Immobilized phage proteins for specific detection of staphylococci

Rapid, specific detection of pathogenic bacteria remains a major challenge in infectious disease diagnostics. Bacteriophages can show genus- or even species-level specificity and have been developed for biosensing purposes, but the possibility of using individual phage proteins for detection has not been fully explored. This work exploits the ability of specific phage proteins, the endolysins LysK and Φ11, and the bacteriocin lysostaphin, fixed on silicon wafers to bind staphylococci. The proteins show activity against eight tested clinical isolates of S. aureus and to S. epidermidis, but no binding to Escherichia coli and limited binding to Micrococcus. Binding was quantified by clearing assays in solution and by functionalization of silicon wafers followed by light microscopy. Bacterial binding densities on functionalized surfaces were ~3 cells/100 μm(2). The small size of the proteins makes the system robust and easy to handle, and the principle is generalizable to many different biosensor platforms, including label-free systems such as optical microresonators.