EspP, an Extracellular Serine Protease from Enterohemorrhagic E. coli, Reduces Coagulation Factor Activities, Reduces Clot Strength, and Promotes Clot Lysis.

BACKGROUND: EspP (E. coli secreted serine protease, large plasmid encoded) is an extracellular serine protease produced by enterohemorrhagic E. coli (EHEC) O157:H7, a causative agent of diarrhea-associated Hemolytic Uremic Syndrome (D+HUS). The mechanism by which EHEC induces D+HUS has not been fully elucidated. OBJECTIVES: We investigated the effects of EspP on clot formation and lysis in human blood. METHODS: Human whole blood and plasma were incubated with EspP(WT )at various concentrations and sampled at various time points. Thrombin time (TT), prothrombin time (PT), and activated partial thromboplastin time (aPTT), coagulation factor activities, and thrombelastgraphy (TEG) were measured. RESULTS AND CONCLUSIONS: Human whole blood or plasma incubated with EspP(WT) was found to have prolonged PT, aPTT, and TT. Furthermore, human whole blood or plasma incubated with EspP(WT) had reduced activities of coagulation factors V, VII, VIII, and XII, as well as prothrombin. EspP did not alter the activities of coagulation factors IX, X, or XI. When analyzed by whole blood TEG, EspP decreased the maximum amplitude of the clot, and increased the clot lysis. Our results indicate that EspP alters hemostasis in vitro by decreasing the activities of coagulation factors V, VII, VIII, and XII, and of prothrombin, by reducing the clot strength and accelerating fibrinolysis, and provide further evidence of a functional role for this protease in the virulence of EHEC and the development of D+HUS.

Pathological splenic rupture: a rare complication of chronic myelomonocytic leukemia.

Chronic myelomonocytic leukemia (CMML) is an uncommon disorder characterized by monocytosis of the peripheral blood, absence of the Philadelphia chromosome, fewer than 20% blasts, and one or more lineages showing dysplastic features. Splenomegaly is frequently seen and may be massive. A 56-year-old man with stable CMML and moderate splenomegaly presented to the emergency department with generalized abdominal pain and abrupt drop in hemoglobin. Abdominal imaging revealed splenic rupture and emergency splenectomy was undertaken, with complete recovery. Atraumatic rupture of the spleen has rarely been reported as a complication of CMML or other myelodysplastic disorders. This report should alert physicians to consider this diagnosis in patients with CMML and acute abdominal pain.