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The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
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The cell fragments known as platelets are disc-shaped, with an average diameter of about 3 μm and a thickness of roughly 1 μm. They play a crucial role in the body's vascular clotting system, which also involves plasma proteins, blood cells, and blood vessel tissues.
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Updated: Sep 21, 2025

Analyzing Platelet Subpopulations by Multi-color Flow Cytometry
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Group B Streptococcal Hemolytic Pigment Impairs Platelet Function in a Two-Step Process.

Kristin Jahn1, Patience Shumba1, Phoenicia Quach2

  • 1Center for Functional Genomics of Microbes, Department of Molecular Genetics and Infection Biology, Interfaculty Institute for Genetics and Functional Genomics, University of Greifswald, 17489 Greifswald, Germany.

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Group B streptococci pigment activates and then kills human platelets, a key factor in severe infections. This finding reveals a novel mechanism for platelet destruction during GBS disease.

Keywords:
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Area of Science:

  • Microbiology and Immunology
  • Hematology

Background:

  • Group B streptococci (GBS) are increasingly implicated in invasive infections beyond maternal-fetal contexts, including sepsis and toxic shock syndrome.
  • These severe GBS infections are frequently associated with coagulation disorders and low platelet counts (thrombocytopenia).
  • GBS produce a pigment toxin with hemolytic, cytolytic, and coagulatory properties.

Purpose of the Study:

  • To investigate the direct impact of the GBS pigment toxin on human platelets.
  • To elucidate the mechanism by which GBS pigment affects platelet function and viability.

Main Methods:

  • Exposure of human platelets to GBS expressing the pigment toxin.
  • Assessment of platelet activation markers and cell death following GBS pigment interaction.

Main Results:

  • Infection with pigmented GBS initially triggered activation of human platelets.
  • Prolonged exposure led to necrotic cell death in the affected platelets.
  • The GBS pigment toxin was identified as the causative agent for platelet demise.

Conclusions:

  • The GBS pigment toxin plays a critical role in the pathogenesis of GBS-associated coagulopathies.
  • GBS pigment directly induces platelet activation followed by necrotic cell death, contributing to thrombocytopenia.
  • This study demonstrates that GBS pigment is a potent platelet-killing factor.