<i>In vitro</i> evaluation of <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> translocation in 3D printed material

Vascular graft infection is a rare but life threating condition, primarily occurring after 30 days post-surgery. Meta-analysis has shown that antimicrobial coatings on graft materials do not prevent these infections. Moreover, infection still occurs even though studies have also shown that there is no bacterial proliferation on or bacterial penetration of common vascular graft material. The time frame of infection, meta-analysis, and <i>in situ</i> studies suggest that bacteria present at the suture site are introduced into the surrounding tissue or that systemically circulating bacteria may be surviving, proliferating, diffusing slowly, and evading host immune defense in synthetic vascular grafts. <i>De novo</i> vascular graft materials, such as tissue-engineered vascular graft material and decellularized vasculature may provide an <i>in situ</i> platform for studying survival, proliferation, and diffusion in tissue and tissue-like materials. In this study, we use confocal microscopy to image penetration depth of bacteria over time as a proxy for diffusion of <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> into alginate, GelMA, and decellularized porcine vascular tissue. We quantified viable bacteria breakthrough as a function of biomaterial type. We found penetration depth over time was similar in all three biomaterials, however <i>E. coli</i> broke through much less from tissue than from engineered materials, while <i>S. aureus</i> had higher breakthrough in the GelMa but otherwise equal rates. These results point to the possibility of interstitial growth control relative to surface coatings as a future target for engineering infection resistance in engineered vascular grafts.