Intravegetation antimicrobial distribution in endocarditis: a numerical model and establishment of the conditions for an in-vitro test.

Two problems appear when it is desired to get good knowledge concerning transfer of matter through a material, and especially the penetration of antibiotics into vegetations on heart valves. One is to build a numerical model to describe and simulate the process and thus to gain a fuller insight into the nature of the transfer. The other is to develop an in vitro test to represent the in vivo process, with simple operational conditions and accurate measurements. The in vitro test must enable one to measure the parameters of interest, i.e. the diffusivity of antibiotic through the vegetation, or rather through the blood located in the vegetation. Experiments and calculations are made in order to build a numerical model describing the process and to develop an in vitro test capable of determining the diffusivity. A simulation is made with a polymer bead made of Ethylene vinyl acetate saturated by a liquid such as n-heptane with a slight amount of benzene. The release of benzene from the polymer bead into n-heptane free from benzene is the best way for measuring the diffusivity of the benzene (simulating the antibiotic) through the liquid located in the polymer.