Hyperproduction of fibrin and inefficacy of antithrombin III and alpha2 macroglobulin in the presence of bacterial porins

Bacterial Porins and Their Procoagulant Role: Implication in the Pathophysiology of Several Thrombotic Complications during Sepsis

The association between sepsis and thrombotic complications is still not well known. Different mechanisms have been shown to be involved in the sepsis-induced prothrombotic state, but clinical scenarios may differ. In this review, we have summarized the role that bacterial products such as porins and toxins can have in the induction of the prothrombotic state during sepsis and the interaction that they can have with each other. Furthermore, the above-mentioned mechanisms might be involved in the pattern of the clinical presentation of thrombotic events during bacterial sepsis, which would secondarily explain the association between sepsis and venous thromboembolism, the association between sepsis and disseminated intravascular coagulation, and the association between sepsis and microangiopathic venous thromboembolism.

Resolution of Disseminated Intravascular Coagulation in a Patient with COVID-19 and Associated Sepsis-Induced Neutropenia

COVID-19 has been associated with a hypercoagulable state and thrombotic events. Venous thromboembolism has been the most commonly reported type of thrombosis but also arterial thrombosis and disseminated intravascular coagulation in inpatients have been described frequently in several clinical experiences. Patients with COVID-19, because of its tendency to induce leucopenia and overlapping of bacterial infection, may experience sudden disseminated intravascular coagulation (DIC), as in the case that we report here. However, early diagnosis and treatment may be associated with positive resolution of these severe complications.

Bacterial pathogens activate plasminogen to breach tissue barriers and escape from innate immunity

Both coagulation and fibrinolysis are tightly connected with the innate immune system. Infection and inflammation cause profound alterations in the otherwise well-controlled balance between coagulation and fibrinolysis. Many pathogenic bacteria directly exploit the host's hemostatic system to increase their virulence. Here, we review the capacity of bacteria to activate plasminogen. The resulting proteolytic activity allows them to breach tissue barriers and evade innate immune defense, thus promoting bacterial spreading. Yersinia pestis, streptococci of group A, C and G and Staphylococcus aureus produce a specific bacterial plasminogen activator. Moreover, surface plasminogen receptors play an established role in pneumococcal, borrelial and group B streptococcal infections. This review summarizes the mechanisms of bacterial activation of host plasminogen and the role of the fibrinolytic system in infections caused by these pathogens.

Clinical review: molecular mechanisms underlying the role of antithrombin in sepsis

In disseminated intravascular coagulation (DIC) there is extensive crosstalk between activation of inflammation and coagulation. Endogenous anticoagulatory pathways are downregulated by inflammation, thus decreasing the natural anti-inflammatory mechanisms that these pathways possess. Supportive strategies aimed at inhibiting activation of coagulation and inflammation may theoretically be justified and have been found to be beneficial in experimental and initial clinical studies. This review assembles the available experimental and clinical data on biological mechanisms of antithrombin in inflammatory coagulation activation. Preclinical research has demonstrated partial interference of heparin – administered even at low doses – with the therapeutic effects of antithrombin, and has confirmed – at the level of cellular mechanisms – a regulatory role for antithrombin in DIC. Against this biological background, re-analyses of data from randomized controlled trials of antithrombin in sepsis suggest that antithrombin has the potential to be developed further as a therapeutic agent in the treatment of DIC. Even though there is a lack of studies employing satisfactory methodology, the results of investigations conducted thus far into the mechanisms of action of antithrombin allow one to infer that there is biological plausibility in the value of this agent. Final assessment of the drug's effectiveness, however, must await the availability of positive, prospective, randomized and placebo-controlled studies.