Classic Hemolytic Uremic Syndrome Research Articles

Thrombotische Mikroangiopathie

Die thrombotische Mikroangiopathie (TMA) zeichnet sich durch eine endothelschadenassoziierte Bildung von Plättchenthromben in arteriellen und venösen Mikrogefäßen aus. Die damit einhergehende Ischämie führt zu schwerwiegenden Organdysfunktionen und kann akut lebensbedrohlich sein. Ätiologisch verbirgt sich hinter der TMA ein sehr heterogenes Erkrankungsspektrum. Neben der thrombotisch-thrombozytopenischen Purpura, die durch eine stark reduzierte ADAMTS13(„a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13“)-Aktivität gekennzeichnet ist, dem infektassoziierten klassischen hämolytisch-urämischen Syndrom (HUS) sowie dem komplementvermittelten atypischen HUS (aHUS) können weitere sehr seltene Erkrankungen oder sekundäre Formen vorliegen. Die differenzialdiagnostische Einteilung ist aufgrund unterschiedlicher therapeutischer Ansätze erforderlich. Der Einsatz neuer spezifischer medikamentöser Behandlungsmethoden hat die Prognose der TMA deutlich verbessert.

A Guide to Differentiating Thrombotic Microangiopathies Through a Case of Catastrophic Antiphospholipid Syndrome

Abstract Thrombotic microangiopathies are rare life-threatening diseases that require prompt diagnosis and treatment to increase patient survival. The prototypical thrombotic microangiopathies are classic hemolytic-uremic syndrome, caused by enterohemorrhagic Escherichia coli, and thrombotic thrombocytopenic purpura. Included in the differential diagnoses and showing overlapping clinical features is antiphospholipid syndrome (APS) and the more severe form, catastrophic APS. Here, we discuss the general approach to thrombotic microangiopathies through a case of APS that later developed into its catastrophic variant.

Atypical hemolytic uremic syndrome and complement blockade: established and emerging uses of complement inhibition.

Atypical hemolytic uremic syndrome (aHUS) is a diagnosis that has captured the interest of specialists across multiple fields. The hallmark features of aHUS are microangiopathic hemolysis and thrombocytopenia, which creates a diagnostic dilemma because of the occurrence of these findings in a wide variety of clinical disorders. In most of the instances, aHUS is a diagnosis of exclusion after ruling out causes such as Shigella toxin, acquired or genetic a disintegrin and metalloproteinase thrombospondin motif 13 deficiency (thrombotic thrombocytopenic purpura), and vitamin B12 deficiency. In the purest sense, aHUS is a genetic condition that is activated (or unmasked) by an environmental exposure. However, it is now evident that complement activation is a feature of many diseases. Variants in complement regulatory genes predispose to microangiopathic hemolysis in many rheumatologic, oncologic, and drug-induced vascular, obstetric, peritransplant, and infectious syndromes. Many 'hemolysis syndromes' overlap clinically with aHUS, and we review the literature on the treatment of these conditions with complement inhibition. New reports on the treatment of C3 glomerulopathy, Shiga toxin-related classic hemolytic uremic syndrome, and medication-related thrombotic microangiopathy will be reviewed as well.

Use of eculizumab in pregnancy-associated atypical hemolytic uremic syndrome

Abstract Pregnancy-associated atypical hemolytic uremic syndrome (p-aHUS) is a rare disorder, with an estimated incidence of 1 in 25,000 pregnancies [Fakhouri F, Roumenina L, Provot F, Sallee M, Caillard S, Couzi L, et al. Pregnancy-associated hemolytic uremic syndrome revisited in the era of complement gene mutations. J Am Soc Nephrol. 2010;21:859–67.]. Unlike classic hemolytic uremic syndrome (HUS), aHUS is not related to Escherichia coli 0157:H7 infections. Rather, it arises from uncontrolled alternative complement pathway activation leading to diffuse endothelial damage. The formation of the resulting fibrin and platelet microthrombi in the vasculature leads to hemolysis, thrombocytopenia and ischemic end-organ damage in the form of acute kidney injury [Noris M, Remuzzi G. Atypical hemolytic-uremic syndrome. N Engl J Med. 2009;361:1676–87; Legendre CM, Licht C, Muus P, Greenbaum LA, Babu S, Bedrosian C, et al. Terminal complement inhibitor eculizumab in atypical hemolytic-uremic syndrome. N Engl J Med. 2013;368:2169–81; Loirat C, Fremeaux-Bacchi V. Atypical hemolytic uremic syndrome. Orphanet J Rare Dis. 2011;6:60; Shen YM. Clinical evaluation of thrombotic microangiopathy: identification of patients with suspected atypical hemolytic uremic syndrome. Thromb J. 2016;14(Suppl 1):19.]. Triggers for hyperactivation of the complement pathway include infection, inflammation, malignancy, endothelium-affecting drugs, maternal-fetal hemorrhage and pre-eclampsia [Shen YM. Clinical evaluation of thrombotic microangiopathy: identification of patients with suspected atypical hemolytic uremic syndrome. Thromb J. 2016;14(Suppl 1):19.]. Thirty percent of individuals with aHUS are found to have mutations in the genes encoding complement regulatory proteins, such as protein factor H, complement factor I and complement 3 [Noris M, Remuzzi G. Atypical hemolytic-uremic syndrome. N Engl J Med. 2009;361:1676–87; Loirat C, Fremeaux-Bacchi V. Atypical hemolytic uremic syndrome. Orphanet J Rare Dis. 2011;6:60.]. Outcomes of an untreated aHUS are poor: up to 50% of patients with aHUS progress to end-stage renal disease within a year and 25% die during the acute phase [Loirat C, Fremeaux-Bacchi V. Atypical hemolytic uremic syndrome. Orphanet J Rare Dis. 2011;6:60; Laurence J, Haller H, Mannucci PM, Nangaku M, Praga M, Rodriguez de Cordoba S. Atypical hemolytic uremic syndrome (aHUS): essential aspects of an accurate diagnosis. Clin Adv Hematol Oncol. 2016;14(Suppl 11):2–15.]. We present an unusual case of a 37-year-old primigravida who developed p-aHUS in the setting of hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome. She was successfully treated with a relatively novel medication; eculizumab, a terminal complement inhibitor. In contrast to previous reports of long-term treatment, she received a total of six doses of eculizumab and remained in remission at 12 months postpartum.

Shiga toxin-producing Escherichia coli (STEC) from Farm Animals and Humans in Tropical Africa - A review

The study was designed to review the incidences and characteristics of Shiga toxin-producing Escherichia coli (STEC) from farm animals and humans in tropical Africa. Serotypes O157, O26, O103, O91, O45 and O111 are usually associated with public health risks, and these serotypes are most frequently isolated from food animals. The main virulent factors of STEC associated with human diseases are potent cytotoxins (shiga toxins [stx] stx1 and stx2), which are encoded by the stx1 and stx2 genes. Two additional markers also play a role in the pathogenesis of Hemorrhagic colitis (HC) and Hemolytic Uremic Syndrome (HUS): an outer membrane protein (intimin), encoded by the eae gene, and enterohaemolysin, encoded by the ehlyA gene. All age groups of animals and humans can be infected with STEC, but young animals and children, the elderly, and those with compromised immune systems are the most severely affected. Little is known about factors that determine susceptibility to STEC infection and the risk factors for the development of systemic complications such as HUS. The peak age incidences (infants and young children) of classical HUS is a reflection of the age incidences of STEC infection as a whole, suggesting that susceptibility to STEC-associated HUS may, like other specific infectious diseases of childhood, be due to the lack of specific immunity, possibly to ST. The increasing recognition of STEC-associated HUS in the elderly would be consistent with waning immunity in that age group. There should be sensitization and awareness regards to the incidences and distribution of STEC serogroups O157, O26, O45, O91, O103 and O111 which are associated with public health risks in livestock and humans in tropical Africa and some parts of the world.

Hemolytic uremic syndrome in children~-- a concise review

The hemolytic uremic syndrome (HUS) is characterized by the triad of thrombocytopenia, micro-angiopathic hemolytic anemia and acute renal failure. This review provides a comprehensive overview of the existing literature on the epidemiology, etiology, pathogenesis, clinical presentation, diagnosi s and management of HUS. The ongoing controversy regarding the role of antibiotics during the acute enteric phase of the classical HUS and the challenges involved in the management of the atypical diseases are highlighted. The most common cause of HUS is systemic uptake of toxins, and develops in 5-10% of children exposed to verocytotoxin-producing Escherichia coli O157:H7. Children below the age of 5 years are the most susceptible hosts and the main route of spread is by fecal-oral transmission. Other infective agents and complement genetic abnormalities are responsible for 10% of cases, referred to as atypical HUS. The characteristic pathologic findings in HUS are renal endoth elial swelling, thrombi in the arterioles and capillaries, and su bendothelial fibrin deposits. After 30 years of discovering Shiga toxins and over 15 years after associating it with the development of HUS, there are neither specific predictive factors to ident ify the most susceptible patients after an infection with E. coli 0157:H7 nor specific treatment for HUS once it has become esta blished. Treatment of HUS is mainly supportive. The introduction of specific toxin neutralizing agents has proven disappointing in clinical practice. Recent trials of E. coli O157:H7 O-specific conjugated polysaccharide vaccines app ear promising in preventing the development of HUS.

Down-Regulation of Renal Klotho Expression by Shiga Toxin 2

Background/Aims: Shiga toxin 2 may trigger classical hemolytic uremic syndrome (HUS) eventually leading to renal failure. Klotho, a transmembrane protein, protease and hormone mainly expressed in kidney is involved in the regulation of renal phosphate excretion and also retains renal protective effects. Renal failure is associated with renal depletion of klotho. The present study explored the influence of Shiga toxin 2 on renal klotho expression. Methods: Mice were injected with either solvent or Shiga toxin 2 and urinary flow rate and phosphate excretion were determined in metabolic cages. Renal transcript levels were measured by quantitative RT-PCR and renal protein abundance by Western blotting. Plasma concentrations of 1,25(OH)₂D₃ and FGF23 were determined by ELISA and plasma phosphate and urea concentrations by photometry. Results: Shiga toxin 2 treatment was followed by increase of plasma urea concentration, urinary flow rate and renal phosphate excretion but not of plasma phosphate concentration. Shiga toxin 2 treatment strongly decreased klotho mRNA expression and klotho protein abundance in renal tissue. Shiga toxin 2 treatment further increased tumor necrosis factor (TnfE) mRNA levels, as well as protein abundance of phosphorylated p38 MAPK in renal tissue. The treatment significantly increased renal Cyp27b1 and decreased renal Cyp24a1 mRNA levels without significantly altering plasma 1,25(OH)₂D₃ levels. Shiga toxin 2 treatment was further followed by increase of plasma FGF23 concentrations. Conclusion: Shiga toxin 2 treatment stimulated TnfE transcription, down-regulated renal klotho expression and increased FGF23 formation, effects presumably contributing to renal tissue injury. i 2015 S. Karger AG, Basel

Invasive Streptococcus Pneumoniae infection Associated with Hemolytic Uremic Syndrome in Chinese Pediatric Patients

Hemolytic uremic syndrome (HUS) associated with pneumococcal pneumonia is rarely reported in the Western literature, in contrast to classical HUS associated with Escherichia coli (E. coli) (O157:H7). We conducted a retrospective review over a 2-year period from 2006 to 2008 in a large tertiary teaching hospital. Five cases were identified. All patients were Chinese children with a median age of 3 years (range: 2 – 4 years). No documented case of E. coli (O157:H7) infection was seen in the same hospital over the past 5 years from 2003 to 2008. Streptococcus pneumoniae (S. pneumoniae) infection was confirmed by positive blood and/or pleural fluid culture. Four of 5 patients developed empyema requiring decortication. HUS was diagnosed as early as 3 days after onset of febrile illness and was apparent within 2 weeks in all patients. The mean nadir for hemoglobin and platelet was 41 g/L (range: 13 – 55 g/L) and 7 ×109/L (range: 4 – 9 ×109/L), respectively. None of them had significant bleeding. All patients received red cell transfusion and 4 of 5 patients received platelet transfusion for prophylaxis or for coverage of invasive procedures. T activation on red cells was documented in all cases. Washed red cells and concentrated pooled platelet-rich plasma were transfused, except for 1 case when transfusion took place before a diagnosis of HUS was made. All patients had impaired renal function as evident by a raised serum creatinine level (range: 101– 756 umol/L). Only 1 patient required dialysis. One patient deteriorated rapidly and died of refractory septicemic shock and multi-organ failure 30 hours after admission. Her hemoglobin and platelet on admission was 106 g/L and 115 ×109/L, respectively. She received unwashed red cells and ordinary platelet concentrate upon clinical deterioration. Blood smear examination and T activation study subsequently confirmed a diagnosis of S. pneumoniae associated HUS. All surviving patients had full renal and hematological recovery with a median follow up of 11 months (range: 3 – 28 months). Invasive S. pneumoniae infection is a relatively common association in Chinese pediatric patients with HUS. This condition can be fatal in the acute state but the medium to long term prognosis is favorable. Transfusion of washed red cells and plasma-reduced platelets is a routine practice in this group of patients, although the efficacy and necessity of this practice has not been formally studied.

Thrombotic microangiopathy in a 17-year-old patient: TTP, HUS or a bit of both?

Thrombotic microangiopathies are characterized by the development of hyaline thrombi in small vessels resulting in thrombocytopenia, microangiopathic hemolysis, and organ dysfunction. Thrombotic-thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are two major clinical syndromes of thrombotic microangiopathies. Although differential diagnosis between TTP and HUS is commonly determined in the clinical setting, recent evidence suggests major pathophysiological differences between the two diseases. Autoimmune inhibitors or genetic mutations of a von Willebrand factor (VWF) cleaving metalloprotease (ADAMTS13) leads to the accumulation of unusually large multimeric forms of VWF in TTP, facilitating adherence of platelets and development of microthrombi. In contrast, classic HUS is caused by infection with verocytotoxin-producing bacteria. This toxin induces endothelial injury, apoptosis and inflammation. Endothelial injury results in increased shear-stress, fostering cleavage of VWF, but thrombosis eventually develops. One would assume that measurement of ADAMTS13 activity and/or detection of verocytotoxin could easily contribute to the differential diagnosis of TTP or HUS. We report on a case of a young patient with thrombotic microangiopathy and renal involvement with low ADAMTS13 concentrations which did not respond well to plasmapheresis therapy, but subsequent to the detection of verocytoxin producing E. coli with the serotype O157:H7, reacted well to antibiotic treatment. Sequencing of the ADAMTS13 gene revealed no mutations and no anti-ADAMTS13 antibodies could be detected. This case shows overlapping presentations as well as etiologies for both TTP and HUS, a finding also underscored by a recent animal model in which verocytoxin triggered development of TTP in ADAMTS13-deficient mice.

Hemolytic uremic syndrome associated withEntamoeba histolytica intestinal infection

Amebiasis secondary to Entamoeba histolytica (E. histolytica) continues to be a major source of morbidity and mortality worldwide, mainly in developing countries. An association between amebic dysentery and hemolytic uremic syndrome (HUS) has been mentioned, but a cause-and-effect relationship has never been confirmed. We report the case of an 11-year-old healthy white female who developed severe bloody diarrhea after drinking contaminated unboiled water, developing classic HUS and requiring acute intermittent hemodialysis. The etiological study confirmed numerous cysts and hematophagous trophozoites of E. histolytica on stool smear, but without evidence of other pathogens. This report contributes to the concept that classic post-diarrheal HUS, usually related to colitis secondary to enterohemorragic Shiga-toxin producing Escherichia coli (E.coli) strains, may be associated with other pathogens, including E. histolytica. Additional information regarding mechanisms of virulence of E. histolytica and host immunological reaction is needed to clarify the temporal association of these two disorders (HUS and amebiasis).

Lipopolysaccharide Upregulates Renal Shiga Toxin Receptors in a Primate Model of Hemolytic Uremic Syndrome

Background: Although Shiga toxin (Stx) mediates classical hemolytic uremic syndrome (HUS), it is not fully understood why only some subjects exposed to Stx-expressing Escherichia coli develop HUS. We have previously shown in a baboon model of Stx-mediated HUS that coadministration of lipopolysaccharide (LPS) results in an augmented host response to otherwise subtoxic Stx1 doses. We used this model to test the hypothesis that LPS upregulates renal Stx receptor (Gb₃) expression. Methods: Juvenile baboons were treated with either Stx1 (100 ng/kg), LPS (1 mg/kg as two divided doses 24 h apart), or a sham injection of saline, and sacrificed and immediately autopsied at 72 h. Renal cortical tissue Gb₃ content was quantitated by lipid extraction and thin-layer chromatography, and Stx1 and Gb₃/CD77 immunostaining was assessed by quantitative immunofluorescent microscopy. Results: Compared to saline-in jected controls, LPS administration resulted in a 2.2-fold increase in renal cortical Gb₃ by chromatography (p < 0.01), a 2.5-fold increase in Stx1 staining (p = 0.003) and a 1.7-fold increase in CD77 immunostaining (p = 0.004). Stx treatment did not significantly alter either Stx or CD77 immunostaining. Conclusion: These observations suggest that LPS primes the host for Stx-mediated renal injury by upregulating renal Gb₃ expression.

The “cutting” edge: von Willebrand factor-cleaving protease activity in thrombotic microangiopathies

The thrombotic microangiopathies (TMAs), including thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), are classically defined by constellations of clinical findings. In the late 1990’s, several groups reported that a single test might be able to diagnose TTP and distinguish it from HUS. This test was an assay to detect von Willebrand factor-cleaving protease activity. Although there has been debate in the literature as to the utility of this assay, review of the available data suggests that this test can separate the idiopathic TMAs into three distinct categories: (1) patients who are protease positive with severe renal failure (similar to classic HUS), (2) patients who are protease positive without severe renal failure and (3) patients who are protease negative. While the latter two categories may appear similar to TTP at presentation, the prognosis differs in each of these groups of patients. Through use of the protease assay clinicians will be better able to diagnose, treat, predict outcome and design clinical trials.

Recurrence of hemolytic uremic syndrome after renal transplantation in children: a report of the North American Pediatric Renal Transplant Cooperative Study.

Hemolytic uremic syndrome (HUS) is the cause of renal failure in 2-4% of children on dialysis. After renal transplantation, HUS can recur, but recurrence rate and risk factors are controversial. We reviewed the recurrence of HUS within the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) registry and used a separate questionnaire to ascertain additional clinical information. Of 68 renal allografts, HUS recurred in 6 allografts (8.8%) occurring in five patients (8.2%). Four patients had atypical HUS, whereas one patient had classic HUS. HUS recurred after transplantation in 33 days or less in all but one allograft. Outcome was poor with five of six allografts lost, despite treatment with fresh-frozen plasma or plasmapheresis. Cyclosporine had no effect on outcome or HUS recurrence. The risk of HUS recurrence in the allograft is 8-9% and is heightened in atypical HUS. Treatment was not effective and graft outcome was poor. Cyclosporine does not affect HUS recurrence.

Usefulness of serum fibrinogen degradation product-E in sporadic cases of classical hemolytic uremic syndrome.

Hemolytic uremic syndrome (HUS) associated with Shiga toxin (Stx)-producing Escherichia coli O157:H7 infection is one of the diseases causing acute renal failure in young children. Although HUS is still a serious disease in children, no reliable predictive markers for HUS nor markers of disease severity are available so far. Recently, we experienced a sporadic case of typical HUS caused by Stx-producing E. coli O157:H7 and detected, at the prodromal stage, a high level of serum fibrin/fibrinogen degradation product-E (FDP-E) fraction. To assess the usefulness of FDP-E for the treatment of HUS in clinical practice, we retrospectively examined serum levels of FDP-E in 22 patients with bloody diarrhea with or without HUS. There were significantly increased levels of serum FDP-E in patients with HUS, but not in those without HUS. Furthermore, serum levels of FDP-E may correlate with disease severity in patients with HUS. These results suggest that serum levels of FDP-E may be a useful marker of HUS in clinical practice.

Circulating inflammatory cytokine levels in hemolytic uremic syndrome.

Experimental data suggest that the host's inflammatory response is involved in the pathophysiology of verotoxin-producing Escherichia coli (VTEC)-associated hemolytic uremic syndrome (HUS). We compared the circulating levels of pro- [interleukin (IL)-6, IL-8] and anti-inflammatory [IL-10 and IL-1 receptor antagonist (Ra)] mediators on enrollment among children with HUS due to E. coli O157:H7, according to the severity of renal dysfunction. The latter was evaluated by the occurrence of oligoanuria, the requirement for dialysis, and a glomerular filtration rate (GFR) </=80 ml/min per 1. 73 m(2) measured 1 year later. Increased levels of IL-6 (P<0.0001), IL-10 (P<0.0001), and IL-1Ra (P<0.07) were found among patients with HUS compared with normal controls. Children with severe renal dysfunction also had tenfold increased levels of IL-6 and higher concentrations of IL-10 and IL-1Ra. Both the IL-6/IL-10 (4.9+/-8.3 vs. 0.5+/-0.4, P=0.01) and the IL-6/IL-1Ra ratios (0.10+/-0.20 vs. 0. 01+/-0.01, P=0.04) were significantly increased. GFR correlated well with IL-6 levels, IL-6/IL-10 and IL-6/IL-1Ra ratios. Our data demonstrate that the inflammatory response of the host is associated with the severity of renal dysfunction during classic HUS. An imbalance between the pro- and the anti-inflammatory responses may be involved in the pathophysiology of VTEC-associated HUS.

Atteinte cardiaque au cours du syndrome hémolytique et urémique typique

Cardiac involvement rarely occurs in classic hemolytic uremic syndrome (HUS); it is often fatal. The first patient, a 21-month-old boy, developed classic HUS with acute renal failure. Peritoneal dialysis was performed for 20 days. On the 10th day of dialysis, myocardial infarction occurred, probably related to coronary thrombus. The patient was given heparin and antibiotics because of an unexplained fever. The outcome was favorable despite antero-apical cardiac necrosis, and moderated chronic renal failure. The second patient, a 24-month-old girl, also showed a classic HUS, which required peritoneal dialysis for 10 days. Dilated cardiomyopathy with cardiac failure appeared on the 4th day of dialysis, not related to the volume overload and metabolic consequences of the acute renal failure, such as systemic hypertension or ineffective dialysis. On the 5th day of dialysis neurological involvement appeared. Neurological, cardiac and renal outcome was favorable. The third patient, a 25-month-old girl, developed a classical HUS, requiring peritoneal dialysis for 25 days. No cardiac insult appeared during the acute phase of the disease. After dialysis, the child had chronic renal failure (creatinine clearance: 15 mL/min/1.73 m2). Dilated cardiomyopathy appeared 3 months later, without definite etiology. The outcome was favorable with digoxin treatment. A cardiac involvement should also be searched for in the acute phase of HUS and several months later.

Inflammatory mediators in Escherichia coli O157:H7 hemorrhagic colitis and hemolytic-uremic syndrome.

Recent experimental data suggest that the inflammatory response of the host to verotoxin and/or lipopolysaccharides of Escherichia coli is involved in the pathophysiology of verotoxin-producing E. coli (VTEC) infections. We measured the circulating concentrations of cytokines [TNF-alpha, interleukin (IL)-1-beta, IL-1 receptor antagonist (Ra), IL-6, IL-8, IL-10] and soluble leukocyte adhesion molecules (L-selectin, P-selectin, E-selectin, intracellular cell adhesion molecule-1, vascular cell adhesion molecule-1) by sandwich enzyme-linked immunosorbent assay among (1) normal controls (n = 12), (2) disease controls with hemorrhagic colitis (HC) not associated with VTEC infections (n = 57), (3) patients with uncomplicated HC caused by E. coli O157:H7 (n = 30), and (4) children with hemolytic-uremic syndrome (HUS) (n = 28). Patients with HUS were matched with children who presented an uncomplicated HC caused by E. coli O157:H7 for the time interval elapsed between the onset of HC and that of blood sample collection. Concentrations of TNF-alpha and IL-1-beta were undetectable. Children with HUS were characterized by increased amounts of IL-6 and IL-8, lower values of soluble L-selectin as well as increased levels of IL-10 and IL-1Ra. The circulating concentrations of IL-1Ra were higher among children with O157:H7 HC who subsequently developed HUS. Increased pro- and antiinflammatory cytokine responses are produced by the host during the development of HUS among children with VTEC infections. Further studies are needed to determine their relative contribution to the pathophysiology of classic HUS.

Novel Role of bFGF in the Pathogenesis of Classic Hemolytic Uremic Syndrome(HUS). † 1681

Novel Role of bFGF in the Pathogenesis of Classic Hemolytic Uremic Syndrome(HUS). † 1681

Isolation of enterohemorrhagic Escherichia coli O157 strains from patients with hemolytic-uremic syndrome by using immunomagnetic separation, DNA-based methods, and direct culture.

We examined 30 children with classical hemolytic-uremic syndrome (HUS) for the presence of enterohemorrhagic Escherichia coli (EHEC) strains in stool samples and determined the specific immune response to O157 lipopolysaccharide in acute-phase serum samples from these patients. EHEC O157 strains were isolated from stool samples of 18 (60%) of the patients, and non-O157 EHEC strains were isolated from 5 (17%) of the patients. For O157 strain isolation from stools, we introduced a selective enrichment step using O157-specific antibodies attached to paramagnetic particles (immunomagnetic separation [IMS] method). This procedure allowed the detection of O157 strains at 10(2) CFU/g of stool in the presence of 10(7) coliform background flora organisms. By using IMS followed by plating on sorbitol MacConkey (SMAC) agar and cefixime-tellurite SMAC (CT-SMAC) agar, O157 strains were detected in 18 samples, whereas colony hybridization detected a subset of 12 positive samples and direct culture on CT-SMAC or SMAC agar detected only 7. Three of the 18 O157-positive stools were negative by cytotoxicity assay performed with stool filtrates and by direct PCR with DNA extracted from stools. The IMS technique allowed the isolation of O157 strains from 18 of 20 patients with serological evidence for O157 infection. Apart from the increase in sensitivity in O157 detection compared with that of direct culture, the IMS technique also has the advantage of being less labor-intensive and less time-consuming than the molecular methods. IMS can therefore be considered an efficient method for wide-spread use in the detection of O157 strains in clinical microbiology laboratories. However, because a significant number of HUS cases were attributable to non-O157 EHEC serogroups, the use of additional methods besides IMS in the bacteriological diagnosis of HUS is necessary.

Immune Response to Verotoxin 1 and 2 in Children withEscherichia ColiO157:H7 Hemorrhagic Colitis and Classic Hemolytic Uremic Syndrome

To compare neutralizing antibody titres against verotoxin (vt)-1 and vt-2 between children with uncomplicated hemorrhagic colitis (hc) and those with classic hemolytic uremic syndrome (hus). vt antibody titres were also compared in children with hc who received trimethoprim-sulfamethoxazole with those who did not. Prospective study. Tertiary pediatric hospital. Children with hc (n=41) or classic hus (n=12). Serum antibodies against vt-1 and vt-2 were determined by quantitative neutralization. Antibodies were detected in 40% (21 of 53) of serum samples for vt-1 and in 100% (53 of 53) of samples for vt-2. A positive immune response, defined as a fourfold increase in vt antibody titres or as a single titre of 1/64 or greater, was found in 0% (0 of 12) of patients with hus compared with 7% (three of 41) of those with hc for vt-1 (P=0.4); and in 17% (two of 12) of patients with hus compared with 22% (nine of 41) of those with hc for vt-2 (P=0.3). The rate of seroconversion against either vt-1 or vt-2 was comparable in treated and untreated patients with uncomplicated hc. There was no evidence that neutralizing antibody levels against vt-1 or vt-2 in classic hus or after antibiotic therapy are substantially different from those in patients with uncomplicated hc.