Cytotoxin-producing Escherichia coli and the hemolytic uremic syndrome

Plasma membrane profiling during enterohemorrhagic E. coli infection reveals that the metalloprotease StcE cleaves CD55 from host epithelial surfaces

Enterohemorrhagic Escherichia coli (EHEC) is one of several E. coli pathotypes that infect the intestinal tract and cause disease. Formation of the characteristic attaching and effacing lesion on the surface of infected cells causes significant remodeling of the host cell surface; however, limited information is available about changes at the protein level. Here we employed plasma membrane profiling, a quantitative cell-surface proteomics technique, to identify host proteins whose cell-surface levels are altered during infection. Using this method, we quantified more than 1100 proteins, 280 of which showed altered cell-surface levels after exposure to EHEC. 22 host proteins were significantly reduced on the surface of infected epithelial cells. These included both known and unknown targets of EHEC infection. The complement decay–accelerating factor cluster of differentiation 55 (CD55) exhibited the greatest reduction in cell-surface levels during infection. We showed by flow cytometry and Western blot analysis that CD55 is cleaved from the cell surface by the EHEC-specific protease StcE and found that StcE-mediated CD55 cleavage results in increased neutrophil adhesion to the apical surface of intestinal epithelial cells. This suggests that StcE alters host epithelial surfaces to depress neutrophil transepithelial migration during infection. This work is the first report of the global manipulation of the epithelial cell surface by a bacterial pathogen and illustrates the power of quantitative cell-surface proteomics in uncovering critical aspects of bacterial infection biology.

Ultralarge von Willebrand factor-induced platelet clumping and activation of the alternative complement pathway in thrombotic thrombocytopenic purpura and the hemolytic-uremic syndromes

The molecular linkage between ultralarge (UL) von Willebrand factor (VWF) multimers and the alternative complement pathway (AP) has recently been described. Endothelial cell (EC)-secreted and anchored ULVWF multimers (in long stringlike structures) function as both hyperadhesive sites that initiate platelet adhesion and aggregation and activating surfaces for the AP. In vitro, the active form of C3, C3b binds to the EC-anchored ULVWF multimeric strings and initiates the assembly on the strings of C3 convertase (C3bBb) and C5 convertase (C3bBbC3b). In vivo, activation of the AP via this mechanism proceeds all the way to generation of terminal complement complexes (C5b-9).

Escherichia coli O157:H7 bacteriophage Φ241 isolated from an industrial cucumber fermentation at high acidity and salinity

A novel phage, Φ241, specific for Escherichia coli O157:H7 was isolated from an industrial cucumber fermentation where both acidity (pH ≤ 3.7) and salinity (≥5% NaCl) were high. The phage belongs to the Myoviridae family. Its latent period was 15 min and average burst size was 53 phage particles per infected cell. The phage was able to lyse 48 E. coli O157:H7 strains, but none of the 18 non-O157 strains (including E. coli O104:H7) or the 2 O antigen-negative mutants of O157:H7 strain, 43895Δper (also lacking H7 antigen) and F12 (still expressing H7 antigen). However, the phage was able to lyse a per-complemented strain (43895ΔperComp) which expresses O157 antigen. These results indicated that phage Φ241 is specific for O157 antigen, and E. coli strains lacking O157 antigen were resistant to the phage infection, regardless of the presence or absence of H7 antigen. SDS-PAGE profile revealed at least 13 structural proteins of the phage. The phage DNA was resistant to many commonly used restriction endonucleases, suggesting the presence of modified nucleotides in the phage genome. At the multiplicity of infection of 10, 3, or 0.3, the phage caused a rapid cell lysis within 1 or 2 h, resulting in 3.5- or 4.5-log-unit reduction in cell concentration. The high lytic activity, specificity and tolerance to low pH and high salinity make phage Φ241 a potentially ideal biocontrol agent of E. coli O157:H7 in various foods. To our knowledge, this is the first report on E. coli O157:H7 phage isolated from high acidity and salinity environment.

Interaction of Shiga toxin with the A-domains and multimers of von Willebrand Factor

Shiga toxin (Stx) produced by enterohemorrhagic Escherichia coli causes diarrhea-associated hemolytic-uremic syndrome (DHUS), a severe renal thrombotic microangiopathy. We investigated the interaction between Stx and von Willebrand Factor (VWF), a multimeric plasma glycoprotein that mediates platelet adhesion, activation, and aggregation. Stx bound to ultra-large VWF (ULVWF) secreted from and anchored to stimulated human umbilical vein endothelial cells, as well as to immobilized VWF-rich human umbilical vein endothelial cell supernatant. This Stx binding was localized to the A1 and A2 domain of VWF monomeric subunits and reduced the rate of ADAMTS-13-mediated cleavage of the Tyr(1605)-Met(1606) peptide bond in the A2 domain. Stx-VWF interaction and the associated delay in ADAMTS-13-mediated cleavage of VWF may contribute to the pathophysiology of DHUS.

GLOBAL DYNAMICS OF A DIFFERENTIAL SUSCEPTIBILITY MODEL

An SIS epidemiological model in a population of varying size with two dissimilar groups of susceptible individuals has been analyzed. We prove that all the solutions tend to the equilibria of the system. Then we use the Poincaré Index theorem to determine the number of the rest points and their stability properties. It has been shown that bistability occurs for suitable values of the involved parameters. We use the perturbations of the pitchfork bifurcation points to give examples of all possible dynamics of the system. Some numerical examples of bistability and hysteresis behavior of the system has been also provided.

Thrombotic microangiopathy in systemic lupus erythematosus: a cohort study in North Taiwan

OBJECTIVES

Thrombotic microangiopathy (TMA) co-existing with SLE is rarely reported. This study aimed to investigate the triggering factors, clinical features and outcomes of SLE patients with TMA in Northern Taiwan.

METHODS

Twenty-five TMA cases out of 2461 SLE patients admitted to Taipei Veterans General Hospital, between 2000 and 2010, were enrolled.

RESULTS

When TMA occurred, 16 (64.0%) patients had infection; 22 (88.0%) were in an active disease state with a SLEDAI score >10. Among the infection group, 13 (81.3%) had an increase in the SLEDAI score of ≥ 4. We found that older age (≥ 50 years), low platelets (≤ 20,000/nm(3)), presence of infection, acute renal failure (ARF) or four or more TMA features were independent risk factors for persistent haematological abnormalities (P < 0.05); older age (≥ 50 years) and a high reticulocyte index (>2%) were the risk factors for persistent renal function impairment (P < 0.05). The overall mortality rate was 52.0% (13 out of 25); older age (≥ 40 years), low complement value, presence of infection (P < 0.001), two or more infection sources, ARF and four or more TMA features were the statistically significant factors contributing to a higher mortality rate. Patients receiving plasma exchange seven times or more had a significantly higher rate of improvement in renal function and haematological abnormalities.

CONCLUSIONS

Our study showed that infection was one of the major triggers for the flare-up of SLE disease activity and occurrence of TMA in SLE. Infection is also a strong risk factor for outcome in SLE patients with TMA. Plasma exchange can be considered as an adjuvant treatment modality.

Pathogenesis of thrombotic microangiopathies

Profound thrombocytopenia and microangiopathic hemolytic anemia characterize thrombotic microangiopathy, which includes two major disorders: thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). TTP has at least three types: congenital or familial, idiopathic, and nonidiopathic. The congenital and idiopathic TTP syndromes are caused primarily by deficiency of ADAMTS13, owing to mutations in the ADAMTS13 gene or autoantibodies that inhibit ADAMTS13 activity. HUS is similar to TTP, but is associated with acute renal failure. Diarrhea-associated HUS accounts for more than 90% of cases and is usually caused by infection with Shiga-toxin-producing Escherichia coli (O157:H7). Diarrhea-negative HUS is associated with complement dysregulation in up to 50% of cases, caused by mutations in complement factor H, membrane cofactor protein, factor I or factor B, or by autoantibodies against factor H. The incomplete penetrance of mutations in either ADAMTS13 or complement regulatory genes suggests that precipitating events or triggers may be required to cause thrombotic microangiopathy in many patients.

Systematic review: are antibiotics detrimental or beneficial for the treatment of patients with Escherichia coli O157:H7 infection?

BACKGROUND

Escherichia coli O157:H7 is a foodborne pathogen causing haemorrhagic colitis, which is sometimes complicated by haemolytic uraemic syndrome or thrombotic thrombocytopenic purpura.

AIM

To review the available evidence regarding the question of whether antibiotics are effective or harmful for the treatment of patients infected with E. coli O157:H7 infection.

METHODS

We searched in the PubMed for relevant laboratory and clinical studies published between 1982 and 2005.

RESULTS

In vitro studies have shown that most E. coli O157:H7 isolates are susceptible to various antibiotics, although certain antibiotics, especially at sublethal concentrations, have been found to increase the release of Shiga-like toxins, which have been associated with the development of haemolytic uraemic syndrome/thrombotic thrombocytopenic purpura in humans. No clinical studies have indicated that antibiotics are effective in reducing the duration of E. coli O157:H7 infection or the duration of diarrhoea or bloody diarrhoea specifically, while a few studies have supported that some antibiotics, especially quinolones and fosfomycin, may prevent the development of haemolytic uraemic syndrome or thrombotic thrombocytopenic purpura. On the other hand, there are some clinical studies that associate antibiotics with a higher risk for haemolytic uraemic syndrome and/or longer duration of diarrhoea, even with high mortality.

CONCLUSIONS

More randomized controlled trials are necessary in order to elucidate whether antibiotics are effective in reducing the morbidity and mortality of E. coli O157:H7 infection, rather than having a detrimental effect.

Predictors of fatality in postdiarrheal hemolytic uremic syndrome

OBJECTIVES

Describe the cause of deaths among patients with postdiarrheal hemolytic uremic syndrome (HUS) and identify predictors of death at the time of hospital admission.

METHODS

Case-control study of 17 deaths among patients with HUS identified from the Intermountain HUS Patient Registry (1970-2003) compared against all nonfatal cases.

RESULTS

Of the 17 total deaths, 15 died during the acute phase of disease. Two died because treatment was withdrawn based on their preexisting conditions, and 1 died because of iatrogenic cardiac tamponade; they were excluded from analysis. Brain involvement was the most common cause of death (8 of 12); congestive heart failure, pulmonary hemorrhage, and hyperkalemia were infrequent causes. Presence of prodromal lethargy, oligoanuria, or seizures and white blood cell count (WBC) >20 x 10(9)/L or hematocrit >23% on admission were predictive of death. In multivariate analysis, elevated WBC and elevated hematocrit were independent predictors. The combination of prodromal dehydration, oliguria, and lethargy and admission WBC values >20 x 10(9)/L and hematocrit >23% appeared in 7 of the 12 acute-phase deaths.

CONCLUSIONS

Diarrheal HUS patients presenting with oligoanuria, dehydration, WBC >20 x 10(9)/L, and hematocrit >23% are at substantial risk for fatal hemolytic uremic syndrome. Such individuals should be referred to pediatric tertiary care centers.

Hemolytic uremic syndrome-associated Shiga toxins promote endothelial-cell secretion and impair ADAMTS13 cleavage of unusually large von Willebrand factor multimers

Shiga toxin 1 (Stx-1) and Stx-2 produced by enterohemorrhagic Escherichia coli cause the diarrhea-associated hemolytic uremic syndrome (HUS). This type of HUS is characterized by obstruction of the glomeruli and renal microvasculature by platelet-fibrin thrombi, acute renal failure, thrombocytopenia, microvascular hemolytic anemia, and plasma levels of von Willebrand factor (VWF)-cleaving protease (ADAMTS13) activity that are within a broad normal range. We investigated the mechanism of initial platelet accumulation on Stx-stimulated endothelial cells. Stx-1 or Stx-2 (1-10 nM) stimulated the rapid secretion of unusually large (UL) VWF multimeric strings from human umbilical vein endothelial cells (HUVECs) or human glomerular microvascular endothelial cells (GMVECs). Perfused normal human platelets immediately adhered to the secreted ULVWF multimeric strings. Nanomolar concentrations (1-10 nM) of the Shiga toxins were as effective in inducing the formation of ULVWF-platelet strings as millimolar concentrations (0.1-20 mM) of histamine. The rate of ULVWF-platelet string cleavage by plasma or recombinant ADAMTS13 was delayed by 3 to 10 minutes (or longer) in the presence of 10 nM Stx-1 or Stx-2 compared with 20 mM histamine. Stx-induced formation of ULVWF strings, and impairment of ULVWF-platelet string cleavage by ADAMTS13, may promote initial platelet adhesion above glomerular endothelial cells. These processes may contribute to the evolution of glomerular occlusion by platelet and fibrin thrombi in diarrhea-associated HUS.

Differential susceptibility epidemic models

We formulate compartmental differential susceptibility (DS) susceptible-infective-removed (SIR) models by dividing the susceptible population into multiple subgroups according to the susceptibility of individuals in each group. We analyze the impact of disease-induced mortality in the situations where the number of contacts per individual is either constant or proportional to the total population. We derive an explicit formula for the reproductive number of infection for each model by investigating the local stability of the infection-free equilibrium. We further prove that the infection-free equilibrium of each model is globally asymptotically stable by qualitative analysis of the dynamics of the model system and by utilizing an appropriately chosen Liapunov function. We show that if the reproductive number is greater than one, then there exists a unique endemic equilibrium for all of the DS models studied in this paper. We prove that the endemic equilibrium is locally asymptotically stable for the models with no disease-induced mortality and the models with contact numbers proportional to the total population. We also provide sufficient conditions for the stability of the endemic equilibrium for other situations. We briefly discuss applications of the DS models to optimal vaccine strategies and the connections between the DS models and predator-prey models with multiple prey populations or host-parasitic interaction models with multiple hosts are also given.

Acid resistance systems required for survival of Escherichia coli O157:H7 in the bovine gastrointestinal tract and in apple cider are different

Escherichia coli O157:H7 is a highly acid-resistant food-borne pathogen that survives in the bovine and human gastrointestinal tracts and in acidic foods such as apple cider. This property is thought to contribute to the low infectious dose of the organism. Three acid resistance (AR) systems are expressed in stationary-phase cells. AR system 1 is sigma(S) dependent, while AR systems 2 and 3 are glutamate and arginine dependent, respectively. In this study, we sought to determine which AR systems are important for survival in acidic foods and which are required for survival in the bovine intestinal tract. Wild-type and mutant E. coli O157:H7 strains deficient in AR system 1, 2, or 3 were challenged with apple cider and inoculated into calves. Wild-type cells, adapted at pH 5.5 in the absence of glucose (AR system 1 induced), survived well in apple cider. Conversely, the mutant deficient in AR system 1, shown previously to survive poorly in calves, was susceptible to apple cider (pH 3.5), and this sensitivity was shown to be caused by low pH. Interestingly, the AR system 2-deficient mutant survived in apple cider at high levels, but its shedding from calves was significantly decreased compared to that of wild-type cells. AR system 3-deficient cells survived well in both apple cider and calves. Taken together, these results indicate that E. coli O157:H7 utilizes different acid resistance systems based on the type of acidic environment encountered.

Hemolytic uremic syndrome in an adolescent with Fusobacterium necrophorum bacteremia

Microorganisms may produce substances that disrupt the interaction between platelets and vascular endothelium, which has been associated with atypical hemolytic uremic syndrome (HUS). We present the first reported case of Fusobacterium necrophorum bacteremia that presented initially with atypical HUS. Antimicrobial therapy eradicated the patient's bacteremia, and plasmapheresis restored platelet-endothelial homeostasis. Understanding the pathophysiologic mechanisms involved in atypical HUS would guide the development of more precise therapies.

Relationship between susceptibility to hemolytic-uremic syndrome and levels of globotriaosylceramide in human sera

The relationship between differential susceptibility to hemolytic-uremic syndrome (HUS) and levels of globotriaosylceramide (Gb3) in serum was studied in patients infected with verotoxin-producing Escherichia coli (VTEC). The serum Gb3 levels in patients with HUS were lower than these in diarrheal patients without subsequent HUS or in patients without clinical symptoms, indicating that individuals with a lower content of serum Gb3 show a higher incidence of HUS following VTEC infection.

Infarction of the choledochus, liver, gallbladder, and pancreas: a unique complication of the hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is associated with multiple nonrenal manifestations. A unique case is described of a 3-year-old boy who presented with a classic diarrheal prodrome followed by massive necrosis of the biliary tree and common bile duct, pancreas, and the left lobe of his liver. This complication of HUS has not been reported in the English-language literature.

Epigallocatechin gallate and gallocatechin gallate in green tea catechins inhibit extracellular release of Vero toxin from enterohemorrhagic Escherichia coli O157:H7

We studied the effects of six catechin derivatives (catechin, epigallocatechin, epicatechin, epicatechin gallate, epigallocatechin gallate (EGCg) and gallocatechin gallate (GCg)) in green tea on the production and extracellular release of Vero toxins (VTs) from enterohemorrhagic Escherichia coli (EHEC) cultured at 37 degrees C for 24 h. EGCg and GCg in the culture medium markedly inhibited extracellular VTs release from EHEC cells into the culture supernatant fluid at concentrations of 0.05 mg/ml or higher, as estimated by both the reversed passive latex agglutination assay and cytotoxic assay using Vero cells. Production and extracellular release of maltose binding protein, a periplasmic protein, into the culture supernatant were also inhibited by EGCg and GCg, indicating that their inhibitory effect on release from periplasm into the outer milieu is not specific to VTs, but general to the proteins accumulated in EHEC periplasm.

Reactive oxygen species as a risk factor in verotoxin-1-exposed rats

It has been suggested the the interaction of Escherichia coli O157-derived verotoxins (VTs) with the vascular endothelium plays a central role in the pathogenesis of the thrombotic microangiopathy and ischemic lesions characteristic of hemolytic uremic syndrome (HUS) and E. coli O157-associated hemorrhagic colitis. Intravenous administration of both E. coli O157-derived VT1 and lipopolysaccharide (LPS) in the rat induced a synergistic increase in thiobarbituric acid (TBA) values in those animal's plasma, as compared with that injected with VT1 or LPS alone. We then hypothesized that an increase in lipid peroxidation in the rat plasma was due to an enhanced production of endothelial cell-derived reactive oxidant. Based on determination of rat sera and cultured human aortic endothelial cells (HAECs), VT1 had little if any effect on LPS-stimulated increase of nitric oxide and the resultant peroxynitrite generations. Both RT-PCR and Western blot studies of reactive oxygen species-related enzymes showed that VT1 markedly decreased the expression of catalase mRNA and protein in HAECs, but caused less alteration in the levels of Cu, Zn-superoxide dismutase, and NADPH oxidase mRNA. Further studies by spin trapping analysis using 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) revealed a time-dependent increase in hydroxyl radicals by VT1 in HAECs. The accumulated data thus suggest that bacterial VT1 reduces mainly catalase levels in endothelial cells, which is synergistically potentiated by LPS, and that the resulting hydroxyl radical participates in endothelium injury through a marked enhancement of lipid peroxidation, leading to HUS.

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.

Evaluation of enzyme-labeled oligonucleotide probes to identify enterohaemorrhagic Escherichia coli

Alkaline phosphatase-conjugated oligonucleotide probes were developed to detect the gene coding for Vero toxin 1 (VT1) and Vero toxin 2 (VT2). Using these probes, 3 hr was enough to detect VT genes when suspicious colonies of enterohaemorrhagic Escherichia coli (EHEC) were obtained on an agar plate. The results of a hybridization test with 144 isolates of EHEC O157 and one isolate of Shigella dysenteriae Type 1 agreed exactly with the immunological detection, reversed passive latex agglutination (RPLA) test, of VTs in their culture supernatants. The sensitivity levels of these probes for the detection of VT genes were 100%. The specificity of these probes were also tested with a total of 1,002 strains of Escherichia coli other than EHEC and 8 strains of Shigella sp. other than Shigella dysenteriae Type 1; the results showed 100% specificity.

L-arginine as a therapeutic approach for the verotoxigenic Escherichia coli-induced hemolytic uremic syndrome and thrombotic thrombocytopenic purpura

Infection with verotoxigenic Escherichia coli, mainly strain O157:H7, has been incriminated in the cause of the hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Both syndromes, which cause serious problems in children and elderly patients, are not readily treated. Conventional treatment with antibiotics has been reported to not only stimulate bacteria to increase toxin production, but also to enhance its release from the cell. This in turn increases the severity of the disease. An alternative approach to the control of the disease would involve treatment with the amino acid L-arginine, in high amounts through total parenteral nutrition. L-arginine will generate high amounts of nitric oxide which will decrease platelet aggregation and increase vasodilation. Both effects will decrease the development of the tubular occlusion and the accompanied hypertension. In summary, we hypothesize that L-arginine can be used to control two diseases caused by E. coli O157:H7.

Hemolytic disorders associated with cancer

Three principal environmental causes of hemolytic anemia in malignancy have been identified: (1) hemolysis mediated by auto-antibodies to red cells; (2) hemolysis due to microangiopathic disorders; and (3) chemotherapy-induced red cell destruction. These three environmental stressors occur rarely in cancer patients, and they form the subject of this review.

Escherichia coli verotoxin binding to human paediatric glomerular mesangial cells

Haemolytic uraemic syndrome (HUS) remains the leading cause of acute renal failure in children. Although an Escherichia coli-produced verotoxin (VT) has been implicated in the pathogenesis of HUS, the precise mechanisms of disease are not well defined. We hypothesise that the pathogenesis of renal failure in HUS includes the binding of E. coli VT to the glomerular mesangial cell, with consequent effects on renal function. Using human paediatric mesangial cells, we studied the binding and biological effects of the purified verotoxin VT-1. We isolated, purified and characterised paediatric glomerular mesangial cells. The mesangial cells were characterised by their immunoreactivity with both smooth muscle actin and vimentin antibodies, and lack of immunoreactivity with cytokeratin or factor VIII antibodies. Using an fluorescein isothiocyanate-conjugated VT (10(-7)-10(-8) M), we demonstrated specific binding to the mesangial cell membrane by immunofluorescence microscopy. We also demonstrated a dose-dependent inhibition of mesangial cell mitogenesis at concentrations from 10(-9) to 10(-17) M. Our data demonstrate that VT-1 binds to paediatric human glomerular mesangial cells and this binding results in specific biological actions, including an inhibition of cell mitogenesis.

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.

Cisplatin-associated hemolytic uremic syndrome

BACKGROUND

Hemolytic uremic syndrome (HUS) is an acquired disorder largely affecting infants and young children. It is characterized by the triad of microangiopathic hemolytic anemia, acute renal failure, and thrombocytopenia. Although its etiology is unknown, viral and bacterial infections, disseminated malignancies in adults, and a variety of chemotherapeutic agents including cisplatin, have been implicated in its occurrence. The association of HUS with chemotherapeutic agents after its detection in a pediatric patient treated with cisplatin is reviewed.

METHODS

A 16-year-old male with osteosarcoma was treated with cisplatin as part of a chemotherapy protocol. After the fourth course, his renal function deteriorated and necessitated cessation of cisplatin. Nine months after the initiation of cisplatin, HUS developed. There was no evidence of residual tumor or metastatic disease. He received numerous packed erythrocyte and platelet transfusions for persistent hemolysis and underwent several episodes of hemodialysis. Utilizing this patient as an example, the authors reviewed the incidence of HUS developing subsequent to the use of other chemotherapeutic agents.

RESULTS

In the publishing literature, chemotherapy-associated HUS has been described to occur 54 days to 14 months after the initiation of chemotherapeutic regimens. A variety of agents was associated with the phenomenon.

CONCLUSION

Hemolytic uremic syndrome may be a complication of cisplatin, as evidenced by the condition that occurred in a 16-year-old patient with osteosarcoma after cisplatin therapy.

Verotoxin induces hemorrhagic lesions in rat small intestine. Temporal alteration of vasoactive substances

E. coli O157:H7 produces a cytotoxin active against Vero cells that has been termed verotoxin. In this study, we demonstrated that local intraarterial injection of verotoxin induced a decrease in blood flow and an increase in hemorrhagic lesions in rat small intestine. Significant increases in the area of hemorrhagic lesions were observed at 120 min after verotoxin injection. These lesions were produced by either verotoxin 1 or 2, but verotoxin 2 produced more extensive lesions. The temporal alteration of vasoactive substances in microcirculatory beds was determined after the administration of culture filtrate of E. coli O157:H7. Tissue-type plasminogen activator activity in regional plasma was significantly elevated as early as 30 min, suggesting that local fibrinolytic activation mediated by microvascular endothelium occurred. There was also early elevation of platelet-activating factor content in the ileal mucosa and its level remained significantly elevated thereafter. Intestinal blood flow, as determined by a laser Doppler flowmeter, started to decrease at about 45 min. The platelet-activating factor antagonist CV6209 was shown to attenuate the decrease in blood flow as well as the development of hemorrhagic lesions, demonstrating that platelet-activating factor is an important mediator for the microcirculatory damage. Accumulation of neutrophils demonstrated by myeloperoxidase activity in the intestinal mucosa and overproduction of oxygen-radicals from neutrophils of the mesenteric veins determined by the luminol-dependent chemiluminescence assay were observed at 60 min, corresponding with the decreased blood flow. Platelet-activating factor may be closely involved in the process of leukocyte accumulation and increased oxygen radical generation, because CV6209 also significantly attenuated these changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Clostridium septicum sepsis and meningitis as a complication of the hemolytic-uremic syndrome

Hemolytic-uremic syndrome (HUS) is recognized by the triad of acute microangiopathic hemolytic anemia, thrombocytopenia, and oliguric renal failure. The condition is usually preceded by gastroenteritis associated with bloody diarrhea. Escherichia coli 0157:H7, an enterohemorrhagic verotoxin producing E. coli, is now recognized as the most common pathogen associated with hemorrhagic colitis and HUS in North America.1

Since its description, a variety of gastrointestinal and neurologic complications of HUS have been noted. An association between HUS and meningitis due to Hemophilus influenzae 2 and Streptococcus pneumoniae3 has been previously reported. In addition, the first reported case of Clostridium septicum sepsis and cerebritis complicating gastrointestinal involvement in HUS was reported in 1988.4

We report the second confirmed case of fatal C. septicum sepsis and meningitis as a complication of HUS, suggesting that this entity may be more common than previously recognized. We review the epidemiology and clinical manifestations of C. septicum infections and speculate on the pathogenesis of the colitis and invasive C. septicum infection in our patient.

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.

Haemolytic-uraemic syndrome associated with Aeromonas hydrophila enterocolitis

Haemolytic-uraemic syndrome (HUS) associated with Aeromonas hydrophila enterocolitis is reported in a 23-month-old female infant. The A. hydrophila strain isolated from the patient's stool sample produced cytotoxin against verocells; increasing levels of cytotoxin-neutralizing antibody in the patient's sera were demonstrated, suggesting a recent infection. This report indicates that A. hydrophila should be suspected as a possible cause of HUS, and that this pathogen should be looked for in cases of post-diarrhoeal HUS.

The use of intravenous gammaglobulin in the treatment of typical hemolytic uremic syndrome

Nine children with acute typical post-diarrhea hemolytic uremic syndrome (HUS) were treated with intravenous gammaglobulin (IVIG). These children were compared to nine children with HUS who did not receive IVIG. The use of IVIG did not appear to have a beneficial effect on eight of the nine treated children. There were no significant differences found in the duration of hemorrhagic colitis, thrombocytopenia, elevation of the white blood count (WBC), anuria, dialysis, or hospitalization, or the presence of a central nervous system complication or pancreatitis. Although no significant difference was found in the duration of thrombocytopenia, there was a trend towards a longer duration of thrombocytopenia in children treated with IVIG (P = 0.13). One child demonstrated both an increase in her platelet count and a decrease in her WBC count within 24 h of receiving her first dose of IVIG.

Haemolytic uraemic syndrome: 17 years' experience in a Scottish paediatric renal unit

Seventy-nine children with the Haemolytic Uraemic Syndrome were referred to our unit between 1972 and 1988. The typical summer peak incidence was seen. A diarrhoeal prodrome occurred in 71 (90%). Fifty-nine (75%) required dialysis and 74 (94%) blood transfusion. Extra-renal disease was documented: neurological 32 (40%); abdominal 11 (14%); diabetes mellitus one case. Fifty-one (61%) had acute hypertension. The acute mortality rate was 9%. Children with neurological features had greater biochemical disturbances and longer duration of dialysis. Fifty-nine children were followed for a mean 47.4 months. Forty-four (75%) are healthy. Nine (15%) have renal impairment, two have proteinuria, one hypertension and one has a residual hemiparesis. There were two late deaths. Presence of acute neurological features increased risk of early death or survival with sequelae. Prolonged dialysis was significantly associated with poorer outcome. However, there were no reliable early indicators of poor prognosis.

Surgical complications of the hemolytic-uremic syndrome

Hemolytic-uremic syndrome (HUS) of childhood is a triad of acute hemolytic anemia, thrombocytopenia, and acute renal failure associated with a gastrointestinal prodrome. From 1977 to 1988, 134 patients with HUS were admitted to this institution. All patients presented with abdominal pain and diarrhea, which was virtually always bloody. Seventy-eight patients (60%) required dialysis. Five patients died (4%). One patient died as a result of colon perforation, the other four patients died of other nonsurgical complications of HUS. Three patients underwent exploratory laparotomy. One patient had a hemoperitoneum from mesenteric and transmural bleeding of the entire intraabdominal colon. Another patient had undergone surgery elsewhere for presumed intussusception with pancolitis found at exploration. Fourteen days postoperatively, he had a spontaneous perforation of the transverse colon. The third patient presented with pancolitis and perforation of the transverse colon. Despite surgical intervention he died on the sixth postoperative day. One other patient was treated conservatively for pancreatitis, which developed 3 weeks after her presentation with HUS. Complications requiring surgical intervention in HUS are rare, potentially lethal, and usually involve the colon.

Hemolytic-uremic syndrome in children. A serious hazard of undercooked beef

Hemolytic-uremic syndrome is the leading cause of acute renal failure in childhood. Its incidence in North America is increasing. Escherichia coli O157:H7 is the most common infectious trigger and is spread by contaminated beef products as well as from person to person. Antibiotics or antidiarrheal medications should not be used in the treatment of E coli hemorrhagic colitis or hemolytic-uremic syndrome. Mortality in children with the syndrome has fallen to less than 10% in North America, largely because of careful attention to nutrition, maintenance of a normal fluid and electrolyte balance, and careful monitoring. Education and emotional support of the family are important aspects of the treatment program.

Evaluation of DNA probes for detection of Shiga-like-toxin-producing Escherichia coli in food and calf fecal samples

The use of DNA probes for Shiga-like toxin I (SLT-I) and SLT-II for detection of SLT-producing Escherichia coli (SLTEC) in foods and calf fecal samples was evaluated. Enrichment cultures were prepared from food or fecal samples. Colonies formed by plating of enrichment cultures were probed for SLTEC by colony hybridization. Alternatively, enrichment cultures were analyzed for SLTEC presence by dot blot. The lowest detected concentration of SLTEC in sample homogenates inoculated with E. coli O157:H7 corresponded to 1.3 CFU/g of sample. Of the 44 food samples and 28 fecal samples from dairy calves tested by the colony hybridization method, 4 food samples, including ground beef, raw goat milk, blueberries, and surimi-based delicatessen salad, and 9 calf fecal samples were positive with the SLT probes. The dot blot technique yielded results within 48 h and can be used as a fast and sensitive method of detection for SLTEC in foods and calf fecal samples. The colony hybridization technique took 3 to 4 days but permits recovery of the positive colonies when desired.

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.

Cloning and nucleotide sequencing of Vero toxin 2 variant genes from Escherichia coli O91:H21 isolated from a patient with the hemolytic uremic syndrome

Cellular DNA extracted from Escherichia coli strain B2F1 (O91:H21) was found to contain two separate DNA sequences that hybridized with a Vero toxin 2 (VT2)-specific gene probe under stringent conditions. These two sequences were cloned and both were shown to encode a variant of Vero toxin 2 (VT2vh). The nucleotide sequences of the operons encoding VT2vh, designated as vtx2ha and vtx2hb, were determined. The two operons were nearly identical (99% overall DNA homology) and both encoded A subunits of 319 amino acid residues and B subunits of 89 amino acid residues, the A and B subunit genes being separated by a stretch of 14 bp. The A and B subunit genes of the vtx2ha operon exhibited 98.6% and 95.5% DNA homology, respectively, with those of the slt-II operon encoding Shiga-like toxin II (or VT2) cloned from a strain from a patient with hemorrhagic colitis, while the A and B subunit genes of the vtx2ha operon showed 94.5% and 82.8% DNA homology, respectively, with those of the slt-IIv operon encoding a SLT-II variant cloned from a strain isolated from a pig with edema disease. The nucleotide sequences of the presumed promoters and presumptive ribosome binding sites in the vtx2ha, vtx2hb, and slt-II, and slt-IIv operons were identical. These results indicate that nucleotide sequences encoding a family of VT2-related toxins are present in various strains of E. coli and that the sequences of the genes for A subunits are better conserved than those of the B subunit genes.

Bacterial endotoxin both enhances and inhibits the toxicity of Shiga-like toxin II in rabbits and mice

The ability of bacterial lipopolysaccharide (LPS) to enhance the toxicity of Shiga-like toxin II (SLT-II) was investigated in rabbits and mice. Rabbits were continuously infused with 0.5 50% lethal dose (LD50) of SLT-II per day. Rabbits that received a 30-micrograms/kg dose of LPS (0.02 LD50) on day 3 of infusion were significantly more likely to die than were rabbits receiving SLT-II only. Rabbits receiving SLT-II and a lower dose of LPS (3 micrograms/kg) did not die but lost an average 3.3% +/- 1.0% of initial body weight during the first 5 days of infusion, compared with weight gains of 4.2% +/- 0.6% and 17.1% +/- 0.9% for rabbits receiving only SLT-II or LPS, respectively. Rabbits that were pretreated with LPS 20 h before challenge with a single dose of SLT-II showed highly significant protection from both the diarrheagenic and lethal effects of SLT-II. Pretreatment of endotoxin-responsive C3H/HeN mice protected the animals from challenge with an LD50 but not an LD100 of SLT-II. LPS enhanced the lethal toxicity of SLT-II for C3H/HeN mice when it was given at 8 or 24 h but not 0 or 72 h after SLT-II challenge. LPS did not affect the lethal toxicity of SLT-II for endotoxin-resistant C3H/HeJ mice. These results suggest that LPS enhances the effects of SLT-II in vivo. Since cecal changes that increase mucosal permeability occur in response to SLT in rabbits, this synergy may be directly relevant to disease processes.