Phagocytosis and oxidative-burst response of planktonic Staphylococcus epidermidis RP62A and its non-slime-producing variant in human neutrophils.

The ability of bacterial organisms to produce an extracellular polysaccharide matrix known as slime has been associated with increased virulence and delayed infections in various prosthetic implants. Within a biofilm, this slime may protect the embedded bacteria from host defense mechanisms, especially phagocytosis by polymorphonuclear leukocytes. To determine whether planktonic Staphylococcus epidermidis is protected in a similar way, a novel flow cytometric assay was performed, measuring ingestion and adherence during phagocytosis and the production of superoxide during oxidative burst. Hydrophobicity was determined by hydrophobic interaction chromatography. Slime-producing S. epidermidis RP62A and its phenotypic variant, non-slime-producing RP62A-NA, were compared. The results showed increased phagocytosis of RP62A at 2, 5, 10, and 30 min; increased adherence of RP62A at 30 s and 30 min; and increased superoxide production of RP62A after 2 min. Decreased hydrophobicity of RP62A over RP62A-NA was correlated with a hydrophilic slime coat. The data argue that the host aggressively combats slime-producing S. epidermidis. This biological phenomenon is potentially important during bacteremia to prevent further adhesion, accumulation, and the genesis of a bacterial biofilm on implants or tissue surfaces.