Adherence ofStaphylococcus aureusto Endothelial Cells: Influence of Capsular Polysaccharide, Global Regulatoragr, and Bacterial Growth Phase

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Abstract
The adherence ofStaphylococcus aureusto human endothelial cells (EC) is probably an important step in the pathogenesis of systemic staphylococcal infections. We examined the influence of type 5 capsular polysaccharide (CP5) production, the global regulatoragr, and the bacterial growth phase onS. aureusadherence to EC. WhereasS. aureusNewman showed maximal adherence to EC in the logarithmic phase of growth, an isogenicagrmutant showed maximal adherence in the stationary growth phase.S. aureusadherence to EC and CP5 expression were negatively correlated: a mutation in theagrlocus diminished CP5 production and led to increased adherence. Likewise, induction of CP5 expression by addition of NaCl to the growth medium resulted in reduced staphylococcal adherence to EC.S. aureusNewman cells that adhered to EC did not express CP5. A Newmancap5Omutant was acapsular and showed significantly greater adherence to EC than the parental strain did (P< 0.005). Complementation of thecap5Omutation intransrestored CP5 expression and reduced EC adherence to a level similar to that of the parental strain. The enhanced adherence shown by thecap5Omutant was similar in magnitude to that of theagrmutant or thecap5O agrdouble mutant. Cells of thecap5Omutant andcap5O agrdouble mutant harvested from stationary-phase cultures adhered significantly better than did cells harvested in the exponential growth phase. These data are consistent with the postexponential andagr-independent expression byS. aureusof at least one putative EC adhesin, whose binding domain may be masked by CP5.

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