Platelets promote bacterial dissemination in a mouse model of streptococcal sepsis.

Platelets have been reported to contribute to inflammation and inflammatory disorders. In the present study, we demonstrate that platelets contribute to the acute response to bacterial infection in a mouse model of invasive Streptococcus pyogenes infection. Thrombocytopenia occurred rapidly in infected animals and this was associated with platelet activation, formation of platelet-neutrophil complexes and neutrophil activation. In order to assess the role of platelets during infection, platelets were depleted prior to infection. Platelet-depleted animals had significantly decreased platelet-neutrophil complex formation and neutrophil activation in response to infection. Importantly, significantly fewer bacteria disseminated to the blood, lungs, and spleen of platelet-depleted animals. Platelet-depleted animals did not decrease as significantly in weight as the infected control animals. The results demonstrate a previously unappreciated role for platelets during the pathophysiological response to infection, whereby S. pyogenes bacteria bind to platelets and platelets facilitate bacterial dissemination.