In-vivo bacterial adherence to intracardiac prosthetic materials: a new experimental model

Bacterial colonization of inert artificial materials is a critical variable in the appearance of foreign body-centered infections. Hence, a new experimental endocarditis model was evaluated that enables quantitative in-vivo testing of bacterial adherence to prosthetic materials.

In 53 rabbits, different patches of either Dacron (DAC; n = 16), glutaraldehyde-fixed pericardium (GAP; n = 18) or cryopreserved allograft (AG; n = 19) were threaded onto a Prolene suture and led through a stitch incision at the left atrium to the ventricle, perforating the mitral valve and leaving the heart at the outside of the left ventricle. The patch became caught in the valve tissue, creating mitral insufficiency. At 6 h after surgery, 6 x 10(6) colony-forming units (CFU) of Staphylococcus aureus were administered intravenously. Postmortem examination and further analysis were carried out 48 h after bacterial inoculation.

Ten animals (two DAC, four GAP, four AG) died and were excluded. Subsequently, sterile patches were found in 6/14 animals of the DAC group, in 9/14 of the GAP group, and in 9/15 of the AG group. The mean numbers of cultured organisms in the remaining patches were 2.3 x 10(6) + 7.6 x 10(6)/mg (DAC), 1.8 x 10(4)+/-6.7 x 10(4)/mg (GAP) and 4.9 x 10(5)+/-1.0 x 10(6) CFU/mg (AG). Differences in the number of CFU were not significant for all groups.

The above-described model allows reliable quantitative in-vivo testing of bacterial adherence to different prosthetic materials within a short time period. The results suggest that, with regard to avoiding the development of bacterial endocarditis, biomaterials have no advantage over Dacron.