Staphylococcus epidermidis in biomaterial-associated infections

Coagulase-negative staphylococci, mainly Staphylococcus epidermidis, are currently the most frequent cause of hospital acquired infections in the USA. Mostly, but not exclusively, S. epidermidis infections are linked to the use of implanted medical devices like central venous catheters, prosthetic joints and heart valves, pacemakers, cardiac assist devices, cerebrospinal fluid shunts, and intraocular lenses. As new molecular techniques reveal that S. epidermidis are by no means the most prominent bacteria of the skin and mucous membrane flora, the implication is that S. epidermidis has specific virulence factors, which transforms this commensal bacterial species into one of the most successful pathogens in modern medicine. A vast array of specific attachment factors for native and host protein-modified device surfaces and the ability to accumulate in adherent multilayered biofilms appear to be vital for the success of S. epidermidis as a pathogen. Biofilm formation contributes to the ability of the organism to withstand the host's innate and acquired immune defense mechanisms and to resist antimicrobial therapy, so that device removal is a regular feature for the treatment of S. epidermidis biomaterial-associated infection. Recent developments in the understanding of S. epidermidis virulence are reviewed in this chapter.