Recently we described a novel bacteriophage-encoded pathogenicity island in
Staphylococcus aureus that harbors a number of virulence factors that are all involved in the
evasion of innate immunity. Here we describe a mechanism by which staphylokinase (SAK),
frequently present on this pathogenicity island, interferes with innate immune defenses: SAK
is anti-opsonic. By activating human plasminogen (PLG) into plasmin (PL) at the bacterial
surface, it creates bacterium-bound serine protease activity that leads to degradation of two …