Staphylococcus aureus is one of the most frequently isolated bacteria from infected medical implants. S. aureus has the capacity to adhere to the surface of an implant where it forms a biofilm. We used atomic force microscopy to probe binding forces between a fibronectin-coated tip and isolates of S. aureus, which were obtained from either patients with infected prostheses or healthy humans. A unique force-signature was observed for binding events between the tip and the cells. There is a strong distinction (p=0.01) in the binding force-signature observed for S. aureus isolated from the infected vs. healthy populations. This observation suggests a fundamental correlation between nanometer scale binding forces and the clinical outcome of patients with implanted medical devices.