interfaces for bacterial colonization. Nine tissue samples and 13 implant surfaces were processed with Costerton's quantitative bacterial techniques. The largest numbers of bacteria (> 10(6)/cm2 Ps.) were grown from the smooth ventricular surface and in the cul-de-sac where the SSP delaminated from the driveline (two smooth implant surfaces in contact but without tissue apposition). The Dacron grafts were intermediate in bacterial concentrations and SSP surface modified drivelines and tissues were sterile. In this model, the more intimate biointegration found in the porous implants showed improved bacterial resistance in a chronically infected pTAH. The more completely biointegrated and neo-vascularized porosity SSP was the only implant surface and opposing implant tissue interface sampled to remain sterile.