Staphylococcus aureusadheres avidly to decellularised cardiac homograft tissue in vitro in the fibrinogen-dependent manner

Abstract

Objective: Infective endocarditis remains a severe complication associated with a high morbidity and mortality in patients after heart valve replacement. Exploration of the pathogenesis is of high demand and we, therefore, present a competent model that allows studying bacterial adherence and the role of plasma fibrinogen in this process using a new in-house designed low-volume flow chamber. Three cardiac graft tissues used for pulmonary valve replacement have been tested under shear conditions to investigate the impact of surface composition on the adhesion events. Methods: Tissue pieces of cryopreserved homograft (non-decellularised), decellularised homograft and bovine pericardium patch were investigated for fibrinogen binding. Adherence of Staphylococcus aureus to these graft tissues was studied quantitatively under flow conditions in our newly fabricated chamber based on a parallel plates’ modality. The method of counting colony-forming units was reliable and reproducible to assess the propensity of different graft materials for bacterial attachment under shear. Results: Bacterial perfusions over all plasma-precoated tissues identified cryopreserved homograft with the lowest affinity for S. aureus compared to decellularised homograft presenting a significantly higher bacterial adhesion (p < 0.05), which was linked to a more avid fibrinogen binding (p < 0.01). Bovine pericardial patch, as a reference tissue in this study, was confirmed to be the most susceptible tissue graft for the bacterial adhesion, which was in line with our previous work. Conclusion: The two studied homograft tissues showed different levels of bacterial attachment, which might be postulated by the involvement of fibrinogen in the adhesion mechanism(s) shown previously for bovine tissues.

An In Vitro Model to Study Endothelialization of Cardiac Graft Tissues Under Flow

“…(B) In vitro small volume parallel-plate flow chamber system of dimensions LxWxH: 88 mm x 38 mm x 10.5 mm, (in-house design) based on a previously developed system. 28 All elements (I-IV) were positioned in the metal frame (V) on which a plastic microscopic slide was placed as first (I).…”

“…This flow chamber of dimensions LxWxH: 88 mm x 38 mm x 10.5 mm was designed for perfusing different media over small circular tissue pieces. 28 A plastic microscopic slide (Fig. 1B, I) was first positioned on the bottom of the metal frame.…”