Assessment of the antimicrobial activity of acellular vascular grafts

Several studies have reported biological vascular grafts to be more resistant to microbial infection than synthetic counterparts in vivo. Indeed, small intestinal submucosa (SIS) materials have previously been reported to be antimicrobial. The aim of this study was to assess the antimicrobial activity and the ability to resist biofilm formation of a novel acellular vascular graft and compare it to commercially available alternatives using a range of organisms: MRSA, MSSA, Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa and Candida albicans. This was achieved using a modified disk diffusion assay and extraction of the materials into solution followed by minimum inhibitory concentration assays. To assess resistance to biofilm formation a novel biofilm assay was developed which compared the total colony forming units (CFU) recovered from each material and identification of the percentage of CFU which were loosely attached, residing within the biofilm or attached to the biomaterial. The results indicated a lack of antimicrobial activity for all materials tested, including SIS. The biological materials were more resistant to the formation of a biofilm compared to Dacron.