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In vitro evaluation of Escherichia coli and Staphylococcus aureus translocation in 3D printed material
Ashma Sharma1, Joshua Prince1, A-Andrew D Jones1,2,3,4
1Department of Civil & Environmental Engineering, Pratt School of Engineering, Duke University, Durham, NC 27708.
Abstract:
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 in situ 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. De novo vascular graft materials, such as tissue-engineered vascular graft material and decellularized vasculature may provide an in situ 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 Staphylococcus aureus and Escherichia coli 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 E. coli broke through much less from tissue than from engineered materials, while S. aureus 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.
Insights
Vascular graft infections persist despite antimicrobial coatings. This study shows bacterial diffusion into synthetic grafts, not just surface contamination, is key. Future research should focus on controlling growth within the graft material.
Area of Science:
- Biomaterials Science
- Infectious Diseases
- Vascular Surgery
Background:
- Vascular graft infection is a serious complication, often occurring >30 days post-surgery.
- Antimicrobial coatings and lack of bacterial proliferation/penetration on common graft materials do not prevent infection.
- Infection may stem from suture site bacteria or slow diffusion/proliferation of systemically circulating bacteria within synthetic grafts.
Purpose of the Study:
- To investigate bacterial diffusion and breakthrough in novel vascular graft materials.
- To use confocal microscopy to quantify bacterial penetration depth and viable bacteria breakthrough over time.
- To compare diffusion and breakthrough rates of *Staphylococcus aureus* and *Escherichia coli* in alginate, GelMA, and decellularized porcine vascular tissue.
Main Methods:
- Confocal microscopy imaging of bacterial penetration depth over time.
- Quantification of viable bacteria breakthrough across different biomaterials.
- Comparative analysis of *Staphylococcus aureus* and *Escherichia coli* diffusion in alginate, GelMA, and decellularized vascular tissue.
Main Results:
- Bacterial penetration depth over time was similar across all tested biomaterials (alginate, GelMA, decellularized tissue).
- *Escherichia coli* breakthrough was significantly lower in decellularized vascular tissue compared to engineered materials.
- *Staphylococcus aureus* showed higher breakthrough rates in GelMA but similar rates in alginate and decellularized tissue.
Conclusions:
- Bacterial diffusion within the graft material, rather than surface properties alone, is critical for graft infection.
- Decellularized vascular tissue demonstrates superior resistance to bacterial breakthrough compared to engineered biomaterials.
- Controlling interstitial bacterial growth, in addition to surface modifications, is a promising strategy for engineering infection-resistant vascular grafts.
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