Do multifilament alloplastic meshes increase the infection rate? Analysis of the polymeric surface, the bacteria adherence, and the in vivo consequences in a rat model.

Within the last decade hernia surgery has changed from suture repair to mesh repair. Biomaterials, and multifilaments in particular, are thought to increase the risk of infection. Therefore, the aim of this study was to study the influence of the presence of either a monofilament or a multifilament mesh material on the bacterial infection risk. The filament surface of a monofilament and a multifilament mesh were calculated on the basis of a theoretical model. The adherence of Staphylococcus aureus was measured in vitro by fluorescence analysis. Additionally, the two mesh materials (8-mm platelets) were implanted subcutaneously in Sprague-Dawley rats with daily surveillance for clinical signs of infection. After 7 days the meshes were explanted for histological and microbiological analysis. Calculations of the mesh surface area revealed a higher level for the multifilament mesh. The extent of adherent bacteria corresponded to the estimated filament surface in vitro. In vivo, the implantation of meshes in the presence of 5 x 10(6) S. aureus did not show an increased infection rate in rats with either monofilament or multifilament material, compared to the control groups (mesh implantation without S. aureus contamination). However, after 7 days bacteria were still detectable in the majority of the implantation sites, and a clinically inapparent intensification of local inflammation and fibrosis was induced. The increased surface area of a multifilament meshes promotes the persistence of bacteria in the implant bed, though this alone is not sufficient to create a clinically apparent infection. This might explain the development of mesh-related infections after a delay of several months or even years. In vivo, the adherence of bacteria to the implant material depends on the surface area, which favors the use of monofilament materials.