Staphylococcus aureus induces release of bradykinin in human plasma

Staphylococcus aureus is a prominent human pathogen. Here we report that in tact S. aureas bacteria activate the contact system in human plasma in vitr o, resulting in a massive release of the potent proinflammatory and vasoact ive peptide bradykinin. In contrast, no such effect was recorded with Strep tococcus pneumoniae. In the activation of the contact system, blood coagula tion factor XII and plasma kallikrein play central roles,and a specific inh ibitor of these serine proteinases inhibited the release of bradykinin by S . aureus in human plasma. Furthermore, fragments of the cofactor H-kininoge n of the contact system efficiently blocked bradykinin release. The results suggest that activation of the contact system at the surface of S. aureus and the subsequent release of bradykinin could contribute to the hypovolemi c hypotension seen in patients with severe S. aureus sepsis. The data also suggest that the contact system could be used as a target in the treatment of S. aureus infections.