THE HEMOLYTIC-UREMIC SYNDROME

Effect of Shiga toxins on granulocyte function

We already showed that injection of Shiga toxin (Stx) 2 into mice caused severe granulocytosis in the peripheral blood. In this study we further clarified changes of granulocyte function by Stx 2. The activity of medullasin, a neutral serine protease in granulocytes that injures endothelial cells in vessels, significantly increased when Stx 2 was injected into mice intraperitoneally. Since granulocyte count in the peripheral blood of mice was markedly increased after intraperitoneal injection of Stx 2, medullasin activity in the peripheral blood was remarkably elevated. In contrast to Stx 2, injection of Stx 1 into mice caused no elevation of medullasin activity in granulocytes nor increase in granulocyte count in the peripheral blood. Cathepsin G levels in granulocytes increased only slightly after Stx 2 injection. Granulocytes obtained from mice injected with Stx 2 showed reduced superoxide-producing activity compared with those from controls. Addition of Stx 2 or Stx 1 to human mature granulocytes in vitro decreased their superoxide-producing activity when stimulated with agonists. Therefore, these toxins produced from Escherichia coli augment toxic effect of the bacteria by reducing bactericidal activity of granulocytes. Tissue injury in organisms infected with Shiga toxin-producing E. coli is mainly derived from elevated neutral proteases, such as medullasin, in granulocytes rather than direct toxic effect of superoxide from granulocytes. Hemolytic uremic syndrome caused by Shiga toxin-producing E. coli infection is due, at least in part, to the elevation of medullasin levels produced by granulocytes.

Up-regulation of Duffy antigen receptor expression in children with renal disease

BACKGROUND

The Duffy antigen chemokine receptor (DARC) is a promiscuous chemokine receptor that binds chemokines from the C-X-C and C-C families. DARC was initially described on red blood cells, but subsequent studies have demonstrated DARC protein expression on renal endothelial and epithelial cells, even in Duffy-negative individuals whose red cells lack DARC. Because approximately 68% of African Americans lack the Duffy/DARC on their red cells, we carried out experiments to identify the specific renal cells expressing DARC protein and mRNA in African American children and to define whether DARC expression was altered in renal inflammatory processes.

METHODS

Immunohistochemistry and in situ hybridization studies were done in 28 renal sections from children with each of the following diagnoses: HIV nephropathy (HIVAN), HIV-associated hemolytic uremic syndrome (HIV-HUS), HIV infection without renal disease, HIV-negative children without renal disease, and Argentinean children with classic HUS.

RESULTS

The predominant localization of DARC mRNA and protein was found in endothelial cells underlying postcapillary renal venules in all patients studied. However, DARC mRNA and protein were significantly up-regulated in peritubular and glomerular capillaries, collecting duct epithelial cells, and interstitial inflammatory cells in children with HIVAN, HIV-HUS, and classic HUS.

CONCLUSION

These findings support the notion that the renal DARC is linked to the inflammatory cascade and that African American children may be at risk of accumulating chemokines in renal tissues.

Neuropsychological sequelae of haemolytic uraemic syndrome. Investigators of the HUS Cognitive Study

BACKGROUND

Severe haemolytic uraemic syndrome (HUS) in childhood can cause stroke, hemiplegia, cortical blindness, and psychomotor retardation. These outcomes are evident at the time of discharge immediately after the acute illness. Less is known about the neuropsychological outcomes of less severely affected children who recover from acute HUS.

AIMS

This multicentre case control study investigated the hypothesis that children who survive an acute episode of HUS without recognizable neurological injuries have greater impairment of cognitive, academic, and behavioural functions than controls.

DESIGN

Children with HUS were eligible if they had no evidence of severe neurological dysfunction when discharged from one of six Canadian hospitals. Controls had been admitted to hospital for a non-HUS illness and were matched by age, sex, first language, and socioeconomic status. All subjects underwent evaluation of behaviour, academic achievement, cognitive function, and verbal abilities using standardised tests administered by a psychometrist blinded to the case or control status.

RESULTS

Ninety-one case control pairs were enrolled. No important differences between patients with HUS and paired controls were evident on tests of IQ, behaviour, verbal abilities, or academic achievement. There was no increased risk of attention deficit disorder among patients with HUS. There was no correlation between the severity of acute renal failure and neuropsychological measures, although scores on some verbal ability tests were lower in those with the highest serum creatinine concentrations during illness.

CONCLUSIONS

Children discharged from hospital without apparent neurological injury after an episode of acute HUS do not have an increased risk of subclinical problems with learning, behaviour, or attention.

Hemolytic uremic syndrome in children: platelet aggregation and membrane glycoproteins

PURPOSE

Several mechanisms have been proposed to explain the fibrin-platelet thrombosis at the microcirculation level in the different clinical conditions of hemolytic uremic syndrome (HUS). The relationships between platelet structure and function during the first 4 weeks of evolution of the disease were studied to understand the mechanism of platelet alteration.

PATIENTS AND METHODS

Coagulation parameters, platelet counts, and aggregation were studied in 49 children, and membrane glycoproteins (GPs) in 20 of the 49 children (mean age, 17 months) with HUS (Group 2) were studied during the first 4 weeks of evolution of the disease.

RESULTS

No disseminated intravascular coagulation was found in patients with recurrent or persistent thrombocytopenia. Platelet aggregation was sequentially performed during the first weeks of evolution. All patients had a functional decrease in the acute period of HUS. Platelet GPs GPIb, GPIIbIIIa, GPIIb, and GPIIIa were evaluated. GPIIbIIIa complex presented low level and never reached normal values during the first 4 weeks of disease.

CONCLUSIONS

Platelet alterations are probably caused by multiple mechanisms: "exhausted" platelets, structural membrane alterations caused by arginine-glycine-aspartic peptide blockade, or diminished or nonfunctional membrane GPIb and GPIIbIIIa complexes.

Recruitment of renal tubular epithelial cells expressing verotoxin-1 (Stx1) receptors in HIV-1 transgenic mice with renal disease

BACKGROUND

Human immunodeficiency virus (HIV)-infected children are at risk of developing several renal parenchymal diseases, including hemolytic uremic syndrome (HUS). HUS is most frequently caused by infection with enteric Escherichia coli producing Shiga-like toxins (Stxs). In vitro studies have shown that cytokines known to be present at high systemic levels in HIV-1-infected children up-regulate the expression of the Stx glycolipid receptor (Gb3) in cultured endothelial cells. Thus, we studied whether HIV-1 or the HIV-associated "cytokine milieu" could modulate the expression of renal Stxs receptors in vivo.

METHODS

We used HIV-1 transgenic mice (HIV-Tg) expressing a deletion mutant of HIV-1 (pNL4-3). These mice develop renal disease similar to that of HIV-1-infected children. The expression of Gb3 was studied in renal sections from control and HIV-Tg mice by histochemistry, thin layer chromatography overlay studies, and high-pressure liquid chromatography.

RESULTS

By histochemistry, we found a significant recruitment of renal tubular epithelial cells expressing Gb3 in HIV-Tg mice with nephropathy, whereas kidneys from control mice showed limited staining in renal tubules. Gb3 was not found in glomeruli of either control or HIV-Tg mice. Thin layer chromatography overlay studies with Stxs and high-pressure liquid chromatography studies confirmed the marked elevation of Gb3 in HIV-Tg kidneys with renal disease.

CONCLUSIONS

These results suggest that the presence of HIV-associated nephropathy is associated with the recruitment of renal tubular epithelial cells expressing Stx1 receptors. The up-regulation of Stx1 receptors in HIV-diseased kidneys may increase the sensitivity of these cells to the cytotoxic effects of Stxs.

Escherichia coli O157:H7

Escherichia coli O157 was first identified as a human pathogen in 1982. One of several Shiga toxin-producing serotypes known to cause human illness, the organism probably evolved through horizontal acquisition of genes for Shiga toxins and other virulence factors. E. coli O157 is found regularly in the faeces of healthy cattle, and is transmitted to humans through contaminated food, water, and direct contact with infected people or animals. Human infection is associated with a wide range of clinical illness, including asymptomatic shedding, non-bloody diarrhoea, haemorrhagic colitis, haemolytic uraemic syndrome, and death. Since laboratory practices vary, physicians need to know whether laboratories in their area routinely test for E. coli O157 in stool specimens. Treatment with antimicrobial agents remains controversial: some studies suggest that treatment may precipitate haemolytic uraemic syndrome, and other studies suggest no effect or even a protective effect. Physicians can help to prevent E. coli O157 infections by counselling patients about the hazards of consuming undercooked ground meat or unpasteurised milk products and juices, and about the importance of handwashing to prevent the spread of diarrhoeal illness, and by informing public-health authorities when they see unusual numbers of cases of bloody diarrhoea or haemolytic uraemic syndrome.

Hemolytic uremic syndrome - clinical aspects and outcome of an outbreak: Report of 28 cases

Hemolytic uremic syndrome (HUS) is characterized by microangiopathic hemolytic anemia, thrombocytopenia and acute renal failure. There are two main subgroups: the typical form of HUS follows a diarrheal prodrome (D+HUS) and the atypical form is without the diarrheal prodrome (D-HUS). We have studied 28 children with HUS over a period of 15 months between 1992 and 1993. The median age was 2.2 years (range from six months to six years). All children had prodromal diarrhea. Hypertension was present in 71% and neurological complications in 39%. All the patients had oliguria or anuria (16 oliguric and 12 anuric). The mean duration of anuria was 16 days (range seven to 42 days). Serum creatinine on admission ranged between 112 and 1064 Amicromol/L (mean 453 Amicromol/L). The lowest hemoglobin level and platelet count during hospitalization ranged between 38 and 87 g/L and 7 to 147x109/L respectively. Leukocytosis on admission was present in 22 patients, low C3 was documented in 11 patients (34%), and four patients had low C4. All patients received fresh frozen plasma transfusion, a total of 25 patients received dialysis therapy, 19 patients were treated with peritoneal dialysis (PD), one patient had hemodialysis (HD), and five patients had both HD and PD. The mean duration of dialysis was 18 days (range three to 56 days). Only one patient died (mortality rate 3%). The median duration of hospital stay was 28 days (range eight to 90 days). We conclude that HUS is emerging as an important clinical and public health problem and that early comprehensive management including dialysis therapy, aggressive management of hypertension, fresh frozen plasma transfusion, and nutritional support all improve the outcome and decrease the mortality and morbidity in patients with HUS.

Extrarenal involvement in diarrhoea-associated haemolytic-uraemic syndrome

A review of extrarenal involvement in diarrhoea-associated haemolytic-uraemic syndrome (HUS) is based on 64 of our autopsied patients and an update of the literature. Large bowel pathology was the commonest (29 cases), followed by the central nervous system (21 cases), the heart (19 cases) and the pancreas (19 cases). The severity of systemic involvement was associated with the magnitude of renal compromise and the prognosis of the acute phase. Diarrhoea-associated HUS is described as a multiorgan entity, due to extensive microvascular damage and thrombosis. At present mortality during the acute phase is not confined to renal failure; systemic involvement can also lead to death.

Microbiology of fresh and restructured lamb meat: a review

Microbiology of meats has been a subject of great concern in food science and public health in recent years. Although many articles have been devoted to the microbiology of beef, pork, and poultry meats, much less has been written about microbiology of lamb meat and even less on restructured lamb meat. This article presents data on microbiology and shelf-life of fresh lamb meat; restructured meat products, restructured lamb meat products, bacteriology of restructured meat products, and important foodborne pathogens such as Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in meats and lamb meats. Also, the potential use of sodium and potassium lactates to control foodborne pathogens in meats and restructured lamb meat is reviewed This article should be of interest to all meat scientists, food scientists, and public health microbiologists who are concerned with the safety of meats in general and lamb meat in particular.

Racial incidence of hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children and is caused by infection with verotoxin-producing Escherichia coli. There is no consensus on the relative incidence of HUS in blacks and whites. An equal racial incidence has been reported by two centers with small black populations. A series from Washington D.C. reported a low incidence in blacks. The population of Alabama is 32% black and 66% white. The Children's Hospital of Alabama admission rate has a similar racial distribution (35% black, 65% white). A record review from 1980-1992 identified 45 patients with HUS; 43 (96%) were white and only 2 (4%) were black. Based on census data for Alabama in 1980 and 1990, this gives an average annual incidence of HUS of 0.45 per 100,000 in whites and of 0.043 per 100,000 in blacks (P < 0.001, Fischer's exact test). Similar results were found in the group of patients with HUS and a history of diarrhea; whites 0.39 and blacks 0.02 (P < 0.001). However, in those with no history of diarrhea there was no significant racial difference: whites 0.05 and blacks 0.02. There were too few blacks to compare clinical course and outcome. We conclude that typical diarrhea-associated HUS is a relatively rare disease in blacks compared with whites. The reasons are unclear.

Escherichia coli O 157:H7-associated hemolytic-uremic syndrome after ingestion of contaminated hamburgers

We conducted a retrospective analysis of 37 children with Escherichia coli O157:H7-associated hemolytic-uremic syndrome. The infection was traced to contaminated hamburgers at a fast-food restaurant chain. Within 5 days of the first confirmed case, the Washington State Department of Health identified the source and interrupted transmission of infection. Ninety-five percent of the children initially had severe hemorrhagic colitis. Nineteen patients (51%) had significant extrarenal abnormalities, including pancreatitis, colonic necrosis, glucose intolerance, coma, stroke, seizures, myocardial dysfunction, pericardial effusions, adult respiratory disease syndrome, and pleural effusions. Three deaths occurred, each in children with severe multisystem disease. At follow-up two children have significant impairment of renal function (glomerular filtration rate < 80 ml/min/per 1.73 Hm2); both of these children have a normal serum creatinine concentration. Hemolytic-uremic syndrome is the most common cause of acute renal failure in children, and this experience emphasizes the systemic nature of this disease. Clinicians should anticipate that multisystem involvement may occur in these patients, necessitating acute intervention or chronic follow-up. This outbreak of Hemolytic-uremic syndrome also highlights the microbiologic hazards of inadequately prepared food and emphasizes the importance of public health intervention in controlling Hemolytic-uremic syndrome.

Evidence that verotoxins (Shiga-like toxins) from Escherichia coli bind to P blood group antigens of human erythrocytes in vitro

The interaction of verotoxins (VTs) with human erythrocytes (RBCs) in vitro was investigated, with particular reference to the role of P blood group glycolipids that are structurally related to the known VT receptors. RBC binding of purified VT1, VT2, VT2c, and VT2e was detected by direct and indirect immunofluorescence. Glycolipids were extracted from defined RBCs, separated by thin-layer chromatography, and assessed for VT binding in an overlay assay by adding toxin and specific antibodies. All VTs bound to P1 phenotype (Pk, P, and P1 antigens) and P2 phenotype (Pk and P antigens) RBCs but not to p phenotype (lacking the Pk, P, and P1 antigens) RBCs. Binding of VT1 and VT2 was approximately 10-fold greater to P1 and the rare Pk2 (Pk antigen but no P1 or P antigen) phenotype cells than to P2 phenotype RBCs, whereas VT2e bound equally well to P1 and P2 phenotype cells. The VT1 and VT2 immunofluorescence results correlated with the detection of P1 and/or increased amounts of Pk (globotriaosylceramide) antigen; VT2e immunofluorescence correlated with the detection of P (globotetraosylceramide) antigen. The Pk band pattern and VT binding observed in the thin-layer chromatogram of human P1 and P phenotype RBC extracts varied from that of human kidney and Pk1 phenotype (Pk and P1 antigens) RBCs. We conclude that each VT binds to human RBCs in vitro by utilizing specific P blood group glycolipids as receptors. On P1 and P phenotype RBCs, the accessibility of the Pk antigen for VTs appeared to be restricted. The occurrence of VT-RBC binding in natural VT-producing Escherichia coli disease and its relevance for the pathophysiology of hemolytic uremic syndrome remain to be established.

Stimulation of gastrointestinal antibody to Shiga toxin by orogastric immunization in mice

Shiga toxin (ST) is a protein toxin of Shigella dysenteriae type 1, a causative agent of severe diarrhoea and dysentery. In this report we describe the gastrointestinal secretory antibody response of mice following orogastric immunization with ST. Gastrointestinal secretions were sampled by a gastrointestinal lavage technique weekly for 5 weeks after initial immunization. Assay of lavage samples by ELISA showed that mice vaccinated orogastrically with various doses of ST developed gastrointestinal antibody to ST in a dose-dependent manner. Serum anti-ST activity developed by 5 weeks after initial immunization. The ability of ST to act as a mucosal immune adjuvant was investigated by coadministration of ST and keyhole limpet haemocyanin. In contrast to cholera toxin, a potent adjuvant, ST did not demonstrate adjuvant activity. The mouse gastrointestinal lavage model could be useful for further analysis of the cellular basis of ST immunogenicity.

Hypoproteinemia in the hemolytic-uremic syndrome of childhood

A retrospective review of admission serum protein concentration in 18 children with hemolytic-uremic syndrome (HUS) showed significantly decreased serum total protein, albumin and globulin concentrations upon admission compared with 22 matched controls (P < 0.003). One child with atypical disease without diarrhea had normal serum protein concentrations. A strongly positive correlation (P = 0.006) was found between the age of HUS patients with diarrhea and their lowest total protein concentrations. In 10 children who eventually required hemodialysis, there was a significantly negative correlation (r = -0.8316, P = 0.01) between the admission serum albumin and the patients' highest creatinine levels, suggesting that hypoproteinemia may be a risk factor in the development of renal failure. The pathophysiological and clinical significance of hypoproteinemia in HUS needs further investigation.

Hemolytic-uremic syndrome

HUS is one of the most common causes of acute renal failure in childhood. D+ HUS is the most common form and usually follows an episode of hemorrhagic colitis due to VTEC or S. dysenteriae type 1. The SLT elaborated by these organisms is responsible for the endothelial damage that is the initial insult in the pathogenesis of the acute renal failure. Excellent supportive care is necessary to reduce the mortality and morbidity due to HUS.

Enterohemorrhagic Escherichia coli associated with hemolytic-uremic syndrome in Chilean children

A clinicoepidemiological study was undertaken to determine if enterohemorrhagic Escherichia coli (EHEC) was associated with hemolytic-uremic syndrome (HUS) in children in Santiago, Valdivia, and Temuco, Chile. Prospective surveillance detected 20 hospitalized cases of HUS in children less than 4 years of age in these cities from March 1988 to March 1989. Each HUS patient was matched (by sex and age) with two control children (hospitalized elective-surgery patients). To detect EHEC, DNA from stool culture isolates of E. coli was detected by hybridization with biotin-labelled DNA probes specific for the EHEC virulence plasmid, Shiga-like toxin I (SLT-I) or SLT-II. Stool cultures from 6 of 20 cases (30%) and from 2 of 38 controls (5.3%) yielded EHEC (P = 0.0158). EHEC isolates from all HUS cases hybridized with the EHEC plasmid probe and with probes for SLT-I or -II (or both). The serogroups of the isolates included O157, O26, and O111. EHEC causes HUS in Chile, and the biotinylated gene probes are practical diagnostic tools for epidemiologic studies.

Sequelae of haemolytic uraemic syndrome

Twenty two patients with previous episodes of haemolytic uraemic syndrome (HUS) were investigated for evidence of deficits in cognitive, behavioural, and academic function. Patients were pair matched with 22 controls for age (+/- 1 year), gender, and socioeconomic status. HUS patients had numerically lower cognitive and achievement scores and higher behavioural problem ratings than their controls on every measure. None of the group differences was significant at the 0.01 level. Significance values between 0.10 and 0.01 were obtained for the Wechsler full scale and verbal intelligence quotient scores and for several of the achievement measures and behaviour ratings. These results were conservatively interpreted as trends and are considered to provide preliminary indications of a post-HUS deficit in behaviour, verbal intelligence, and the verbally based skills of reading comprehension and vocabulary. The findings provide interim guidelines for follow up care but require confirmation and elaboration in a larger study.

Shiga toxin-associated hemolytic uremic syndrome: combined cytotoxic effects of shiga toxin and lipopolysaccharide (endotoxin) on human vascular endothelial cells in vitro

This study explores the in vitro relationship between Shiga toxin-producing Shigella spp. and Escherichia coli and the development of vascular complications in humans following bacillary dysentery. We propose that lipopolysaccharide (LPS; endotoxin) may combine with Shiga toxin to facilitate vascular damage characteristic of hemolytic uremic syndrome. We have examined the direct cytotoxic effects of Shiga toxin and LPS on human umbilical vein endothelial cells (HUVEC) in culture. Shiga toxin alone was cytotoxic to HUVEC, whereas LPS was noncytotoxic at concentrations at or below 10 micrograms/ml. Combinations of LPS with Shiga toxin resulted in a synergistic cytotoxic effect. The synergistic cytotoxic response of HUVEC to Shiga toxin plus LPS was dose dependent for both agents and was maximal at 24 h of exposure. This synergistic response was enhanced by preincubation of HUVEC with LPS. LPS (1 micrograms/ml) alone depressed HUVEC protein synthesis in a transient manner and enhanced the protein synthesis-inhibiting activity of Shiga toxin. The synergistic cytotoxic activity of LPS analogs was as follows, in decreasing order: complete LPS = diphosphoryl lipid A greater than monophosphoryl lipid A greater than deacylated LPS. These results are consistent with a role for Shiga toxin and LPS in the development of hemolytic uremic syndrome at the level of the vascular endothelium in humans.

Neutrophil activation in the haemolytic uraemic syndrome: free and complexed elastase in plasma

There is evidence of neutrophil involvement in the pathogenesis of the haemolytic uraemic syndrome (HUS), and neutrophil release products are thought to cause endothelial cell damage. Elastase is the major lysosomal proteinase liberated by activated neutrophils. In this study we measured both free and complexed elastase. No free elastase activity could be detected in the plasma of patients with diarrhoea-associated (D+) HUS using a specific substrate. However, there was a marked increase in alpha 1-antitrypsin (alpha 1-AT) complexed elastase as measured by a newly developed enzyme-linked immunosorbent assay not only in D+ HUS, but also in non-diarrhoea-associated (D-) HUS. This finding is independent of either a high polymorphonuclear leucocyte count or renal failure. This increase in bound elastase together with our sequential data which demonstrate raised alpha 1-AT complexed elastase levels early in the disease process further support the theory that neutrophil activation is one of the key events in the pathophysiology of this disorder.

Shiga toxin-associated hemolytic-uremic syndrome: combined cytotoxic effects of Shiga toxin, interleukin-1 beta, and tumor necrosis factor alpha on human vascular endothelial cells in vitro

This study explores the relationship between Shiga toxin-producing Shigella or Escherichia coli strains and the development of vascular complications in humans following bacillary dysentery. We propose that endotoxin-elicited interleukin-1 or tumor necrosis factor alpha (TNF) may combine with Shiga toxin to facilitate vascular damage characteristic of hemolytic-uremic syndrome. This study examines the cytotoxic effects of Shiga toxin, interleukin-1, and TNF on cultured human umbilical vein endothelial cells (HUVEC). Both Shiga toxin and TNF were cytotoxic to HUVEC, although HUVEC obtained from individual umbilical cords differed in their sensitivities to these agents. With Shiga toxin-sensitive HUVEC, combinations of TNF with Shiga toxin resulted in a synergistic cytotoxic effect. In contrast, interleukin-1 was not cytotoxic to HUVEC, nor did it enhance cell death in combination with Shiga toxin. The synergistic cytotoxic response of HUVEC to Shiga toxin and TNF was dose and time dependent for both agents and could be neutralized by monoclonal antibodies directed against either Shiga toxin or TNF. This synergistic response was delayed, being maximal on day 2. Preincubation (24 h) of HUVEC with TNF sensitized the cells to Shiga toxin. TNF alone had no effect on HUVEC protein synthesis but enhanced the inhibitory activity of Shiga toxin. These results are consistent with a role for Shiga toxin in the development of hemolytic-uremic syndrome at the level of the vascular endothelium in humans.

Prostacyclin concentrations in haemolytic uraemic syndrome after acute shigellosis in children

The role of prostacyclin in the pathogenesis of haemolytic uraemic syndrome was evaluated in 11 children with acute shigellosis. Plasma concentrations of 6-keto prostaglandin, F1 alpha, a stable metabolite of prostacyclin, were measured by radioimmunoassay during acute illness, early convalescence, and after clinical recovery. Its concentration was low during acute illness in each patient, returning to normal concentrations or above at the time of the last sample. These results suggest that plasma prostacyclin may be involved in the development of the syndrome.

Renal transplantation in patients with classical haemolytic-uraemic syndrome

Eighteen records from children with renal transplants (RT) and classical haemolytic-uraemic syndrome (HUS) were reviewed. The mean oliguric period was 17.9 +/- 7.5 days; the interval between acute phase and end-stage renal disease (ESRD) was 9.3 +/- 5.2 years. HUS was the most frequent cause of renal transplantation (23.4%). There were no significant differences between patients with HUS and controls (children with RT but without HUS), regarding renal function, frequency of rejections, renal survival (HUS 65%, controls 57%) or patient survival (94.4% and 96.6%, respectively) after 9 years. None had clinical or histopathological evidence of HUS recurrence in the allograft. Of all children with living-related donors (LRD), renal survival after 3 years was longer for those who received cyclosporin A (CSA) (HUS and controls 86%) than for those who did not receive it (HUS 50%, controls 53%). Classical HUS is a frequent cause of ESRD in Argentina. The duration of the acute oliguric period is a good predictor of the likelihood of progression to chronicity. In the classical form of HUS there is no recurrence in the allograft. CSA and LRD can be used without risk in renal transplantation of children with classical HUS.

Haemolytic anaemia after childhood Escherichia coli O 157 .H7 infection: are females at increased risk?

We conducted a 4-year retrospective cohort study to better define the risk of haemolytic anaemia and haemolytic uraemic syndrome (HUS) in children following sporadic gastrointestinal infection with the O 157.H7 serotype of Escherichia coli. Of the 72 children infected with this organism, 9 (12.5%) developed haemolytic anaemia, 6 of whom had HUS. No child in a cohort of 72 age-matched controls with Campylobacter jejuni gastroenteritis developed haemolytic anaemia (P = 0.003). Females had a significantly greater risk of developing haemolytic anaemia after E. coli O 157. H7 infection than did males (8/29 females v. 1/43 males; P = 0.003). In a logistic regression model, female gender emerged as the only statistically significant risk factor for haemolytic anaemia (odds ratio 3.85; 95% confidence interval 1.24-12). These results are consistent with recent reports of a moderate increase in the risk of HUS for females.

The epidemiology and clinical aspects of the hemolytic uremic syndrome in Minnesota

BACKGROUND

The frequency of the hemolytic uremic syndrome, characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure, is increasing. Although Escherichia coli serotype O157:H7 has been implicated as a causative agent, more information is needed about the basic epidemiology and clinical aspects of this syndrome.

METHODS

We conducted a retrospective population-based study of hemolytic uremic syndrome in Minnesota residents less than 18 years of age from 1979 through 1988 to assess trends in disease occurrence, describe the clinical illness, and identify predictors of disease severity and outcome. We also conducted a case-control study of patients with onsets of illness from 1986 through 1988 to examine risk factors.

RESULTS

One hundred seventeen patients were identified. The mean annual incidence increased from 0.5 case per 100,000 child-years among children less than 18 in 1979 (6 cases) to 2.0 cases per 100,000 in 1988 (26 cases) (P = 0.000004). E. coli O157:H7 was isolated from 13 of 28 patients (46 percent) who had stool specimens submitted for testing. For those who presented with typical hemolytic uremic syndrome, an elevated polymorphonuclear-leukocyte count on hospital admission, a shorter duration of prodrome, and the presence of bloody diarrhea were predictive of severe disease. In the case-control study, the patients were more likely to attend large daycare centers (more than 50 children) than were the controls (odds ratio, 10.2; P = 0.03), suggesting that day-care attendance may be a risk factor. On the basis of the population-attributable risk, however, this factor could account for no more than 16 percent of the cases.

CONCLUSIONS

This study provides evidence for an increase in the incidence of hemolytic uremic syndrome, which is probably related to an increased incidence of E. coli O157:H7 infections. Hemolytic uremic syndrome has become an important pediatric and public health problem.

Renal functional reserve compared in haemolytic uraemic syndrome and single kidney

Creatinine clearance and microalbuminuria were measured before and after an oral protein load in 17 children with a history of haemolytic uraemic syndrome, 11 with a single kidney, and 15 controls, all of them normotensive and without evidence of renal damage, to look for indirect evidence of glomerular hyperfiltration. While creatinine clearance increased significantly after the protein load in controls, it did not change in patients with either haemolytic uraemic syndrome or a single kidney. Basal microalbuminuria was significantly higher in those with haemolytic uraemic syndrome when compared with those with a single kidney and controls. It increased significantly in all groups after a water load; this increase was significantly higher in haemolytic uraemic syndrome. After the protein load microalbuminuria returned to baseline. In conclusion, children with a history of haemolytic uraemic syndrome have an abnormal renal functional reserve like children with a single kidney. Only patients with haemolytic uraemic syndrome exhibited an increased microalbuminuria, however, suggesting that it may be the expression of a pathophysiological mechanism involved in haemolytic uraemic syndrome and not in single kidney, that could account for their different prognosis.

Increased thromboxane biosynthesis in childhood hemolytic uremic syndrome

Vascular endothelial cell damage plays a central role in the pathogenesis of the hemolytic uremic syndrome (HUS), resulting in intravascular platelet activation and thrombotic microangiopathy. A deficiency of the antiaggregatory prostacyclin (PGI2) has been postulated by experiments under ex vivo conditions. However, this observation has not been confirmed in vivo. The pathophysiological contribution of thromboxane (Tx)A2, a potent vasoconstrictor and platelet-aggregating prostanoid which is predominantly produced by platelets, has not been elucidated so far. In order to quantitate endogenous formation of TxA2 in children with HUS, plasma concentrations of the enzymatic metabolite 11-dehydro-TxB2 of TxA2 and urinary excretion rates of three major TxA2 metabolites, TxB2, 11-dehydro-TxB2 and 2,3-dinor-TxB2 were analyzed using gas chromatography/mass spectrometry. PGI2 biosynthesis was assessed by measuring urinary excretion of an index metabolite of its systemic production, 2,3-dinor-6-keto-prostaglandin (PG) F1 alpha, and an index of its renal production, 6-keto-PGF1 alpha. TxA2 biosynthesis was markedly elevated in the acute phase of HUS. This activation could be detected for a longer period of time than the presence of thrombocytopenia. Concomitantly in the acute phase, renal PGI2 formation was significantly elevated and systemic PGI2 formation was elevated in 50% of the patients. These data indicate that TxA2 formation is increased in the acute phase in patients with HUS. This enhanced biosynthesis is consistent with increased platelet activation, whereas the increased PGI2 biosynthesis reflects predominantly renal endothelial cell damage.

Neutrophil-mediated endothelial injury in haemolytic uraemic syndrome

Neutrophil leucocytosis is associated with a poor outcome in the haemolytic uraemic syndrome (HUS). This study tested the hypothesis that neutrophils from HUS patients are activated and through release of their intracellular contents damage endothelium. The proportion of neutrophils adhering to endothelium in culture was twice as high for HUS patients' neutrophils as for control neutrophils (n = 12). In addition, these neutrophils induced endothelial injury, assessed morphologically by degradation of endothelial cell fibronectin. In an attempt to inhibit neutrophil adhesion and subsequent endothelial damage the hyperadhesive neutrophils from HUS patients were incubated with a CD18 antibody directed against the common beta chain of the leucocyte integrin molecules. The CD18 antibody was able to abrogate endothelial damage in four of the ten subjects studied. These observations suggest that the neutrophil is of prime pathophysiological importance in HUS, and that methods aimed at reducing neutrophil adhesion and neutrophil-mediated endothelial damage are likely to be beneficial.

Infection by verocytotoxin-producing Escherichia coli

Verocytotoxin (VT)-producing Escherichia coli (VTEC) are a newly recognized group of enteric pathogens which are increasingly being recognized as common causes of diarrhea in some geographic settings. Outbreak studies indicate that most patients with VTEC infection develop mild uncomplicated diarrhea. However, a significant risk of two serious and potentially life-threatening complications, hemorrhagic colitis and the hemolytic uremic syndrome, makes VTEC infection a public health problem of serious concern. The main reservoirs of VTEC appear to be the intestinal tracts of animals, and foods of animal (especially bovine) origin are probably the principal sources for human infection. The term VT refers to a family of subunit exotoxins with high biological activity. Individual VTEC strains elaborate one or both of at least two serologically distinct, bacteriophage-mediated VTs (VT1 and VT2) which are closely related to Shiga toxin and are thus also referred to as Shiga-like toxins. The holotoxins bind to cells, via their B subunits, to a specific receptor which is probably the glycolipid, globotriosyl ceramide (Gb3). Binding is followed by internalization of the A subunit, which, after it is proteolytically nicked and reduced to the A1 fragment, inhibits protein synthesis in mammalian cells by inactivating 60S ribosomal subunits through selective structural modification of 28S ribosomal ribonucleic acid. The mechanism of VTEC diarrhea is still controversial, and the relative roles of locally acting VT and "attaching and effacing adherence" of VTEC to the mucosa have yet to be resolved. There is increasing evidence that hemolytic uremic syndrome and possibly hemorrhagic colitis result from the systemic action of VT on vascular endothelial cells. The role of antitoxic immunity in preventing the systemic complications of VTEC infection is being explored. Antibiotics appear to be contraindicated in the treatment of VTEC infection. The most common VTEC serotype associated with human disease is O157:H7, but over 50 different VT-positive O:H serotypes have now been identified. The best strategies for diagnosing human VTEC infection include testing for the presence of free VT in fecal filtrates and examining fecal cultures for VTEC by means of deoxyribonucleic acid probes that specify genes encoding VT1 and VT2. Both methods are currently confined to specialized laboratories and await commercial development for wider use. In the meantime, most laboratories should continue to screen for the most common human VTEC serotype, O157:H7, using a sorbitol-containing MacConkey medium.

Role of Shiga toxin in the pathogenesis of bacillary dysentery, studied by using a Tox- mutant of Shigella dysenteriae 1

A Tox- mutant of Shigella dysenteriae 1, SC501, was genetically engineered by cloning the Shiga toxin operon, inserting a cassette into the A subunit gene, and exchanging this in vitro-mutagenized sequence with the wild-type gene. SC501 produced a low amount of residual cytotoxicity which was not neutralized by a rabbit immune serum directed against Shiga toxin. Invasion of cultured cells demonstrated that Shiga toxin had no effect on the rate of intracellular growth of bacteria or on the rapid killing of invaded host cells. On the other hand, several significant differences were observed in macaque monkeys infected intragastrically with either the wild-type strain or its mutant. The production of Shiga toxin by the invading strain was correlated with the presence of blood within stools, a sharp drop in blood polymorphonuclear cells, and histopathological alterations, such as the destruction of capillary vessels within the connective tissue of the colonic mucosa, severe inflammatory vasculitis of the peritoneal mesothelium, and major efflux of inflammatory cells to the intestinal lumen. It is proposed that Shiga toxin influences the severity of bacillary dysentery by inducing colonic vascular damage, which accounts for bloody stools, intestinal ischemia, and inflation of a polymorphonuclear intestinal compartment during the infectious process.

A family outbreak of hemolytic-uremic syndrome associated with verotoxin-producing Escherichia coli serotype O157:H7

All five siblings (three boys and two girls, aged 1.5-9 years) in a family developed hemolytic-uremic syndrome associated with verotoxin-producing Escherichia coli O157:H7 at a lakeside vacation cottage during the fall of 1985. All five were hospitalized and made a full recovery. Both parents remained asymptomatic, and neither had evidence of this infection. In four children who were investigated prospectively, free verotoxin was still detectable in the stools for between 3 and 7 weeks. The prodromal diarrheal illness in the children occurred over a 10-day period. The epidemic curve was consistent with a point-source outbreak, but continuous exposure or person-to-person transmission could not be ruled out. The source of the infection was not identified.

Direct cytotoxic action of Shiga toxin on human vascular endothelial cells

To help explain a role of the Shiga toxin family in hemorrhagic colitis and hemolytic-uremic syndrome in humans, it has been hypothesized that these toxins cause direct damage to the vascular endothelium. We now report that Shiga toxin purified from Shigella dysenteriae 1 does indeed have a direct cytotoxic effect on vascular endothelial cells in cultures. Human umbilical vein endothelial cells (HUVEC) in confluent monolayers were reduced 50% by 10(-8) M Shiga toxin after a lag period of 48 to 96 h. In comparison, nonconfluent HUVEC were reduced 50% by 10(-10) M Shiga toxin within a 24-h period. These data suggest that dividing endothelial cells are more sensitive to Shiga toxin than are quiescent cells in confluent monolayers. Both confluent and nonconfluent HUVEC specifically bound 125I-Shiga toxin. However, in response to the toxin, rates of incorporation of [3H]leucine into protein were more severely reduced in nonconfluent cells than in confluent cells. Toxin inhibition of protein synthesis preceded detachment of cells from the substratum. The specific binding of 125I-Shiga toxin to human endothelial cells and the cytotoxic response were both toxin dose dependent and neutralized by anti-Shiga toxin antibody. Heat-denatured Shiga toxin was without the cytotoxic effect. In addition, the complete culture system contained less than 0.1 ng of bacterial endotoxin per ml, as measured by the Limulus amoebocyte lysate test.

Haemolytic uraemic syndrome associated with faecal cytotoxin and verotoxin neutralizing antibodies

Forty-nine patients with a diagnosis of idiopathic haemolytic uraemic syndrome (HUS) were investigated to determine evidence of infection by verotoxin-producing Escherichia coli (VTEC). Free faecal cytotoxin active on Vero cells (VT) was detected in 15 out of 49 patients (31%). Seroconversion or high titres of VT-neutralizing antibodies were detected in 11 out of 18 patients (61%). The results of the present study suggest an association between HUS and infection by VTEC.

Cytotoxin-producing Escherichia coli and the hemolytic uremic syndrome

Recently, a new class of diarrhea-associated Escherichia coli has been linked to the hemolytic uremic syndrome. The organisms included in this group produce cell-damaging toxins (cytotoxins) related to Shigatoxin made by S. dysenteriae 1. The most common pathogen in this group is E. coli O157:H7.

Intravascular platelet activation in the hemolytic uremic syndrome

We studied intravascular platelet activation in patients with typical (epidemic) and atypical (sporadic) HUS and found defective aggregation, decreased platelet and increased plasma serotonin in both groups. The findings were present not only on admission during the thrombocytopenic stage of the disease, but persisted for several weeks after recovery of the platelet count. Reduced endothelial PGI2 production was significantly more common in plasma from atypical than typical cases. Plasma from both typical and atypical HUS patients induced aggregation of normal platelets, but this phenomenon was unrelated to both the presence of thrombocytopenia or the stage of the disease. Serum platelet aggregating activity was higher in the atypical HUS patients, and was not associated with immune complexes detectable by polyethylene glycol precipitation. The data indicate that intravascular platelet activation is a feature of both forms of HUS, and may be initiated by different mechanisms in the two subgroups. While abnormal PGI2 synthesis appears to be important in the atypical cases, neither defective PGI2 production nor platelet aggregation by plasma factors adequately accounts for platelet activation in the majority of typical cases.

Lacunar infarction of the basal ganglia as a complication of hemolytic-uremic syndrome. MRI and clinical correlations

Central nervous system (CNS) complications of hemolytic-uremic syndrome (HUS) commonly consist of alterations in mental status, seizures, and rarely hemiparesis. The authors report the clinical evolution of left hemiparesis and later choreo-athetoid movements in a patient who sustained a right lacunar infarction as a complication of HUS. The infarction is demonstrated on magnetic resonance imaging (MRI).

Necrosis of the pancreas in the haemolytic uraemic syndrome

A case of haemolytic uraemic syndrome in a three year old boy is described. The clinical course was complicated by hyperglycaemia, and biochemical assay of plasma showed an almost total lack of pancreatic insulin. Extensive necrosis of the exocrine and endocrine pancreas was found at necropsy. The possible pathological physiology of this complication and its prognostic importance are discussed.

Haemolytic-uraemic syndrome: an analysis of prognostic features

Seventy-two children with the haemolytic-uraemic syndrome were seen between 1969 and 1980 at The Hospital for Sick Children and Guy's Hospital, London. They probably constitute the majority of such cases in south-east England during that period. Boys and girls were affected equally, the mean age at presentation was 3.5 years, and a peak incidence of the disorder in summer months was observed. In 52 (72%) there was a history of diarrhoea at onset. Fifty-seven (78%) were managed by dialysis. Fifty (70%) of the 72 children had a favourable outcome with complete recovery, 3 (4%) died in the acute phase of the illness, 8 (11%) had residual hypertension or chronic renal failure, and 11 (16%) never recovered renal function. The probability of complete recovery of renal function was analysed by logistic regression which indicated that younger age, presentation in the summer months, diarrhoea at onset and, in those patients who were dialysed, a short prodromal illness were associated with a good outcome. Further analysis of the interaction among these variables in the patient group as a whole indicated that diarrhoea favoured a good outcome among boys but not girls.

Comparative immunopathologic studies of thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome and disseminated intravascular coagulation

The vascular lesion of thrombotic thrombocytopenic purpura was characterized by two distinct types of changes in the arteriole of the heart and brain: (1) multiple incomplete vascular occlusions due to the subendothelial deposits composed of a homogeneous fibrin fibrinogen-like substance and platelets without the formation of polymerized fibrin; (2) vascular wall thickening due to the intramural granular deposits of IGM and beta 1C. A patient with hemolytic-uremic syndrome 9 days after the onset of the disease, exhibited (1) the formation of fibrin-thrombi in the glomerular capillary lumens, and (2) the granular deposits of IgM and beta 1C along the glomerular capillary walls and in the mesangium. In contrast, the case in which the symptoms subsided five weeks after the onset exhibited neither fibrin-thrombus formation nor the deposits of IgM and beta 1C in the glomeruli. The vascular lesions of disseminated intravascular coagulation accompanied by pancreas carcinoma was located mainly in the capillaries, and were characterized by the formation of numerous fibrin-thrombi. Although the glomeruli contained numerous thrombi, there was neither endocapillary proliferation nor deposits of immunoglobulins and complement components.

Hemolytic-uremic syndrome: a diagnostic and therapeutic dilemma for the surgeon

The hemolytic-uremic syndrome consists of microangiopathic hemolytic anemia, acute renal failure, and thrombocytopenia following a prodromal illness of gastroenteritis or upper respiratory infection. The syndrome can present in dramatic fashion with severe abdominal pain and signs of peritonitis suggesting an acute surgical crisis. In a series of 25 patients, 40% had abdominal pain, 25% had abdominal tenderness, and 20% had peritoneal signs. Clues to diagnosis in the early stages of the acute illness were mild to moderate hypertension, abnormal peripheral blood smear, anemia despite dehydration, and proteinuria. Significant abdominal pain and x-ray evidence of colitis may occur before development of typical laboratory findings, and these were evident in at least one case. Three patients underwent laparotomy for suspected bowel perforation. Colitis without perforation was found in all cases. In the absence of documented perforation, toxic megacolon, or intussusception, the decision to perform laparotomy in patients with hemolytic-uremic syndrome who have signs of peritonitis must be individualized. Failure to recognize the underlying renal problem can lead to serious errors in fluid and electrolyte management and delay of appropriate therapy.

Lipid peroxidation in the hemolytic uremic syndrome

Based on recent evidence of a genetic influence on prognosis (1) and the existence of red cell membrane phospholipid depletion with low or absent serum alpha-tocopherol (2) levels in three children with the Hemolytic Uremic Syndrome (H.U.S.), we wish to suggest the existence of an inborn error of antioxident capacity as the basic pathogenetic mechanism in the development of the hemolytic uremic syndrome (H.U.S.).