Staphylococcus aureusCapsular Polysaccharides

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Abstract
SUMMARY: Serotype 5 and 8 capsular polysaccharides predominate among clinical isolates ofStaphylococcus aureus.The results of experiments in animal models of infection have revealed that staphylococcal capsules are important in the pathogenesis ofS. aureusinfections. The capsule enhances staphylococcal virulence by impeding phagocytosis, resulting in bacterial persistence in the bloodstream of infected hosts.S. aureuscapsules also promote abscess formation in rats. Although the capsule has been shown to modulateS. aureusadherence to endothelial surfaces in vitro, animal studies suggest that it also promotes bacterial colonization and persistence on mucosal surfaces.S. aureuscapsular antigens are surface associated, limited in antigenic specificity, and highly conserved among clinical isolates. With the emergence of vancomycin-resistantS. aureusin the United States in 2002, new strategies are needed to combat staphylococcal infections. Purified serotype 5 and 8 capsular polysaccharides offer promise as target antigens for a vaccine to prevent staphylococcal infections, although the inclusion of other antigens is likely to be essential in the development of an effectiveS. aureusvaccine. The genetics and mechanisms of capsule biosynthesis are complex, and much work remains to enhance our understanding of capsule biosynthesis and its regulation.