Experimenters or Amateurs?

A Narrative Review of Experimental Assessment to Study Vascular Biomaterials Infections and Infectability

Objective

Many experimental studies have been conducted to evaluate vascular and endovascular graft infections (VGEIs) and infectability in order to elaborate strategies to prevent or to treat their occurrence. A systematic literature search was conducted to collect and summarise key features of infection and infectability assessment techniques in VGEI experimental models.

Methods

The literature search was conducted using the Medline and Cochrane databases, with no limit on the date of publication, until 10 August 2021. Ex vivo, in vitro, and in vivo animal studies on VGEIs, published in English or French, were selected. Cross references retrieved from selected articles on PubMed database were also included in the search. Data were collected on the techniques and the protocols performed for vascular graft infection and infectability assessment.

Results

A total of 243 studies were included in the review: 55 in vitro studies, 169 animal studies, 17 combining the two models, and two ex vivo studies. Many experimental techniques were performed, with a lot of protocol discrepancies. The main experiments conducted were bacterial culture, with (n = 82 studies) or without sonication (n = 120), histopathology (n = 69), scanning electron microscopy (n = 36), and graft diffusion tests (n = 28). These techniques were used to answer different research questions corresponding to different graft infection steps, such as microbial adhesion and/or viability, biofilm biomass or organisation, human cell reaction, or antimicrobial activity.

Conclusion

Many experimental tools are available to study VGEIs, but to improve their reproducibility and scientific reliability research protocols must be standardised and include sonication of grafts before microbiological culture. Moreover, the key role of the biofilm in VGEI physiopathology must be taken into account in future studies.

A Narrative Review of Experimental Models to Study Vascular Grafts Infections

Background

Many experimental models have been developed to decipher the mechanisms of vascular graft and endograft infections (VGEIs), and to elaborate strategies to prevent or treat their occurrence. A systematic literature research was conducted to identify the most accurate models for studying VGEIs, depending on the research question.

Methods

A narrative literature search was conducted using the MEDLINE and Cochrane databases, with no set limit on the date of publication, up to 10 August 2021. Ex vivo, in vitro, and in vivo animal studies on VGEIs, published in English or French, were selected. Cross references retrieved from selected articles on PubMed database were also included. Data on microorganisms and grafts studied, details of experimental models, and of graft implantation and removal in animal studies were collected.

Results

A total of 243 studies were included in the review after reading the full length articles: 55 in vitro studies, 169 animal studies, 17 studies which used both in vitro and animal models, and two ex vivo studies. Many differences in model characteristics were seen. The main in vitro model was the incubation of a graft sample in a bacterial solution, used to study the first steps of infection. In animals, vascular large animal models (dogs and pigs) were the most commonly described but supplanted over time by extravascular and particularly subcutaneous mouse and rat models, which have been reported increasingly over the last few years. In animal models, antibiotic prophylaxis and therapy were rarely administered (27.4% and 19.9%, respectively), and vascular reconstruction after VGEIs even less frequently (9.8%).

Conclusion

Despite protocol discrepancies, it was possible to dinstinguish three main experimental models (i.e., in vitro and in vivo vascular models, and extravascular models), which all remain of interest to study specific phases of VGEIs.

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Experimental models of vascular (endo)graft infections (VGEIs) can be split into in vitro, extravascular, and vascular ones.

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Each of these three groups can help answer specific questions on VGEIs.

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To improve reproducibility, future experimental studies require standardisation.

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Experimental studies should reproduce real life conditions as accurately as possible.