Pathogenic functions and diagnostic utility of cytokines/chemokines in EHEC-HUS.

Hemolytic - uremic syndrome (HUS) is a severe complication of infection by Shiga toxin (STx)-producing enterohemorrhagic Escherichia coli. Hemolytic - uremic syndrome is defined clinically as a triad of non-immune microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injuries. Neurologic complications such as acute encephalopathy are also observed. In humans, endothelial cells, proximal tubular epithelial cells, mesangial cells, podocytes, intestinal epithelial cells, and monocytes / macrophages are susceptible to STx-mediated injury. Shiga toxin induces the secretion of inflammatory cytokines and chemokines from susceptible cells, including tumor necrosis factor-α interleukin (IL)-1, IL-6, and IL-8. These cytokines and chemokines contribute to the pathogenesis of HUS and encephalopathy by enhancing STx-induced cytotoxicity and inducing inflammatory cell infiltration. Serum cytokine/chemokine levels are therefore useful as indicators of disease activity and predictors of progression from acute kidney injury to chronic kidney disease. Anti-inflammation therapy combined with apheresis to remove excessive cytokines / chemokines and methylprednisolone pulse therapy to suppress cytokine/chemokine production may be an effective treatment regimen for severe E. coli-associated HUS. However, this regimen requires careful monitoring of potential side effects, such as infections, thrombus formation, and hypertension.

[Shiga-toxin associated hemolytic uremic syndrome: How to prevent it?] / Síndrome Hemolítico Urémico asociado a Shigatoxina: ¿Cómo preve nirlo?

Hemolytic uremic syndrome (HUS) associated with intestinal infection by Shiga toxin-producing bacteria, which mainly affects children, can cause severe acute morbidity, chronic sequelae in seve ral organs, and premature death in some of them. Given its zoonotic nature, adequate measures of agricultural management and proper hygiene of what we consume are essential to prevent infection. Once the HUS is triggered, medical management is currently mainly supportive. In recent years, va rious therapeutic strategies have been developed to prevent this disease from occurring or, at least, to mitigate its morbidity and mortality consequences. This article describes specific actions at different levels of prevention of this pathology.

Síndrome hemolítico urémico asociado a Shigatoxina: ¿Cómo prevenirlo? / Shiga-toxin associated hemolytic uremic syndrome: how to prevent it?

Resumen: El síndrome hemolítico urémico (SHU) asociado a infección intestinal por bacterias productoras de Shigatoxina, que afecta principalmente a población infantil, puede causar morbilidad aguda grave, secuelas crónicas en varios órganos, y la muerte prematura en algunos de ellos. Dado su carácter zoonótico, adecuadas medidas de manejo agropecuario y correcta higiene de lo que consumimos es indispensable a la hora de prevenir la infección. Actualmente, una vez gatillado el SHU el manejo es médico y, principalmente, de soporte. En los últimos años diversas estrategias terapéuticas se han ido desarrollando para evitar que esta enfermedad ocurra, o, al menos, que pueda ser atenuada en sus consecuencias de morbi-mortalidad. El presente artículo describe acciones específicas a diferentes niveles de prevención de esta patología.

Abstract Hemolytic uremic syndrome (HUS) associated with intestinal infection by Shiga toxin-producing bacteria, which mainly affects children, can cause severe acute morbidity, chronic sequelae in seve ral organs, and premature death in some of them. Given its zoonotic nature, adequate measures of agricultural management and proper hygiene of what we consume are essential to prevent infection. Once the HUS is triggered, medical management is currently mainly supportive. In recent years, va rious therapeutic strategies have been developed to prevent this disease from occurring or, at least, to mitigate its morbidity and mortality consequences. This article describes specific actions at different levels of prevention of this pathology.

Thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP; also known as Moschcowitz disease) is characterized by the concomitant occurrence of often severe thrombocytopenia, microangiopathic haemolytic anaemia and a variable degree of ischaemic organ damage, particularly affecting the brain, heart and kidneys. Acute TTP was almost universally fatal until the introduction of plasma therapy, which improved survival from <10% to 80-90%. However, patients who survive an acute episode are at high risk of relapse and of long-term morbidity. A timely diagnosis is vital but challenging, as TTP shares symptoms and clinical presentation with numerous conditions, including, for example, haemolytic uraemic syndrome and other thrombotic microangiopathies. The underlying pathophysiology is a severe deficiency of the activity of a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13), the protease that cleaves von Willebrand factor (vWF) multimeric strings. Ultra-large vWF strings remain uncleaved after endothelial cell secretion and anchorage, bind to platelets and form microthrombi, leading to the clinical manifestations of TTP. Congenital TTP (Upshaw-Schulman syndrome) is the result of homozygous or compound heterozygous mutations in ADAMTS13, whereas acquired TTP is an autoimmune disorder caused by circulating anti-ADAMTS13 autoantibodies, which inhibit the enzyme or increase its clearance. Consequently, immunosuppressive drugs, such as corticosteroids and often rituximab, supplement plasma exchange therapy in patients with acquired TTP.

Diminazene aceturate: an antibacterial agent for Shiga-toxin-producing Escherichia coli O157:H7.

The aim of this study was to investigate the bacteriostatic and bactericidal effects of diminazene aceturate (DA) against five strains of pathogenic bacteria and two strains of nonpathogenic bacteria. The results showed that 5 µg/mL of DA suppressed the growth of pathogenic Escherichia coli by as much as 77% compared with the controls. Enterohemorrhagic E. coli EDL933 (an E. coli O157:H7 strain) was the most sensitive to DA with a minimum inhibitory concentration of 20 µg/mL. Additional investigations showed that DA induced the highest level of intracellular reactive oxygen species in EDL933. A positive correlation between the reactive oxygen species levels and DA concentration was demonstrated. DA (5 µg/mL) was also a potent uncoupler, inducing a stationary phase collapse (70%-75%) in both strains of E. coli O157:H7. Further investigation showed that the collapse was due to the NaCl:DA ratio in the broth and was potassium ion dependent. A protease screening assay was conducted to elucidate the underlying mechanism. It was found that at neutral pH, the hydrolysis of H-Asp-pNA increased by a factor of 2-3 in the presence of DA, implying that DA causes dysregulation of the proton motive force and a decrease in cellular pH. Finally, a commercial verotoxin test showed that DA did not significantly increase toxin production in EDL933 and was a suitable antibacterial agent for Shiga-toxin-producing E. coli.

Thrombotic microangiopathies: from animal models to human disease and cure.

Thrombotic microangiopathies are a group of microvascular disorders, with reduced organ perfusion and hemolytic anemia. The two most relevant conditions characterized by thrombotic microangiopathic anemia (TMA) are thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). In TTP, systemic microvascular aggregation of platelets causes ischemia in the brain and other organs. In HUS, platelet-fibrin thrombi predominantly occlude the renal circulation. TTP can be inherited due to deficiencies in the activity of von Willebrand factor cleaving protease (ADAMTS13) or acquired due to the presence of autoantibodies directed against ADAMTS13. The majority of HUS cases are secondary to infections by strains of Escherichia coli that produce Shiga-like toxins (Stx-HUS), while about 5- 10% of all cases are classified as atypical HUS (aHUS). Genetically derived impaired regulation of the complement system is associated with aHUS. Infusion or the exchange of fresh frozen plasma have ameliorated the prognosis of TMA; however, no specific therapies aimed at preventing or limiting the microangiopathic process have been proven to affect the course of TMA. Large mammals, small animal models, knockout and transgenic mouse models of TTP and both Stx-HUS and aHUS have been developed and have provided outstanding contributions to nearly all areas of TMA research. A better understanding of the key clinical features of the diseases and of the importance of genetic and/or environmental factors involved in the pathogenesis of the diseases have been obtained. These animal models have also allowed the set up of protocols aimed at ameliorating the clinical approach to patients and for the development of new drugs and vaccines.

Shiga toxin B subunits induce VWF secretion by human endothelial cells and thrombotic microangiopathy in ADAMTS13-deficient mice.

Diarrhea-associated hemolytic uremic syndrome (D+HUS) is the most common cause of acute renal failure among children. Renal damage in D+HUS is caused by Shiga toxin (Stx), which is elaborated by Shigella dysenteriae and certain strains of Escherichia coli, in North America principally E coli O157:H7. Recent studies demonstrate that Stx also induces von Willebrand factor (VWF) secretion by human endothelial cells and causes thrombotic thrombocytopenic purpura, a disease with similarities to D+HUS, in Adamts13(-/-) mice. Stx occurs in 2 variants, Stx1 and Stx2, each of which is composed of 1 catalytically active A subunit that is responsible for cytotoxicity, and 5 identical B subunits that mediate binding to cell-surface globo-triaosylceramide. We now report that B subunits from Stx1 or Stx2 can stimulate the acute secretion of VWF in the absence of the cytotoxic A subunit. This rapid effect requires binding and clustering of globotriaosylceramide, and depends on plasma membrane cholesterol and caveolin-1 but not clathrin. Furthermore, similar to Stx2 holotoxin, the isolated Stx2B subunits induce thrombotic microangiopathy in Adamts13(-/-) mice. These results demonstrate the existence of a novel Stx B-induced lipid raft-dependent signaling pathway in endothelial cells that may be responsible for some of the biological effects attributed previously to the cytotoxic Stx A subunit.

[Haemolytic uremic syndrome and thrombotic thrombocytopenic purpura: classification based on molecular etiology and review of recent developments in diagnostics]. / A hemolitikus urémiás szindróma és a trombotikus thrombocytopeniás purpura molekuláris szemléletu klasszifikációja és diagnosztikájuknak aktuális kérdései.

Haemolytic uremic syndrome and thrombotic thrombocytopenic purpura are overlapping clinical entities based on historical classification. Recent developments in the unfolding of the pathomechanisms of these diseases resulted in the creation of a molecular etiology-based classification. Understanding of some causative relationships yielded detailed diagnostic approaches, novel therapeutic options and thorough prognostic assortment of the patients. Although haemolytic uremic syndrome and thrombotic thrombocytopenic purpura are rare diseases with poor prognosis, the precise molecular etiology-based diagnosis might properly direct the therapy of the affected patients. The current review focuses on the theoretical background and detailed description of the available diagnostic possibilities, and some practical information necessary for the interpretation of their results.

Environmental prevention of human disease from verocytotoxin-producing Escherichia coli.

Verocytotoxin-producing Escherichia coli (VTEC) haemolytic uraemic syndrome (HUS) is an important cause of mortality and renal failure worldwide. For those patients who need medical attention, no treatment aside from supportive care has proven effective for this disease. This has prompted a broader look at environmental prevention, with a particular emphasis on the transmission of bacteria from animal carriers to human beings. Here, we review animal- and meat-handling strategies to reduce the burden of VTEC human disease.

Pathogenesis and prognosis of thrombotic microangiopathy.

Thrombotic microangiopathy (TMA) is a clinicopathological syndrome characterized by thrombosis formation in the microvasculature of various organs. Included in the broad category of TMA are the hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Typical HUS is caused by Escherichia coli O157:H7, which produces the Shiga-like toxins; Stx-1 and Stx-2. In addition to damaging endothelial cells via the inhibition of protein synthesis, Shiga-like toxins also activate endothelial cells to produce inflammatory mediators, amplifying the prothrombogenic state. Although most patients with typical HUS recover renal functions, recent analysis has shown that typical HUS is not a benign disease in the long term. Genetic abnormalities of complement regulatory proteins predispose patients to atypical HUS. Mutations in factor H, membrane cofactor protein, and factor I are known to be associated with atypical HUS. Atypical HUS forms have a poor outcome and show recurrent and progressive courses. Autoimmune IgG inhibitors of a disintegrin and metalloprotease, with thrombospodin-1-like domains (ADAMTS) 13 and mutations of the ADAMTS13 gene lead to the development of TTP. Without treatment, TTP is associated with a very high mortality rate. As it is for atypical HUS, plasma exchange is currently the most feasible treatment for TTP. Etiological diagnosis at the bedside and the development of disease-specific therapeutic modalities will enable us to optimize the management of patients with TMA and improve their prognosis in the future.

Secondary sclerosing cholangitis and portal hypertension after O157 enterocolitis: Extremely rare complications of hemolytic uremic syndrome.

The authors experienced an extremely rare case of secondary sclerosing cholangitis and portal hypertension developed as late complications of hemolytic uremic syndrome (HUS) owing to Escherichia coli O157:H7 in a 2-year-old boy. HUS after E coli O157 infection is the most frequent cause of acute renal failure in childhood and occasionally is accompanied by extrarenal complications such as encephalopathy, cardiomyopathy, ischemic colitis, and pancreatitis. Rarely, late colonic stenosis may develop secondary to the ischemic damage. Sclerosing cholangitis and subsequent cirrhosis with portal hypertension are very uncommon as late complications of HUS. To our knowledge, such a case has not been previously reported in the literature. J Pediatr Surg 36:1838-1840.

[Hemolytic-uremic syndrome: microbiological aspects]. / Syndrome hémolytique et urémique: aspects microbiologiques.

Escherichia coli O157: H7 became an important pathogen starting in the early 1980s. It has caused epidemics and sporadic cases of often bloody diarrhea which may progress to severe hemolytic and uremic syndrome or thrombotic thrombocytopenia purpura. E. coli O157: H7 is mainly transmitted in food, water and interhuman transmission, but direct animal-to-man transmission has also been documented. E. coli O157: H7 can adhere tightly to the enterocyte brush border (eae gene) and produce verotoxins or Shiga-like toxins and hemolysine (ehxA gene). Diagnosis of E. coli O157: H7 infections is based on evidencing the germ in stools and/or by identifying the genes coding for verotoxins or by serology which increased serum titre of specific antilipopolysaccharide antibodies. Antidiarrheal drugs and antibiotics have little place in the treatment of bloody diarrhea. This public health problem, requires careful identification of animal reservoirs and improved population education in food hygiene.