Steroids in the hemolytic uremic syndrome

Prognostic factors among patients with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome: A retrospective cohort study using a nationwide inpatient database in Japan

INTRODUCTION

Shiga toxin-producing Escherichia coli (STEC) causes hemorrhagic colitis and hemolytic uremic syndrome (STEC-HUS). Understanding its prognostic factors is essential for immediate interventions. We examined early-phase unfavorable prognostic factors among patients with STEC-HUS using a nationwide database.

MATERIAL AND METHODS

This is a retrospective cohort study to analyze practice patterns and identify prognostic factors among patients with STEC-HUS. We used the Diagnosis Procedure Combination Database, which includes approximately half of the acute-care hospitalized patients in Japan. We enrolled patients who were hospitalized for STEC-HUS from July 2010 to March 2020. The composite unfavorable outcome included in-hospital death, mechanical ventilation, dialysis, and rehabilitation at discharge. Unfavorable prognostic factors were assessed using a multivariable logistic regression model.

RESULTS

We included 615 patients with STEC-HUS (median age, 7 years). Of them, 30 (4.9%) patients had acute encephalopathy and 24 (3.9%) died within 3 months of admission. Unfavorable composite outcome was observed in 124 (20.2%) patients. Significant unfavorable prognostic factors were age of 18 years or older, methylprednisolone pulse therapy, antiepileptic drug administration, and respiratory support within 2 days of admission.

DISCUSSION

Patients requiring early steroid pulse therapy, antiepileptic drugs, and respiratory support were considered to be in poor general condition; such patients should receive aggressive intervention to avoid worse outcomes.

Steroid Pulse Therapy for Severe Central Nervous System Involvement in Shiga Toxin-Producing Escherichia coli-Related Hemolytic Uremic Syndrome

We report on the case of a 7-year-old boy with Shiga toxin-producing Escherichia coli-related hemolytic uremic syndrome (STEC-HUS), initially presenting with abdominal pain as the only clinical feature and thus requiring differential diagnosis with a surgical emergency. Diagnosis of STEC-HUS was made with the appearance of bloody diarrhea and renal function impairment, and the clinical picture rapidly progressed to multiorgan failure. Relatively late and severe central nervous system (CNS) involvement was present, characterized by subacute encephalitis progressing to coma, which became apparent when the acute phase of thrombotic microangiopathy was resolving. Therefore, neurologic manifestations were thought to be related to reperfusion damage to the CNS and high-dose IV steroid pulse therapy was empirically administered. Following this therapeutic scheme, neurologic involvement resolved with no sequelae. This case offers several points of discussion on the clinical presentation and the diagnostic approach to STEC-HUS, on the related neurologic complications, and on a novel approach to their management.

Severely ill pediatric patients with Shiga toxin-associated hemolytic uremic syndrome (STEC-HUS) who suffered from multiple organ involvement in the early stage

BACKGROUND

Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (STEC-HUS) is the main cause of pediatric acute kidney injury (AKI) in Argentina. Endothelial injury is the trigger event in the microangiopathic process. The host inflammatory response to toxin and E. coli lipopolysaccharide (LPS) is involved in disease pathophysiology.

METHODS

This retrospective study describes pediatric STEC-HUS patients with multiorgan involvement at the initial phase of disease. A retrospective study of critically ill HUS patients with evidence of E. coli infection was conducted through a period of 15 years.

RESULTS

Forty-four patients 35.4 ± 4.1 months were admitted to the intensive care unit for 21 ± 2 days. Mechanical ventilation was required in 41 patients, early inotropic support in 37, and 28 developed septic shock. Forty-one patients required kidney replacement therapy for 12 ± 1 days. Forty-one patients showed neurological dysfunction. Dilated cardiomyopathy was demonstrated in 3 patients, left ventricular systolic dysfunction in 4, and hypertension in 17. Four patients had pulmonary hemorrhage, and acute respiratory distress syndrome in 2. Colectomy for transmural colonic necrosis was performed in 3 patients. Thirty-seven patients were treated with therapeutic plasma exchange, and 28 patients received methylprednisolone (10 mg/kg for 3 days). Of the surviving 32 patients, neurological sequelae were seen in 11 and chronic kidney failure in 5.

CONCLUSIONS

Severe clinical outcome at onset suggests an amplified inflammatory response after exposure to Shiga toxin and/or E. coli LPS. STEC-HUS associated with severe neurological involvement, hemodynamic instability, and AKI requires intensive care and focused therapy.

Shiga Toxin-Associated Hemolytic Uremic Syndrome: Specificities of Adult Patients and Implications for Critical Care Management

Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (STEC-HUS) is a form of thrombotic microangiopathy secondary to an infection by an enterohemorrhagic E. coli. Historically considered a pediatric disease, its presentation has been described as typical, with bloody diarrhea at the forefront. However, in adults, the clinical presentation is more diverse and makes the early diagnosis hazardous. In this review, we review the epidemiology, most important outbreaks, physiopathology, clinical presentation and prognosis of STEC-HUS, focusing on the differential features between pediatric and adult disease. We show that the clinical presentation of STEC-HUS in adults is far from typical and marked by the prevalence of neurological symptoms and a poorer prognosis. Of note, we highlight knowledge gaps and the need for studies dedicated to adult patients. The differences between pediatric and adult patients have implications for the treatment of this disease, which remains a public health threat and lack a specific treatment.

Therapeutic Strategies to Protect the Central Nervous System against Shiga Toxin from Enterohemorrhagic Escherichia coli

Infection with Shiga toxin-producing Escherichia coli (STEC) may cause hemorrhagic colitis, hemolytic uremic syndrome (HUS) and encephalopathy. The mortality rate derived from HUS adds up to 5% of the cases, and up to 40% when the central nervous system (CNS) is involved. In addition to the well-known deleterious effect of Stx, the gram-negative STEC releases lipopolysaccharides (LPS) and may induce a variety of inflammatory responses when released in the gut. Common clinical signs of severe CNS injury include sensorimotor, cognitive, emotional and/or autonomic alterations. In the last few years, a number of drugs have been experimentally employed to establish the pathogenesis of, prevent or treat CNS injury by STEC. The strategies in these approaches focus on: 1) inhibition of Stx production and release by STEC, 2) inhibition of Stx bloodstream transport, 3) inhibition of Stx entry into the CNS parenchyma, 4) blockade of deleterious Stx action in neural cells, and 5) inhibition of immune system activation and CNS inflammation. Fast diagnosis of STEC infection, as well as the establishment of early CNS biomarkers of damage, may be determinants of adequate neuropharmacological treatment in time.

Shiga Toxin-Associated Hemolytic Uremic Syndrome: A Narrative Review

The severity of human infection by one of the many Shiga toxin-producing Escherichia coli (STEC) is determined by a number of factors: the bacterial genome, the capacity of human societies to prevent foodborne epidemics, the medical condition of infected patients (in particular their hydration status, often compromised by severe diarrhea), and by our capacity to devise new therapeutic approaches, most specifically to combat the bacterial virulence factors, as opposed to our current strategies that essentially aim to palliate organ deficiencies. The last major outbreak in 2011 in Germany, which killed more than 50 people in Europe, was evidence that an effective treatment was still lacking. Herein, we review the current knowledge of STEC virulence, how societies organize the prevention of human disease, and how physicians treat (and, hopefully, will treat) its potentially fatal complications. In particular, we focus on STEC-induced hemolytic and uremic syndrome (HUS), where the intrusion of toxins inside endothelial cells results in massive cell death, activation of the coagulation within capillaries, and eventually organ failure.

Hemolytic Uremic Syndrome: An Increasingly Recognized Public Health Problem

A 28-year-old man was referred and admitted to our hospital due to Escherichia coli O157-mediated hemorrhagic colitis with severe thrombocytopenia. A systemic workup concluded that the patient had acute pancreatitis as well as hemolytic uremic syndrome. The patient was ultimately discharged, with his platelet count having recovered. Our case serves an illustrative example of potentially serious complications of an increasingly recognized public health problem. Systemic studies on this topic are insufficient, and we strongly recommend the further accumulation of more experiences like ours. Several diagnostic and management concerns that emerged in this case are also discussed.

A devastating case of diarrhea-associated hemolytic uremic syndrome associated with extensive cerebral infarction; why we need to do better

A 4-year-old girl with diarrhea-associated hemolytic uremic syndrome (D+HUS) was transferred to the PICU of our center due to deteriorating renal function and neurological involvement. On admission, a comatous child was seen with hypoventilation and she was placed on mechanical ventilation. Hemodialysis was commenced but plasma exchange was discontinued due to repeated hypersensitivity reactions. A trial of eculizumab was given in light of the worsening of her neurologic condition with development of a pyramidal syndrome and deepening of the coma. Hematological and renal improvement were noted but severe neurologic involvement persisted. MRI revealed extensive bilateral zones of corticocerebral infarction and neurological damage proved to be irreversible. Diarrhea-associated hemolytic uremic syndrome is a common cause of Acute Kidney Injury associated with severe short- and long-term complications. Neurologic involvement is frequent but often reversible. Currently, no effective treatment strategies are available and a paucity of data exists concerning the efficacy of potential treatment options such as early plasma exchange, eculizumab, and high dose corticosteroids. A concerted effort is needed to early identify patients at risk for poor outcome with trials aimed at evaluating the efficacy of potential treatment options for this subgroup.

Treatment and management of children with haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS), comprising microangiopathic haemolytic anaemia, thrombocytopaenia and acute kidney injury, remains the leading cause of paediatric intrinsic acute kidney injury, with peak incidence in children aged under 5 years. HUS most commonly occurs following infection with Shiga toxin-producing Escherichia coli (STEC-HUS). Additionally, HUS can occur as a result of inherited or acquired dysregulation of the alternative complement cascade (atypical HUS or aHUS) and in the setting of invasive pneumococcal infection. The field of HUS has been transformed by the discovery of the central role of complement in aHUS and the dawn of therapeutic complement inhibition. Herein, we address these three major forms of HUS in children, review the latest evidence for their treatment and discuss the management of STEC infection from presentation with bloody diarrhoea, through to development of fulminant HUS.

Mechanism of inhibition of Shiga-toxigenic Escherichia coli SubAB cytotoxicity by steroids and diacylglycerol analogues

Shiga toxigenic Escherichia coli (STEC) are responsible for a worldwide foodborne disease, which is characterized by severe bloody diarrhea and hemolytic uremic syndrome (HUS). Subtilase cytotoxin (SubAB) is a novel AB₅ toxin, which is produced by Locus for Enterocyte Effacement (LEE)-negative STEC. Cleavage of the BiP protein by SubAB induces endoplasmic reticulum (ER) stress, followed by induction of cytotoxicity in vitro or lethal severe hemorrhagic inflammation in mice. Here we found that steroids and diacylglycerol (DAG) analogues (e.g., bryostatin 1, Ingenol-3-angelate) inhibited SubAB cytotoxicity. In addition, steroid-induced Bcl-xL expression was a key step in the inhibition of SubAB cytotoxicity. Bcl-xL knockdown increased SubAB-induced apoptosis in steroid-treated HeLa cells, whereas SubAB-induced cytotoxicity was suppressed in Bcl-xL overexpressing cells. In contrast, DAG analogues suppressed SubAB activity independent of Bcl-xL expression at early time points. Addition of Shiga toxin 2 (Stx2) with SubAB to cells enhanced cytotoxicity even in the presence of steroids. In contrast, DAG analogues suppressed cytotoxicity seen in the presence of both toxins. Here, we show the mechanism by which steroids and DAG analogues protect cells against SubAB toxin produced by LEE-negative STEC.

The 2011 German Enterohemorrhagic Escherichia Coli O104:H4 Outbreak-The Danger Is Still Out There

Enterohemorrhagic Escherichia coli (EHEC) are Shiga toxin (Stx) producing bacteria causing a disease characterized by bloody (or non-bloody) diarrhea, which might progress to hemolytic uremic syndrome (HUS). EHEC O104:H4 caused the largest ever recorded EHEC outbreak in Germany in 2011, which in addition showed the so far highest incidence rate of EHEC-related HUS worldwide. The aggressive outbreak strain carries an unusual combination of virulence traits characteristic to both EHEC-a chromosomally integrated Stx-encoding bacteriophage, and enteroaggregative Escherichia coli-pAA plasmid-encoded aggregative adherence fimbriae mediating its tight adhesion to epithelia cells. There are currently still open questions regarding the 2011 EHEC outbreak, e.g., with respect to the exact molecular mechanisms resulting in the hypervirulence of the strain, the natural reservoir of EHEC O104:H4, and suitable therapeutic strategies. Nevertheless, our knowledge on these issues has substantially expanded since 2011. Here, we present an overview of the epidemiological, clinical, microbiological, and molecular biological data available on the 2011 German EHEC O104:H4 outbreak.

Hemolytic Uremic Syndrome-associated Encephalopathy Successfully Treated with Corticosteroids

The encephalopathy that occurs in association with hemolytic uremic syndrome (HUS), which is caused by enterohemorrhagic Escherichia coli (E. coli), has a high mortality rate and patients sometimes present sequelae. We herein describe the case of a 20-year-old woman who developed encephalopathy during the convalescent stage of HUS caused by E.coli O26. Hyperintense lesions were detected in the pons, basal ganglia, and cortex on diffusion-weighted brain MRI. From the onset of HUS encephalopathy, we treated the patient with methylprednisolone (mPSL) pulse therapy alone. Her condition improved, and she did not present sequelae. Our study shows that corticosteroids appear to be effective for the treatment of some patients with HUS encephalopathy.

Blood urea nitrogen to serum creatinine ratio is an accurate predictor of outcome in diarrhea-associated hemolytic uremic syndrome, a preliminary study

Diarrhea-associated hemolytic uremic syndrome (D+HUS) is a common thrombotic microangiopathy during childhood and early identification of parameters predicting poor outcome could enable timely intervention. This study aims to establish the accuracy of BUN-to-serum creatinine ratio at admission, in addition to other parameters in predicting the clinical course and outcome. Records were searched for children between 1 January 2008 and 1 January 2015 admitted with D+HUS. A complicated course was defined as developing one or more of the following: neurological dysfunction, pancreatitis, cardiac or pulmonary involvement, hemodynamic instability, and hematologic complications while poor outcome was defined by death or development of chronic kidney disease. Thirty-four children were included from which 11 with a complicated disease course/poor outcome. Risk of a complicated course/poor outcome was strongly associated with oliguria (p = 0.000006) and hypertension (p = 0.00003) at presentation. In addition, higher serum creatinine (p = 0.000006) and sLDH (p = 0.02) with lower BUN-to-serum creatinine ratio (p = 0.000007) were significantly associated with development of complications. A BUN-to-sCreatinine ratio ≤40 at admission was a sensitive and highly specific predictor of a complicated disease course/poor outcome.

CONCLUSION

A BUN-to-serum Creatinine ratio can accurately identify children with D+HUS at risk for a complicated course and poor outcome. What is Known: • Oliguria is a predictor of poor long-term outcome in D+HUS What is New: • BUN-to-serum Creatinine ratio at admission is an entirely novel and accurate predictor of poor outcome and complicated clinical outcome in D+HUS • Early detection of the high risk group in D+HUS enabling early treatment and adequate monitoring.

Natural killer T (NKT) cells accelerate Shiga toxin type 2 (Stx2) pathology in mice

Shiga toxin-producing Escherichia coli (STEC) is a leading cause of childhood renal disease Hemolytic Uremic Syndrome (HUS). The involvement of renal cytokines and chemokines is suspected to play a critical role in disease progression. In current article, we tested the hypothesis that NKT cells are involved in Stx2-induced pathology in vivo. To address this hypothesis we compared Stx2 toxicity in WT and CD1 knockout (KO) mice. In CD1KO mice, which lack natural killer T (NKT) cells, Stx2-induced pathologies such as weight loss, renal failure, and death were delayed. In WT mice, Stx2-specific selective increase in urinary albumin occurs in later time points, and this was also delayed in NKT cell deficient mice. NKT cell-associated cytokines such as IL-2, IL-4, IFN-γ, and IL-17 were detected in kidney lysates of Stx2-injected WT mice with the peak around 36 h after Stx2 injection. In CD1KO, there was a delay in the kinetics, and increases in these cytokines were observed 60 h post Stx2 injection. These data suggest that NKT cells accelerate Stx2-induced pathology in mouse kidneys. To determine the mechanism by which NKT cells promote Stx2-associated disease, in vitro studies were performed using murine renal cells. We found that murine glomerular endothelial cells and podocytes express functional CD1d molecules and can present exogenous antigen to NKT cells. Moreover, we observed the direct interaction between Stx2 and the receptor Gb₃ on the surface of mouse renal cells by 3D STORM-TIRF which provides single molecule imaging. Collectively, these data suggest that Stx2 binds to Gb₃ on renal cells and leads to aberrant CD1d-mediated NKT cell activation. Therefore, strategies targeting NKT cells could have a significant impact on Stx2-associated renal pathology in STEC disease.

Validation of treatment strategies for enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome: case-control study

OBJECTIVE

To evaluate the effect of different treatment strategies on enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome.

DESIGN

Multicentre retrospective case-control study.

SETTING

23 hospitals in northern Germany.

PARTICIPANTS

298 adults with enterohaemorrhagic E coli induced haemolytic uraemic syndrome.

MAIN OUTCOME MEASURES

Dialysis, seizures, mechanical ventilation, abdominal surgery owing to perforation of the bowel or bowel necrosis, and death.

RESULTS

160 of the 298 patients (54%) temporarily required dialysis, with only three needing treatment long term. 37 patients (12%) had seizures, 54 (18%) required mechanical ventilation, and 12 (4%) died. No clear benefit was found from use of plasmapheresis or plasmapheresis with glucocorticoids. 67 of the patients were treated with eculizumab, a monoclonal antibody directed against the complement cascade. No short term benefit was detected that could be attributed to this treatment. 52 patients in one centre that used a strategy of aggressive treatment with combined antibiotics had fewer seizures (2% v 15%, P = 0.03), fewer deaths (0% v 5%, p = 0.029), required no abdominal surgery, and excreted E coli for a shorter duration.

CONCLUSIONS

Enterohaemorrhagic E coli induced haemolytic uraemic syndrome is a severe self limiting acute condition. Our findings question the benefit of eculizumab and of plasmapheresis with or without glucocorticoids. Patients with established haemolytic uraemic syndrome seemed to benefit from antibiotic treatment and this should be investigated in a controlled trial.

Management of hemolytic uremic syndrome

2011 has been a special year for hemolytic uremic syndrome (HUS): on the one hand, the dramatic epidemic of Shiga toxin producing E. coli -associated HUS in Germany brought the disease to the attention of the general population, on the other hand it has been the year when eculizumab, the first complement blocker available for clinical practice, was demonstrated as the potential new standard of care for atypical HUS. Here we review the therapeutic options presently available for the various forms of hemolytic uremic syndrome and show how recent knowledge has changed the therapeutic approach and prognosis of atypical HUS.

Microangiopathic disorders in pregnancy

Microangiopathic disorders present with thrombocytopenia, hemolytic anemia, and multiorgan damage. In pregnancy, these disorders present a challenge both diagnostically and therapeutically, with widely overlapping clinical scenarios and disparate treatments. Although rare, a clear understanding of these diseases is important because devastating maternal and fetal outcomes may ensue if there is misdiagnosis and improper treatment. Microangiopathic disorders presenting in pregnancy are thus best assessed and treated by both obstetric and hematology teams. As a better understanding of the pathophysiology underlying each of the disease processes is gained, new diagnostic testing and therapies will be available, which will lead to improved outcomes.

Hemolytic uremic syndrome: pathogenesis and update of interventions

The typical form of hemolytic uremic syndrome (HUS) is the major complication of Shiga toxin-producing Escherichia coli infections. HUS is a critical health problem in Argentina since it is the main cause of acute renal failure in children and the second cause of chronic renal failure, accounting for 20% of renal transplants in children and adolescents in Argentina. Despite extensive research in the field, the mainstay of treatment for patients with HUS is supportive therapy, and there are no specific therapies preventing or ameliorating the disease course. In this review, we present the current knowledge about pathogenic mechanisms and discuss traditional and innovative therapeutic approaches, with special focus in Argentinean contribution. The hope that a better understanding of transmission dynamics and pathogenesis of this disease will produce better therapies to prevent the acute mortality and the long-term morbidity of HUS is the driving force for intensified research.

Escherichia coli O157: what every internist and gastroenterologist should know

Infections with Escherichia coli O157:H7 have gained media attention in recent years because of cases associated with unusual sources (eg, produce and swimming pools). Although most adults recover without sequelae, children and the elderly are more likely to develop complications (eg, hemolytic uremic syndrome and death). The diagnosis typically has been made by culture; however, newer hand-held immunoassays and polymerase chain reaction technology have led to more rapid detection of this important pathogen in stools, food, and water. Treatment is largely supportive; nonetheless, new methods to neutralize or bind toxin, such as probiotics, monoclonal antibodies, and recombinant bacteria, are showing promise to treat patients infected with E. coli O157:H7. The role of antibiotics in relation to this condition remains unclear.

Interventions for haemolytic uraemic syndrome and thrombotic thrombocytopenic purpura

BACKGROUND

Haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are related conditions with similar clinical features of variable severity. Survival of patients with HUS and TTP has improved greatly over the past two decades with improved supportive care for patients with HUS and by the use of plasma exchange (PE) with fresh frozen plasma (FFP) for patients with TTP. Separate pathogenesis of these two disorders has become more evident, but management overlaps.

OBJECTIVES

To evaluate the benefits and harms of different interventions for HUS and TTP separately, in patients of all ages.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), conference proceedings, reference lists of articles and text books and contact with investigators were used to identify relevant studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) evaluating any interventions for HUS or TTP in patients of all ages.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data and evaluated study reporting quality using standard Cochrane criteria. Analysis was undertaken using a random effects model and results expressed as risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

For TTP, we found six RCTs (331 participants) evaluating PE with FFP as the control. Interventions tested included antiplatelet therapy (APT) plus PE with FFP, FFP transfusion and PE with cryosupernatant plasma (CSP). Two studies compared plasma infusion (PI) to PE with FFP and showed a significant increase in failure of remission at two weeks (RR 1.48, 95% 1.12 to 1.96) and all-cause mortality (RR 1.91, 95% 1.09 to 3.33) in the PI group. Seven RCTs were undertaken in children with HUS. None of the assessed interventions used (FFP transfusion, heparin with or without urokinase or dipyridamole, shiga toxin binding protein and steroids) were superior to supportive therapy alone, for all-cause mortality, neurological/extrarenal events, renal biopsy changes, proteinuria or hypertension at the last follow-up visit. Bleeding was significantly higher in those receiving anticoagulation therapy compared to supportive therapy alone (RR 25.89, 95% CI 3.67 to 182.83).

AUTHORS' CONCLUSIONS

PE with FFP is still the most effective treatment available for TTP. For patients with HUS, supportive therapy including dialysis is still the most effective treatment. All studies in HUS have been conducted in the diarrhoeal form of the disease. There were no RCTs evaluating the effectiveness of any interventions on patients with atypical HUS who have a more chronic and relapsing course.

Shiga toxin 2 affects the central nervous system through receptor globotriaosylceramide localized to neurons

Affinity-purified Shiga toxin (Stx) 2 given intraperitoneally to mice caused weight loss and hind-limb paralysis followed by death. Globotriaosylceramide (Gb(3)), the receptor for Stx2, was localized to neurons of the central nervous system (CNS) of normal mice. Gb3 was not found in astrocytes or endothelial cells of the CNS. In human cadaver CNS, we found Gb(3) in neurons and endothelial cells. Mouse Gb(3) localization was confirmed by immunoelectron microscopy. In Stx2-exposed mice, anti-Stx2-gold immunoreaction was positive in neurons. During paralysis, after Stx2 injection, multiple glial nuclei were observed surrounding motoneurons by electron microscopy. Also revealed was a lamellipodia-like process physically inhibiting the synaptic connection of motoneurons. Ca2+ imaging of cerebral astrocytic end-feet in Stx2-treated mouse brains suggested that the toxin increased neurotransmitter release from neurons. In this article, we propose that the neuron is a primary target of Stx2, affecting neuronal function and leading to paralysis.

Prevention and treatment of enterohemorrhagic Escherichia coli infections in humans

Infections with enterohemorrhagic Escherichia coli (EHEC) result in various clinical symptoms and outcomes ranging from watery or bloody diarrhea to the life-threatening hemolytic-uremic syndrome (HUS). Shiga toxins (Stxs) are supposed to play a major role in the pathogenesis of EHEC infections; however, the role of other putative virulence factors is not fully elucidated. So far, there is only supportive therapy available for the treatment of both EHEC-associated diarrhea and HUS. Antibiotic therapy for the treatment of EHEC-associated diarrhea is discussed. In recent years other therapeutic strategies have been developed, including Gb3 receptor analogues, that bind Stx in the gut or in the circulation, passive immunization with Stx-neutralizing monoclonal antibodies, or active immunization with Stx1 And Stx2 toxoids as a preventive procedure. These approaches have been demonstrated to be effective in animal models but clinical trials are lacking.

A novel pentamer versus pentamer approach to generating neutralizers of verotoxin 1

Verotoxins (VTs), or shiga-like toxins, are produced by enterohemorrhagic Escherichia coli (EHEC), which cause hemorrhagic colitis and hemolytic uremic syndrome. VTs are the major virulence factors in EHEC infection due to their cytotoxicity to various types of cells. Here, we present a novel type of VT neutralizer based on pentavalent single-domain antibodies, or pentabodies. Two single-domain antibodies (sdAbs) specific for the receptor binding sites of the B subunit of VT1 (VT1B) were isolated from a naïve llama phage display library. These two sdAbs were pentamerized to generate pentameric VT neutralizers, VTI-1 and VTI-3. Both VT neutralizers bound wild type VT1B specifically with superior functional affinity. In vitro neutralization assays showed that VTI-1 and VTI-3 were able to neutralize 90% and 40%, respectively, of the cytotoxicity caused by VT1. This effort provides the basis of a novel type of VT neutralizer that can potentially be produced at a relatively low cost.

Haemolytic uraemic syndrome: an overview

Haemolytic uraemic syndrome (HUS) is the most common cause of acute renal failure in children. The syndrome is defined by triad of microangiopathic haemolytic anaemia, thrombocytopenia and acute renal failure (ARF). Incomplete HUS is ARF with either haemolytic anaemia or thrombocytopenia. HUS is classified into two subgroups. Typical HUS usually occurs after a prodrome of diarrhoea (D+HUS), and atypical (sporadic) HUS (aHUS), which is not associated with diarrhoea (D-HUS). The majority of D+HUS worldwide is caused by Shiga toxin-producing Esherichia coli (STEC), type O157:H7, transmitted to humans via different vehicles. Currently there are no specific therapies preventing or ameliorating the disease course. Although there are new therapeutic modalities in the horizon for D+HUS, present recommended therapy is merely symptomatic. Parenteral volume expansion may counteract the effect of thrombotic process before development of HUS and attenuate renal injury. Use of antibiotics, antimotility agents, narcotics and non-steroidal anti-inflammatory drugs should be avoided during the acute phase. Prevention is best done by preventing primary STEC infection. Underlying aetiology in many cases of aHUS is unknown. A significant number may result from underlying infectious diseases, namely Streptococcus pneumoniae and human immunedeficiency virus. Variety of genetic forms include HUS due to deficiencies of factor H, membrane cofactor protein, Von Willebrand factor-cleaving protease (ADAMTS 13) and intracellular defect in vitamin B12 metabolism. There are cases of aHUS with autosomal recessive and dominant modes of inheritance. Drug-induced aHUS in post-transplantation is due to calcineurin-inhibitors. Systemic lupus erythematosus and catastrophic antiphospholipid syndrome may also present with aHUS. Therapy is directed mainly towards underlying cause.

Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome

Most cases of diarrhoea-associated haemolytic uraemic syndrome (HUS) are caused by Shiga-toxin-producing bacteria; the pathophysiology differs from that of thrombotic thrombocytopenic purpura. Among Shiga-toxin-producing Escherichia coli (STEC), O157:H7 has the strongest association worldwide with HUS. Many different vehicles, in addition to the commonly suspected ground (minced) beef, can transmit this pathogen to people. Antibiotics, antimotility agents, narcotics, and non-steroidal anti-inflammatory drugs should not be given to acutely infected patients, and we advise hospital admission and administration of intravenous fluids. Management of HUS remains supportive; there are no specific therapies to ameliorate the course. The vascular injury leading to HUS is likely to be well under way by the time infected patients seek medical attention for diarrhoea. The best way to prevent HUS is to prevent primary infection with Shiga-toxin-producing bacteria.

Antibody therapy in the management of shiga toxin-induced hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is a disease that can lead to acute renal failure and often to other serious sequelae, including death. The majority of cases are attributed to infections with Escherichia coli, serotype O157:H7 strains in particular, which cause bloody diarrhea and liberate one or two toxins known as Shiga toxins 1 and 2. These toxins are thought to directly be responsible for the manifestations of HUS. Currently, supportive nonspecific treatment is the only available option for the management of individuals presenting with HUS. The benefit of antimicrobial therapy remains uncertain because of several reports which claim that such intervention can in fact exacerbate the syndrome. There have been only a few specific therapies directed against neutralizing the activities of these toxins, but none so far has been shown to be effective. This article reviews the literature on the mechanism of action of these toxins and the clinical manifestations and current management and treatment of HUS. The major focus of the article, however, is the development and rationale for using neutralizing human antibodies to combat this toxin-induced disease. Several groups are currently pursuing this approach with either humanized, chimeric, or human antitoxin antibodies produced in transgenic mice. They are at different phases of development, ranging from preclinical evaluation to human clinical trials. The information available from preclinical studies indicates that neutralizing specific antibodies directed against the A subunit of the toxin can be highly protective. Such antibodies, even when administered well after exposure to bacterial infection and onset of diarrhea, can prevent the occurrence of systemic complications.

Fulminant recurrence of atypical hemolytic uremic syndrome during a calcineurin inhibitor-free immunosuppression regimen

Recurrence of hemolytic uremic syndrome (HUS) after kidney transplantation is frequent, occurring almost exclusively in patients with atypical HUS, which is not caused by Escherichia coli gastroenteritis and in which diarrhea is absent. Calcineurin inhibitors are associated with recurrence of HUS. In two children who underwent living donor kidney transplantation for atypical HUS, we pre-emptively employed sirolimus in a calcineurin inhibitor-free immunosuppression regimen. Both children had excellent early graft function, yet both developed severe recurrent disease and subsequently lost their grafts. Avoidance of calcineurin inhibitors did not prevent recurrence of severe HUS and graft loss. Transplantation for severe atypical HUS remains problematic.

Haemolytic uraemic syndrome

Diarrhoea-associated haemolytic uraemic syndrome develops in about 5 to 10% of children with haemorrhagic colitis due to Escherichia coli (E. coli) O157:H7 and is a common cause of acute renal failure in childhood. Endothelial cell damage, white blood cell activation and platelet-endothelial cell interactions are important in the pathogenesis. Meticulous supportive care, with attention to nutrition and fluid, and electrolyte balance, is important. Dialysis is necessary in many children. Public health follow-up is important to minimise the spread of E. coli O157:H7, which is transmitted by person-to-person, as well as through contaminated food products. 20-year follow-up studies report that 75% of children recover without any clinically significant long term sequelae. Chronic renal failure is reported in about 5% of children.

Thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome

Large and unusually large von Willebrand factor (vWf) multimers may be responsible for systemic platelet aggregation in thrombotic thrombocytopenic purpura (TTP). This possibility is supported by studies that show deficient vWf-cleaving metalloproteinase and increased platelet-vWf binding during TTP episodes. In acute idiopathic TTP, decreased vWf metalloproteinase is the result of autoantibodies against the enzyme. In familial and acquired hemolytic-uremic syndrome, vWf-cleaving metalloproteinase activity is normal. A deficiency or defect in factor H, which normally dampens the activation of C3 via the alternative complement pathway, has been seen in some patients with familial hemolytic-uremic syndrome. Ticlopidine therapy is an important risk factor for TTP.