Atomic force microscopy was used to "fish" for binding reactions between a fibronectin-coated probe (i.e., substrate simulating an implant device) and each of 15 different isolates of Staphylococcus aureus obtained from either patients with an infected cardiac prosthesis (invasive group) or healthy human subjects (control group). There is a strong distinction (p = 0.01) in the binding-force signature observed for the invasive versus control populations. This observation suggests that a microorganism's "force taxonomy" may provide a fundamental and practical indicator of the pathogen-related risk that infections pose to patients with implanted medical devices.