The intercellular adhesin locus ica is present in clinical isolates of Staphylococcus aureus from bacteremic patients with infected and uninfected prosthetic joints

Although polysaccharide intercellular adhesin (PIA) is thought to be crucia l in the pathogenesis of prosthetic device infections caused by Staphylococ cus epidermidis, its role in prosthetic device infections caused by Staphyl ococcus aureus is unknown. To assess the clinical impact of PIA production, isolates from 15 prospectively identified cases of S. aureus bacteremia in patients with prosthetic joints (8 infected, 7 uninfected) were characteri zed for biofilm production, hemagglutination, and the presence of a 419-bp amplification product within icaA. Although icaA was present in ail 15 isol ates, none of the isolates produced hemagglutination and only one isolate ( from a patient with an uninfected prosthetic device) weakly produced biofil m in vitro. These results support the observation that the ica locus is con served between S. epidermidis and S. aureus and that PIA may be expressed o nly under in vivo conditions. Future investigations should include animal m odels to approximate the complex milieu surrounding implanted prosthetic me dical devices.