Detection of bacterial adherence on biomedical polymers

The ability to adhere to materials and promote formation of a biofilm is an important feature of the pathogenicity of some organisms, most notably the coagulase negative staphylococci. Various methods to detect bacterial adherence are available, but detection of adherence to nontransparent materials can be difficult. It was the purpose of this study to establish the suitability of a dye elution technique to detect adherence. The technique involves fixing the bacterial film with formalin, staining with crystal violet, eluting the dye with ethanol, and determining the optical density of the solution using 96-well plates and an enzyme immunosorbent assay reader with a 540-nm filter. This technique distinguished a known adherent from a known nonadherent organism and demonstrated that the presence of protein can inhibit adherence, and that adherence of different organisms to different biomedically important polymers can be measured. The dye elution technique was used to evaluate the adherence of known slime-producing polysaccharide antigen-positive (PSA+) and known nonslime-producing polysaccharide antigen-negative (PSA-) Staphylococcus epidermidis organisms to implant grade materials (polyethylene, expanded polytetrafluoroethylene, Dacron, silicone, and collagen) as well as to polystyrene.