Surface Proteins of Staphylococcus epidermidis

Abstract

Staphylococcus epidermidis is a ubiquitous commensal of human skin. The widespread use of indwelling medical devices in modern medicine provides an opportunity for it to cause infections. Disease causing isolates can come from many different genetic backgrounds. Multiply antibiotic resistant strains have spread globally. S. epidermidis has a smaller repertoire of cell wall anchored (CWA) surface proteins than Staphylococcus aureus. Nevertheless, these CWA proteins promote adhesion to components of the extracellular matrix including collagen, fibrinogen, and fibronectin and contribute to the formation of biofilm. The A domain of the accumulation associated protein Aap can promote adhesion to unconditioned biomaterial but must be removed proteolytically to allow accumulation to proceed by homophilic Zn 2+-dependent interactions. Mature biofilm contains amyloid structures formed by Aap and the small basic protein (Sbp). The latter contributes to the integrity of both protein and polysaccharide biofilm matrices. Several other CWA proteins can also promote S. epidermidis biofilm formation.

Virulence Factors in Coagulase-Negative Staphylococci

“…Surface-associated adhesins have an important role in biofilm formation, both in the initial adhesion to host proteins and tissues, and biofilm maturation. These adhesins comprise covalently and non-covalently anchored proteins, as well as non-proteinaceous factors (reviewed in [35][36][37][38]). Covalently anchored proteins, or also called cell wall-anchored (CWA) proteins, are characterized by the presence of the LPXTG motif, which is recognized by the sortase enzyme that, in turn, conducts the process of anchoring the protein to the peptidoglycan [39].…”

“…Within the group of the non-covalently anchored cell wall are the autolysins/adhesins AtlE and Aae. Lastly, the non-proteinaceous group is composed of teichoic acids (TAs) and the polysaccharide intercellular adhesion (PIA) [35][36][37][38]. The function of these molecules will be briefly discussed in this section in the context of their contribution to biofilm formation.…”

“…Thus, it was hypothesized that molecules other than PIA were implicated in biofilm maturation. We thus learned that biofilm formation can be supported or completely mediated by proteins [34][35][36]. In fact, S. lugdunensis biofilms are mostly composed of proteins rather than PNAG [90,93].…”

“…Biofilm accumulation by Aap is determined by Domain-B that becomes active only upon cleavage of the native protein [95,96]. Accordingly, the matrix of S. epidermidis biofilms is composed of a mixture of fully and partially cleaved proteins [35]. Recently, it was shown that the bacterial metalloprotease SepA is able to cleave the Domain-A of Aap resulting in enhanced biofilm accumulation in S. epidermidis [97].…”

Monoclonal Antibodies Targeting Surface-Exposed and Secreted Proteins from Staphylococci

“…Of the almost 50 species of staphylococci identified so far, most are coagulase-negative, like Staphylococcus epidermidis , while a few, such as Staphylococcus aureus , are coagulase-positive. S. epidermidis is a colonizer of the human skin and nares and plays an important role in the maintenance of healthy skin flora [ 1 , 2 ]. S. epidermidis is also recognized as an opportunistic pathogen that can cause important problems, especially during biofilm formation on the surface of indwelling medical devices [ 3 ].…”