Microbial Factors None of the major virulence factors or toxins of S aureus have been found in CoNS, and it seems clear that the development and persistence of CoNS infections, which are so often associated with foreign materials, are due to different mech- anisms, such as adherence. The initial nonspecific attachment by means of physicochemical forces is followed or accom- panied simultaneously by the specific interaction of bacterial surface adhesins with the uncoated device directly and with host proteins that coat the device. CoNS may adhere directly to plastic polymers on the surface of the device via fimbria- like surface protein structures53 or via a capsular polysaccha- ride (polysaccharide/adhesin). Antibodies to polysaccharide/ adhesin (either produced actively by immunization or infused passively as polyclonal or monoclonal antibodies) prevent experimental S epidermidis catheter infections54 and experi- mental endocarditis55 in animals. Bacteria may also adhere to host matrix proteins that coat the surface of an implanted device.56 Host extracellular matrix proteins include fibrinogen, fibronectin, and collagen that are deposited on newly implanted biomaterials.57,58 Staphylococci have a variety of surface adhesins, some known collectively by the acronym MSCRAMM (microbial surface components reacting with adherence matrix mole- cules), that allow the pathogen to establish a focus of Biofilm Formation Subsequent accumulation of bacteria on top of bacteria that adhere to a device surface requires the production of so-called polysaccharide intercellular adhesin, which is strongly asso- ciated with the staphylococcal cell surface and mediates cell-to-cell adhesion.50,59 The layers of bacteria on the surface of an implanted device are encased in this extracellular slime60 and constitute a biofilm. Biofilm is defined as a surface-associated community of 1 or more microbial species that are firmly attached to each other and the solid surface and are encased in an extracellular polymeric matrix that holds the biofilm together. 