The effect of apo-transferrin on bacterial adhesion to biomaterials

Apo-transferrin (apo-Tf), the iron deficient form of Tf, has been identified previously as a potent inhibitor of Staphylococcus epidermidis adhesion to polyurethane surfaces. In this study, the ability of apo-Tf to suppress the adhesion of two other strains of bacteria, namely a Gram-positive Staphylococcus aureus and a Gram-negative Pseudomonas aeruginosa to several biomaterials, including polystyrene, polymethylmethacrylate, and silicone, is documented. The presence of apo-Tf in the medium at 20 microg/ml lowered bacterial adhesion to all tested biomaterials more than fourfold. Moreover, apo-Tf exerted its inhibitory activity even when protein coated surfaces were used as substrates for bacterial adhesion. To emphasize the importance of apo-Tf in the prevention of bacterial adhesion, human serum was depleted of Tf, employing affinity chromatography, and was shown to lose its inhibitory activity toward bacterial adhesion. Upon addition of apo-Tf to Tf-depleted serum, the activity was reestablished, resulting in a marked reduction in the number of bacteria adhered to the surfaces. Following the enzymatic deglycosylation, apo-Tf retained its ability to prevent bacterial adhesion. These results indicate that the carbohydrate moiety does not seem to play a role in this activity. The presented data provide the evidence that the inhibitory activity of apo-Tf is not bacterial strain specific and that the presence of apo-Tf in the medium results in a significant reduction of bacterial adhesion to a variety of neat and/or protein coated surfaces.