Histologic and Biomechanical Evaluation of Biologic Meshes following Colonization with Pseudomonas aeruginosa

BackgroundBiologic meshes have become increasingly popular for the repair of abdominal wall defects, especially in contaminated sites. The purpose of this study was to evaluate the histologic and biomechanical properties of biologic mesh in response to a bacterial encounter.Material and MethodsA rat model of Pseudomonas aeruginosa colonization and infection of subcutaneously implanted biologic mesh was used. Samples of biologic meshes [acellular human dermis (ADM) and porcine small intestine submucosa (SIS)] were inoculated with P. aeruginosa (105 or 109 cfu) or saline as a control prior to wound closure (n = 6 per group). After 10 or 20 d, the meshes were harvested. The recovered meshes were analyzed for histologic changes and bacterial recovery as well as the material strength properties. Statistical significance (P < 0.05) was determined using 1-way analysis of variance or Mann-Whitney test.ResultsADM and SIS colonized with 109 cfu P. aeruginosa showed an increased inflammatory response with an associated decrease in neo-vascularization (P < 0.05) at 20 d post-implantation compared with controls. P. aeruginosa had no effect on the tensile strength of ADM, but the tensile strength and modulus of elasticity were reduced for SIS compared with controls at 20 d.ConclusionBacterial colonization of ADM and SIS with 109cfu P. aeruginosa negatively effected neovascularization and cellular re-population of the material over time but only SIS showed alterations in their biomechanical properties in response to this gram-negative bacterial challenge.