fibrin and Klebsiella-Infections

Topics: Animals; Blood Coagulation; Caspases, Initiator; Cell Death; Cytokines; Fibrin; Host-Pathogen Interactions; Inflammation Mediators; Klebsiella Infections; Klebsiella pneumoniae; Lung; Mice, Inbred C57BL; Neutrophils; Pneumonia

Essentials Immunity and coagulation are linked during sepsis but the role of thrombin is not fully elucidated. We investigated the effect of thrombin inhibition on murine Klebsiella pneumosepsis outcome. Thrombin is crucial for survival and limiting bacterial growth in pneumonia derived sepsis. Thrombin improves host defense via fibrin and enhancement of platelet-neutrophil interactions.. Background Innate immunity and coagulation are closely linked during sepsis. Their interaction can be detrimental to the outcome because of microvascular failure but can also enhance host defense. The role of thrombin therein has not been fully elucidated. Objective We aimed to investigate the contribution of thrombin to the host response during pneumonia-derived sepsis. Methods Mice treated with the specific thrombin inhibitor dabigatran or control chow were infected with the common human sepsis pathogen Klebsiella (K.) pneumoniae via the airways. In subsequent infection experiments, mice were additionally treated with ancrod to deplete fibrinogen. Ex vivo Klebsiella growth was assessed by incubating human whole blood or specific blood components in various conditions with Klebsiella. Results Thrombin inhibition by dabigatran enhanced bacterial outgrowth and spreading, and accelerated mortality. Thrombin inhibition did not influence neutrophil recruitment to the lung or activation or neutrophil extracellular trap formation. Dabigatran reduced D-dimer formation and fibrin deposition in the lung. Fibrin depletion also enhanced bacterial outgrowth and spreading, and thrombin inhibition had no additional effect. Both thrombin and fibrin polymerization inhibited ex vivo Klebsiella outgrowth in human whole blood, which was neutrophil dependent, and the effect of thrombin required the presence of platelets and platelet protease activated receptor-1. In vivo thrombin inhibition reduced platelet-neutrophil complex formation and endothelial cell activation, but did not prevent sepsis-induced thrombocytopenia or organ damage. Conclusions These results suggest that thrombin plays an important role in protective immunity during pneumonia-derived sepsis by fibrin polymerization and enhancement of platelet-neutrophil interactions.

Topics: Animals; Blood Coagulation; Blood Platelets; Cell Communication; Dabigatran; Extracellular Traps; Female; Fibrin; Fibrinogen; Flow Cytometry; Humans; Immune System; Immunity, Innate; Klebsiella Infections; Klebsiella pneumoniae; Lung; Mice; Mice, Inbred C57BL; Microcirculation; Neutrophils; Pneumonia, Bacterial; Sepsis; Thrombin

Severe pneumonia is associated with a local inhibition of fibrinolysis in the lung as reflected by strongly reduced pulmonary plasminogen activator activity.. To study the effect of elevation of local plasminogen activator activity during pneumonia caused by the common respiratory pathogen Klebsiella pneumoniae.. Female C57Bl/6 mice were inoculated intranasally with a replication-defective adenoviral vector expressing human tissue-type plasminogen activator or a control vector 24 h before intranasal infection with K. pneumoniae.. Mice infected with Klebsiella via the airways developed overt pneumonia, which was accompanied by a downregulation of pulmonary tissue-type plasminogen activator levels at protein and mRNA levels. Pulmonary overexpression of human tissue-type plasminogen activator resulted in increased fibrinolytic activity in the lungs during pneumonia, as indicated by higher D-dimer levels and reduced fibrin deposition. Interestingly, overexpression of tissue-type plasminogen activator markedly improved host defense against pneumonia: mice treated with the tissue-type plasminogen activator vector displayed less bacterial growth and dissemination, attenuated distant organ injury and a reduced mortality.. These data demonstrate that local elevation of plasminogen activator activity in the lungs improves host defense against severe gram-negative pneumonia and sepsis.

Topics: Adenoviridae; Administration, Intranasal; Animals; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Genetic Vectors; Humans; Immunity, Innate; Klebsiella Infections; Klebsiella pneumoniae; Lung; Mice; Mice, Inbred C57BL; Pneumonia, Bacterial; Recombinant Fusion Proteins; RNA, Messenger; Sepsis; Tissue Plasminogen Activator; Transgenes

Successful establishment of sepsis by entrapping a dose of 150 colony forming units of Klebsiella pneumoniae in a fibrin clot following implantation into the peritoneal cavity of mice is reported. The dose in the fibrin clot gave 50% mortality in mice, spread over a period of one week. All the infected mice showed positive blood culture up to 6 d post-infection; histopathology revealed inflammatory changes in both liver and spleen. Introduction of K. pneumoniae into experimental mice without entrapment in fibrin clot caused no mortality and blood culture remained positive only up to 2 d; histopathology of liver and spleen throughout the period of study showed relatively mild inflammatory changes, which almost cleared during 14 d post-infection. The use of the fibrin-clot model may thus be considered to be useful in studying both the initial and the persisting stage of infection in the peritoneum, whence a slow release of bacteria into the blood takes place which finally leads to sepsis and septicemia.

Topics: Animals; Disease Models, Animal; Female; Fibrin; Klebsiella Infections; Klebsiella pneumoniae; Liver; Mice; Mice, Inbred Strains; Peritoneal Cavity; Sepsis; Spleen

Of 35 newborn infants who died from an infection 19 had postmortem evidence of massive pulmonary hemorrhage. All but 1 of the 19 had evidence of antimortem formation of intravascular fibrin clots in lung tissue. Seventeen infants had low platelet counts. Of the 11 infants in whom coagulation studies were done, 8 had evidence of disseminated intravascular coagulation (DIC) during life. Vasculitis in the lungs, associated with fibrin clots and hemorrhages, was detected in two infants. It is postulated that sepsis is an important cause of hemorrhage in the newborn, probably as a result of the development of DIC.

Topics: Bacterial Infections; Disseminated Intravascular Coagulation; Escherichia coli Infections; Fibrin; Hemoptysis; Humans; Infant, Newborn; Infant, Newborn, Diseases; Infant, Premature, Diseases; Klebsiella Infections; Lung; Male

Ninety-three postoperative patients 1 day to 13 years of age had blood cultures, limulus lysate assay, determination of fibrin degradation products, white blood cell and platelet counts. Seven groups were studied. The limulus lysate assay was often positive (64%) in the presence of gram negative septicemia but there were false positives and negatives. The tests for fibrin degradation products were inconsistent. The white blood cell count was low in babies with gram negative septicemia. One hundred per cent of the infants with gram negative septicemia had a platelet count below 150,000; 71% below 100,000 (average 67,000 septic babies, 257,000 non-septic babies). The drop in platelet count with gram negative septicemia was abrupt---as much as 222,000 in 24 hours. Platelets increased when therapy was effective. Two children with gram negative septicemia had platelet counts of 50,000 and 20,000. The platelet count for patients with gram positive septicemia was 299,000, and above 150,000 in all children with ruptured and non-ruptured appendicitis and major surgery without gram negative septicemia. It was concluded that serial measurements of platelet count in the postoperative infant and child was a rapid and reliable method for early detection of gram negative septicemia and changes in platelet count in response to treatment was an indicator of the effectiveness of therapy.

Topics: Abdominal Muscles; Adolescent; Appendicitis; Bacteria; Bacterial Infections; Blood Cell Count; Blood Platelets; Child; Child, Preschool; Enterocolitis, Pseudomembranous; Escherichia coli Infections; Fibrin; Gangrene; Humans; Infant; Infant, Newborn; Intestinal Obstruction; Klebsiella Infections; Leukocyte Count; Liver Neoplasms; Platelet Aggregation; Postoperative Complications; Pseudomonas Infections; Sepsis; Time Factors