Abstract
Staphylococcus epidermidis remains the predominant pathogen in prosthetic-device infections. Ventricular assist devices, a recently developed form of therapy for end-stage congestive heart failure, have had considerable success. However, infections, most often caused by Staphylococcus epidermidis, have limited their long-term use. The transcutaneous driveline entry site acts as a potential portal of entry for bacteria, allowing development of either localized or systemic infections. A novel in vitro binding assay using explanted drivelines obtained from patients undergoing transplantation and a heterologous lactococcal system of surface protein expression were used to identify S. epidermidis surface components involved in the pathogenesis of driveline infections. Of the four components tested, SdrF, SdrG, PIA, and GehD, SdrF was identified as the primary ligand. SdrF adherence was mediated via its B domain attaching to host collagen deposited on the surface of the driveline. Antibodies directed against SdrF reduced adherence of S. epidermidis to the drivelines. SdrF was also found to adhere with high affinity to Dacron, the hydrophobic polymeric outer surface of drivelines. Solid phase binding assays showed that SdrF was also able to adhere to other hydrophobic artificial materials such as polystyrene. A murine model of infection was developed and used to test the role of SdrF during in vivo driveline infection. SdrF alone was able to mediate bacterial adherence to implanted drivelines. Anti-SdrF antibodies reduced S. epidermidis colonization of implanted drivelines. SdrF appears to play a key role in the initiation of ventricular assist device driveline infections caused by S. epidermidis. This pluripotential adherence capacity provides a potential pathway to infection with SdrF-positive commensal staphylococci first adhering to the external Dacron-coated driveline at the transcutaneous entry site, then spreading along the collagen-coated internal portion of the driveline to establish a localized infection. This capacity may also have relevance for other prosthetic device–related infections.
Highlights
Staphylococcus epidermidis is a major cause of prosthetic device infections
We examined why Staphylococcus epidermidis, a bacteria that is commonly found on the skin, is responsible for the majority of these infections
The ability of different surface molecules of S. epidermidis to attach to drivelines removed from patients undergoing transplantation was tested
Summary
Staphylococcus epidermidis is a major cause of prosthetic device infections. This capacity appears due to its ability to colonize both the skin as commensal flora and prosthetic materials via its ability to adhere to device surfaces and form biofilms [1,2,3]. Ventricular assist devices (VADs) are relatively new cardiovascular prostheses that have become a major form of therapy for patients with end-stage congestive heart failure. An important limitation to the use of VADs has been the high incidence of device-related infections, which occur in 18%–59% of patients [5,6,7,8]. These infections can affect different components of the device, such as the surgical site, the device pocket or the device itself and pose a major threat to survival since eradication usually requires device removal [5,9,10,11]
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