THE HEMOLYTIC-UREMIC SYNDROME

Progression of renal damage and tubular regeneration in pregnant and non-pregnant adult female rats inoculated with a sublethal dose of Shiga toxin 2

BACKGROUND

Shiga toxin-producing Escherichia coli is the main cause of post-diarrheal hemolytic uremic syndrome (HUS) which produces acute kidney injury mainly in children, although it can also affect adults. The kidneys are the organs most affected by Shiga toxin type 2 (Stx2) in patients with HUS. However, previous studies in pregnant rats showed that a sublethal dose of Stx2 causes severe damage in the uteroplacental unit and induces abortion, whereas produces mild to moderate renal damage. The aim of the present work was to study the progression of renal injury caused by a sublethal dose of Stx2, as well as renal recovery, in pregnant and non-pregnant rats, and to investigate whether pregnancy physiology may affect renal damage progression mediated by Stx2.

METHODS

Renal function and histopathology was evaluated in pregnant rats intraperitoneally injected with a sublethal dose of Stx2 (0.5 ng/g bwt) at the early stage of gestation (day 8 of gestation), and results in these rats were compared over time with those observed in non-pregnant female rats injected with the same Stx2 dose. Hence, progression of cell proliferation and dedifferentiation in renal tubular epithelia was also investigated.

RESULTS

The sublethal dose of Stx2 induced abortion in pregnant rats as well as a significant more extended functional and histological renal injury in non-pregnant rats than in pregnant rats. Stx2 also caused decreased ability to concentrate urine in non-pregnant rats compared to their controls. However, renal water handling in pregnant rats was not altered by Stx2, and was significantly different than in non-pregnant rats. The greatest renal injury in both pregnant and non-pregnant rats was observed at 4 days post-Stx2 injection, and coincided with a significant increase in tubular epithelial proliferation. Expression of mesenchymal marker vimentin in tubular epithelia was consistent with the level of tubular damage, being higher in non-pregnant rats than in pregnant rats. Recovery from Stx2-induced kidney injury was faster in pregnant rats than in non-pregnant rats.

CONCLUSIONS

Adaptive mechanisms developed during pregnancy such as changes in water handle and renal hemodynamic may contribute to lessen the Stx2-induced renal injury, perhaps at the expense of fetal loss.

A decrease in the incidence of Shiga toxin-related hemolytic uremic syndrome as a cause of kidney transplantation at an argentine referral center

BACKGROUND

In Argentina, Hemolytic uremic syndrome caused by Shiga toxin-producing Escherichia coli (STEC HUS), is the main cause of acute kidney injury and the second cause of end-stage renal disease (ESRD) in children. In recent decades, strategies have been implemented to reduce progression to ESRD, but it is not known whether the cumulative incidence of HUS requiring kidney transplantation (KTx) has decreased. We aimed to determine whether the cumulative incidence of STEC HUS in children undergoing KTx decreased and compared outcomes of HUS-related KTx vs. those related to other etiologies.

METHODS

All patients who underwent KTx at our institution were evaluated. The cohort was divided into quintiles (Q), and we compared the cumulative incidence of HUS-related KTx vs KTx due to other etiologies.

RESULTS

A total of 1000 consecutive KTx were included. The cumulative incidence of HUS-related KTx was 11%. HUS was the second cause of KTx in Q1: 17% (1988-1995); Q2: 13.5% (1996-2003); Q3: 11.5% (2004-2009) and third cause in Q4: 10% (2010-2015) and Q5: 3% (2016-2021). The cumulative incidence of HUS-related KTx decreased in Q4 and Q5 compared to Q1, Q2, and Q3 and the decline was even steeper when comparing Q4 to Q5 (p:0.019). There was no difference in graft survival in patients with HUS vs. congenital anomalies of kidney and urinary tract (CAKUT) but better than in those with focal segmental glomerulosclerosis (FSGS).

CONCLUSIONS

In this cohort, the cumulative incidence of HUS-related KTx decreased, which may have been due to the implementation of nephroprotective strategies.

Ocular involvement in STEC-associated hemolytic uremic syndrome

BACKGROUND

Hemolytic uremic syndrome (HUS) is a systemic thrombotic microangiopathy characterized by hemolytic anemia, thrombocytopenia, and variable kidney involvement. Extrarenal thrombotic microangiopathy occurs in central nervous system (CNS), colon, and other organ systems, but ocular involvement is rarely recognized. This study aimed to analyze frequency and severity of ocular involvement in STEC-HUS, and the relationship between ocular involvement and disease severity, with emphasis on CNS, kidney, and colonic disease.

METHODS

Prospective, longitudinal, observational study.

INCLUSION CRITERIA

STEC-HUS patients September 2014-January 2019. Funduscopic examination (FE) was performed within 48 h of admission. We evaluated severity of CNS disease, kidney involvement, and presence of hemorrhagic colitis (HC).

RESULTS

Ninety-nine patients were included (female 52), mean age 39.4 months (DE: 29.8; range 9-132). Thirteen patients (13.1%) had abnormal FE, 10 showing variable degrees of hemorrhagic exudates and 2 with typical Purtscher-like retinopathy. Other findings included tortuous vascularity, cotton wool spots, and transient retinal edema. CNS involvement was present in 16/99 patients, severe in 12 (75%). Abnormal FE occurred in 5/12 (31%) patients with severe CNS involvement vs. 8/87 (9.2%) with mild, moderate, or no CNS disease (p = 0.0191). Abnormal FE was present in 2/33 (6%) patients without dialysis vs. 11/66 (16.6%) requiring dialysis (p = 0.20). Finally, there were FE abnormalities in 6/20 patients with HC vs. 7/79 without HC (p = 0.012).

CONCLUSIONS

FE abnormalities were present in 13% of HUS patients. Abnormal FE significantly associated with more severe disease, including severe CNS involvement and HC. We suggest FE should be performed in severe HUS, especially in cases with severe CNS disease. A higher resolution version of the Graphical abstract is available as Supplementary information.

Hyperuricemia: an unrecognized risk factor for kidney-related sequelae in children with hemolytic uremic syndrome

BACKGROUND

Chronic kidney-related sequelae after STEC-HUS occur in 20-40% of patients. Hyperuricemia (HU) may cause acute and chronic toxicity involving the kidneys. We retrospectively assessed if there was an association between the presence of HU during the acute illness and that of kidney-related sequelae in children with STEC-HUS.

METHODS

Children with STEC-HUS who had clinical and laboratory data at 2 years of follow-up were included in this case-control study. Univariate and multivariate analyses were performed between patients with (cases) or without (controls) kidney-related sequelae to identify factors associated with outcomes, including different measures of serum uric acid (sUA) (baseline level, peak, and duration of HU). HU was defined as sUA > 8 mg/dL.

RESULTS

Of 86 patients included, 77.9% had HU. Patients with sequelae (n = 41) had a higher prevalence of HU (41/41 vs. 26/45, p < 0.01), higher baseline leukocyte count, serum creatinine (sCr), and sUA levels as well as lower sodium than controls. During hospitalization, cases also had higher sCr peak, sUA peak and duration of HU, requirement and duration of dialysis, extrarenal complications, and hypertension. By multivariate analysis, after adjusting for length of dialysis, only duration of HU (p = 0.0005; OR 1.7, 95% CI 1.27-2.36) remained as an independent predictor of sequelae, with a best cutoff of 5.5 days (AUC 0.95, specificity 80%, sensitivity 100%).

CONCLUSIONS

The presence of HU is a common finding in children with STEC-HUS and its duration during the acute stage was associated with kidney-related sequelae, regardless of the duration of dialysis. A higher resolution version of the Graphical abstract is available as Supplementary Information.

Eliglustat prevents Shiga toxin 2 cytotoxic effects in human renal tubular epithelial cells

BACKGROUND

Shiga toxin-producing Escherichia coli is responsible for post-diarrheal (D+) hemolytic uremic syndrome (HUS), which is a cause of acute renal failure in children. The glycolipid globotriaosylceramide (Gb3) is the main receptor for Shiga toxin (Stx) in kidney target cells. Eliglustat (EG) is a specific and potent inhibitor of glucosylceramide synthase, first step of glycosphingolipid biosynthesis, actually used for the treatment of Gaucher's disease. The aim of the present work was to evaluate the efficiency of EG in preventing the damage caused by Stx2 in human renal epithelial cells.

METHODS

Human renal tubular epithelial cell (HRTEC) primary cultures were pre-treated with different dilutions of EG followed by co-incubation with EG and Stx2 at different times, and cell viability, proliferation, apoptosis, tubulogenesis, and Gb3 expression were assessed.

RESULTS

In HRTEC, pre-treatments with 50 nmol/L EG for 24 h, or 500 nmol/L EG for 6 h, reduced Gb3 expression and totally prevented the effects of Stx2 on cell viability, proliferation, and apoptosis. EG treatment also allowed the development of tubulogenesis in 3D-HRTEC exposed to Stx2.

CONCLUSIONS

EG could be a potential therapeutic drug for the prevention of acute kidney injury caused by Stx2.

IMPACT

For the first time, we have demonstrated that Eliglustat prevents Shiga toxin 2 cytotoxic effects on human renal epithelia, by reducing the expression of the toxin receptor globotriaosylceramide. The present work also shows that Eliglustat prevents Shiga toxin 2 effects on tubulogenesis of renal epithelial cells. Eliglustat, actually used for the treatment of patients with Gaucher's disease, could be a therapeutic strategy to prevent the renal damage caused by Shiga toxin.

Stx2 Induces Differential Gene Expression and Disturbs Circadian Rhythm Genes in the Proximal Tubule

Shiga toxin-producing Escherichia coli (STEC) causes proximal tubular defects in the kidney. However, factors altered by Shiga toxin (Stx) within the proximal tubules are yet to be shown. We determined Stx receptor Gb3 in murine and human kidneys and confirmed the receptor expression in the proximal tubules. Stx2-injected mouse kidney tissues and Stx2-treated human primary renal proximal tubular epithelial cell (RPTEC) were collected and microarray analysis was performed. We compared murine kidney and RPTEC arrays and selected common 58 genes that are differentially expressed vs. control (0 h, no toxin-treated). We found that the most highly expressed gene was GDF15, which may be involved in Stx2-induced weight loss. Genes associated with previously reported Stx2 activities such as src kinase Yes phosphorylation pathway activation, unfolded protein response (UPR) and ribotoxic stress response (RSR) showed differential expressions. Moreover, circadian clock genes were differentially expressed, suggesting Stx2-induced renal circadian rhythm disturbance. Circadian rhythm-regulated proximal tubular Na⁺-glucose transporter SGLT1 (SLC5A1) was down-regulated, indicating proximal tubular functional deterioration, and mice developed glucosuria confirming proximal tubular dysfunction. Stx2 alters gene expression in murine and human proximal tubules through known activities and newly investigated circadian rhythm disturbance, which may result in proximal tubular dysfunctions.

Hypoalbuminemia: a risk factor in patients with STEC-associated hemolytic uremic syndrome

BACKGROUND

We aimed to determine the prevalence of hypoalbuminemia in STEC-HUS patients with hemorrhagic colitis (HC) and whether serum albumin level (SAL), leukocyte count, hematocrit and serum sodium level (SSL) are prognostic markers of HC, central nervous system disease (CNSd) and/or dialysis requirement and evaluate if hypoalbuminemia is associated with fecal protein losses.

METHODS

We prospectively evaluated STEC-HUS patients treated at our institution from 9/2011 to 2/2019, analyzing the presence of HC, CNSd and dialysis requirement and SAL, SSL, leukocytes, hematocrit and α1-antitrypsin clearance.

RESULTS

We evaluated 98 patients, with mean age of 33.3 months. SAL ≤ 29.5 g/l, > 24,600 leukocytes/mm³ and hematocrit > 30% behave as independent prognostic markers for HC. SAL ≤ 28 g/l, > 25,200 leukocytes/mm³ and hematocrit > 30% behave as prognostic markers for CNSd. SAL ≤ 31.6 g/l, > 13,800 leukocytes/mm³, hematocrit > 18.9% and hyponatremia (≤ 132 mEq/l) behave as prognostic markers for dialysis requirement. However, in multivariate logistic regression models, only hypoalbuminemia behaved as a risk factor for HC, CNSd and dialysis. α1-antitrypsin clearance was performed in 69 patients and was high in 9/69 (13%), only 4 with HC. No significant association was observed between α1-antitrypsin clearance and albuminemia (χ² = 0.1076, p = 0.7429) as well as α1-antitrypsin clearance and HC (χ² = 1.7892, p = 0.1810).

CONCLUSIONS

Almost all patients with HC had hypoalbuminemia, which behaves as a risk factor for HC, CNSd and dialysis requirement. No significant association was observed between elevated α1-antitrypsin clearance and hypoalbuminemia nor between elevated α1-antitrypsin clearance and HC. These findings could be related to the small number of evaluated patients.

Cardiac Manifestation among Children with Hemolytic Uremic Syndrome

OBJECTIVE

The primary objectives of the study were to describe the association between cardiac manifestations and in-hospital mortality among children with hemolytic uremic syndrome.

STUDY DESIGN

Using the Pediatric Health Information System database, this retrospective, multicenter, cohort study identified the first hemolytic uremic syndrome-related inpatient visit among children ≤18 years (years 2004-2018). The frequency of selected cardiac manifestations and mortality rates were calculated. Multivariate analysis identified the association of specific cardiac manifestations and the risk of in-hospital mortality.

RESULTS

Among 3915 patients in the analysis, 238 (6.1%) had cardiac manifestations. A majority of patients (82.8%; n = 197) had 1 cardiac condition and 17.2% (n = 41) had ≥2 cardiac conditions. The most common cardiac conditions was pericardial disease (n = 102), followed by congestive heart failure (n = 46) and cardiomyopathy/myocarditis (n = 34). The percent mortality for patients with 0, 1, or ≥2 cardiac conditions was 2.1%, 17.3%, and 19.5%, respectively. Patients with any cardiac condition had an increased odds of mortality (OR, 9.74; P = .0001). In additional models, the presence of ≥2 cardiac conditions (OR, 9.90; P < .001), cardiac arrest (OR, 38.25; P < .001), or extracorporeal membrane oxygenation deployment (OR, 11.61; P < .001) were associated with increased risk of in-hospital mortality.

CONCLUSIONS

This study identified differences in in-hospital mortality based on the type of cardiac manifestations, with increased risk observed for patients with multiple cardiac involvement, cardiac arrest, and extracorporeal membrane oxygenation deployments.

Acute peritoneal dialysis, complications and outcomes in 389 children with STEC-HUS: a multicenter experience

BACKGROUND

Management of acute kidney injury (AKI) in children with hemolytic uremic syndrome induced by a Shiga toxin-producing Escherichia coli infection (STEC-HUS) is supportive; however, 40 to 60% of cases need kidney replacement therapy (KRT). The aim of this study was to analyze procedure complications, especially peritonitis, and clinical outcomes in children with AKI secondary to STEC-HUS treated with acute PD.

METHODS

This is a multicenter retrospective study conducted among thirty-seven Argentinian centers. We reviewed medical records of 389 children with STEC-HUS hospitalized between January 2015 and February 2019 that required PD.

RESULTS

Complications associated with PD were catheter malfunction (n = 93, 24%), peritonitis (n = 75, 19%), fluid leaks (n = 45, 11.5%), bleeding events (n = 23, 6%), and hyperglycemia (n = 8, 2%). In the multivariate analysis, the use of antibiotic prophylaxis was independently associated with a decreased risk of peritonitis (hazard ratio 0.49, IC 95% 0.29-0.81; p = 0.001), and open-surgery catheter insertion was independently associated with a higher risk (hazard ratio 2.8, IC 95% 1.21-6.82; p = 0.001). Discontinuation of PD due to peritonitis, severe leak, or mechanical complications occurred in 3.8% of patients. No patient needed to be transitioned to other modality of KRT due to inefficacy of the technique. Mortality during the acute phase occurred in 2.8% patients due to extrarenal complications (neurological and cardiac involvement), not related to PD.

CONCLUSIONS

Acute PD was a safe and effective method to manage AKI in children with STEC-HUS. Prophylactic antibiotics prior to insertion of the PD catheter should be considered to decrease the incidence of peritonitis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Fluid restriction versus volume expansion in children with diarrhea-associated HUS: a retrospective observational study

BACKGROUND

Fifty percent of patients with typical diarrhea-associated hemolytic uremic syndrome (D+HUS) require kidney replacement therapy (KRT). In these patients, dehydration worsens disease prognosis. We evaluated dialysis requirement, presence of seizures, and mortality rate among patients diagnosed with D+HUS treated with volume expansion (VE) versus fluid restriction (FR).

METHODS

Thirty-five patients with D+HUS were enrolled; 16 received VE and 19 were historical patients who received conventional FR.

RESULTS

Upon admission or during treatment, neither group presented evidence of fluid overload. The VE group received higher volumes of saline (VE 27 ml/kg [10-30] over a 3-h period vs. FR 0 ml), had higher urine output after 12 h (VE vs. FR: OR 6.2 [1.2-41.6], P = 0.03), and required less dialysis (VE 2 [12.5%, CI 95% 0-29] vs. FR 9 [47.4%, CI 95% 24-70], P = 0.035). The VE group had an absolute risk reduction of 0.34 (CI 95% 0.07-0.63); hence, three patients treated with VE were required to avoid one KRT. VE also corrected initial hyponatremia and maintained serum sodium within normal ranges. No statistical differences were observed regarding number of patients with seizures (P = 0.08) or mortality (P = 1.0).

CONCLUSIONS

VE markedly reduces the number of patients requiring KRT and keeps serum sodium within a normal range. We propose to initially hydrate every patient with D+HUS and without signs of fluid overload, with 10 ml/kg/h 0.9% saline solution IV, over a 3-h period. Afterwards, if urine output is ≥ 0.5 ml/kg/h, it is recommended to not dialyze and continue IV hydration schedule with isotonic (D5) saline solution, according to their needs.

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

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

History of Peritoneal Dialysis in Latin America

Latin America is a region formed by a number of countries of Latin heritage in which the common languages spoken are Spanish and Portuguese. Latin America was not isolated from the evolution of peritoneal dialysis (PD) throughout the rest of the world, as evidenced by the fact that, between the 1940s and the 1960s, PD was used to treat acute renal failure patients and later for the intermittent treatment of end-stage renal failure patients. The true development of PD took place toward the end of the 1970s and beginning of the 1980s with the introduction of continuous ambulatory peritoneal dialysis (CAPD).

It is evident that the introduction of CAPD in most countries was a result of the personal effort and interest of individuals or groups of nephrologists. Initially, PD was not always implemented under ideal circumstances; locally manufactured, improvised supplies were associated with poor results. The arrival of companies with appropriate equipment and supplies led to widespread dissemination of this new modality. Furthermore, regulations and reimbursement by health authorities were additional obstacles.

It is clear that PD in Latin America is still largely utilized to treat acute renal failure patients, particularly in countries where hemodialysis is not readily available. It is still employed intermittently to manage end-stage renal failure patients when hemodialysis is not available. With the exception of Colombia and Mexico, CAPD penetration is below 10%.

While CAPD is nonexistent in certain countries, such as Cuba, due to lack of supplies, in other countries, such as Chile, it is restricted to patients that cannot be placed or continued on hemodialysis, those for example who lack vascular access, or those from remote rural areas. In addition, automated PD is relatively more costly and is therefore restricted in some countries.

[Biomedical knowledge and health policies: Hemolytic Uremic Syndrome and Fibromyalgia]

The article deals with the construction of knowledge about diseases. The general objective is to analyze the process of constructing scientific knowledge of two diseases in comparative perspective: Hemolytic Uremic Syndrome and Fibromyalgia. The work reflects on the construction of biomedical knowledge and health policies, specifically how scientific knowledge impacts on the design of policies. Our research strategy was based on the analysis of scientific literature, health programs and bills of Argentina. The analysis was based on the axial model of diagnostic categories (semiological, morphological, explanatory and epidemiological) developed by Camargo Jr in order to detect how the distinctive features of biomedical sphere is translated into the political sphere. The investigation showed that the hierarchy given to each axis when a disease is defined at the moment of designing health policies is curcial. It also revealed that when biomedicine can not define the disease, based on their clinical and epidemiological reasoning, the roles are reversed. Then it is politics that recognizes the disease and gives the legitimacy that patients need.

Hyponatremia: a new predictor of mortality in patients with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome

OBJECTIVES

(1) Evaluate mortality rate in patients with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome, (2) determine the leading causes of death, and (3) identify predictors of mortality at hospital admission.

METHODS

We conducted a multicentric, observational, retrospective, cross-sectional study. It included patients under 18 years old with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome hospitalized between January 2005 and June 2016. Clinical and laboratory data were obtained from the Argentine National Epidemiological Surveillance System of Hemolytic Uremic Syndrome. Clinical and laboratory variables were compared between deceased and non-deceased patients. Univariate and multivariate analyses were performed. ROC curves and area under the curve were obtained.

RESULTS

Seventeen (3.65%) out of the 466 patients died, being central nervous system involvement the main cause of death. Predictors of death were central nervous system involvement, the number of days since the beginning of diarrhea to hospitalization, hyponatremia, high hemoglobin, high leukocyte counts, and low bicarbonate concentration on admission. In the multivariate analysis, central nervous system involvement, sodium concentration, and hemoglobin were independent predictors. The best cut off for sodium was ≤ 128 meq/l and for hemoglobin ≥ 10.8 g/dl.

CONCLUSIONS

Mortality was low in children with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome, being central nervous system involvement the main cause of death. The best mortality predictors found were central nervous system involvement, hemoglobin, and sodium concentration. Hyponatremia may be a new Shiga toxin-producing Escherichia coli hemolytic uremic syndrome mortality predictor.

Genotypic Features of Clinical and Bovine Escherichia coli O157 Strains Isolated in Countries with Different Associated-Disease Incidences

There is great geographical variation in the frequency of Escherichia coli O157 infections that correlates with important differences in the bovine reservoir of each country. Our group carried out a broad molecular characterization of human and bovine E. coli O157 strains circulating in Argentina using different methodologies. Our data allows us to conclude that in Argentina, a high homogeneity is observed in both cattle and human strains, with almost exclusive circulation of strains belonging to the hypervirulent clade 8 described by Manning. The aim of this review was to compare the genetic background of E. coli O157 strains isolated in countries that have conducted similar studies, to try to correlate specific O157 genotypes with the incidence and severity of E. coli O157 associated diseases. The characteristics of the strains that cause disease in humans reflect the predominant genotypes in cattle in each of the countries analyzed. The main features clearly linked to high incidence or severity of E. coli O157 infections are lineage-specific polymorphism assay-6 lineage I/II, clade 8 strains and probably, clade 6 strains, the stx_2a/stx_2c genotype, the presence of q933 and q21 simultaneously, and putative virulence factor EC_3286. In countries with an absence of these features in O157 strains, the overall incidence of O157 disease is low. Argentina, where these characteristics are detected in most strains, shows the highest incidence of hemolytic uremic syndrome (HUS) worldwide.

A recombinant O-polysaccharide-protein conjugate approach to develop highly specific monoclonal antibodies to Shiga toxin-producing Escherichia coli O157 and O145 serogroups

Shiga toxin-producing Escherichia coli (STEC) is the major etiologic agent of hemolytic-uremic syndrome (HUS). The high rate of HUS emphasizes the urgency for the implementation of primary prevention strategies to reduce its public health impact. Argentina shows the highest rate of HUS worldwide, being E. coli O157 the predominant STEC-associated HUS serogroup (>70%), followed by E. coli O145 (>9%). To specifically detect these serogroups we aimed at developing highly specific monoclonal antibodies (mAbs) against the O-polysaccharide (O-PS) section of the lipopolysaccharide (LPS) of the dominant STEC-associated HUS serogroups in Argentina. The development of hybridomas secreting mAbs against O157 or O145 was carried out through a combined immunization strategy, involving adjuvated-bacterial immunizations followed by immunizations with recombinant O-PS-protein conjugates. We selected hybridoma clones that specifically recognized the engineered O-PS-protein conjugates of O157 or O145 serogroups. Indirect ELISA of heat-killed bacteria showed specific binding to O157 or O145 serogroups, respectively, while no cross-reactivity with other epidemiological important STEC strains, Brucella abortus, Salmonella group N or Yersinia enterocolitica O9 was observed. Western blot analysis showed specific recognition of the sought O-PS section of the LPS by all mAbs. Finally, the ability of the developed mAbs to bind the surface of whole bacteria cells was confirmed by flow cytometry, confocal microscopy and agglutination assays, indicating that these mAbs present an exceptional degree of specificity and relative affinity in the detection and identification of E. coli O157 and O145 serogroups. These mAbs may be of significant value for clinical diagnosis and food quality control applications. Thus, engineered O-PS specific moieties contained in the recombinant glycoconjugates used for combined immunization and hybridoma selection are an invaluable resource for the development of highly specific mAbs.

Effects of shiga toxin 2 on cellular regeneration mechanisms in primary and three-dimensional cultures of human renal tubular epithelial cells

Shiga toxin (Stx)-producing Escherichia coli (STEC) causes post-diarrheal Hemolytic Uremic Syndrome (HUS), which is one of the most common causes of acute renal failure in children in Argentine. The aim of the present work was to study the effects of Shiga toxin type 2 (Stx2) on regenerative mechanisms of primary cultures of human cortical renal tubular epithelial cells (HRTEC) and three-dimensional (3D) cultures of HRTEC. Primary cultures of HRTEC were able to develop tubular structures when grown in matrigel, which showed epithelial cells surrounding a central lumen resembling the original renal tubules. Exposure to Stx2 inhibited tubulogenesis in 3D-HRTEC cultures. Moreover, a significant increase in apoptosis, and decrease in cell proliferation was observed in tubular structures of 3D-HRTEC exposed to Stx2. A significant reduction in cell migration and vimentin expression levels was observed in HRTEC primary cultures exposed to Stx2, demonstrating that the holotoxin affected HRTEC dedifferentiation. Furthermore, a decreased number of cells expressing CD133 progenitor marker was found in HRTEC cultures treated with Stx2. The CD133 positive cells also expressed the Stx receptor globotriaosylceramide, which may explain their sensitivity to Stx2. In conclusion, Stx2 affects the regenerative processes of human renal tubular epithelial cells in vitro, by inhibiting cell dedifferentiation mechanisms, as well as tubules restoration. The development of 3D-HRTEC cultures that resemble original human renal proximal tubules is a novel in vitro model to study renal epithelial repair mechanisms after injury.

Genetic features of human and bovine Escherichia coli O157:H7 strains isolated in Argentina

Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens associated with human diseases. In Argentina, O157:H7 is the dominant serotype in hemolytic uremic syndrome (HUS) cases. Previously, we have described the almost exclusive circulation of human E. coli O157 strains belonging to the hypervirulent clade 8 in Neuquén Province. The aim of the present study was to investigate, by a broad molecular characterization, if this particular distribution of E. coli O157 clades in Neuquén is similar to the situation in other regions of the country and if it may be originated in a similar profile in cattle, its main reservoir. Two-hundred and eighty O157 strains (54 bovine and 226 human) isolated between 2006 and 2008 in different regions of Argentina were studied. All strains harbored rfbO157, fliCH7, eae, and ehxA genes. The predominant genotype was stx2a/stx2c in human (76.1%) and bovine (55.5%) strains. All human isolates tested by Lineage-Specific Polymorphism Assay (LSPA-6), were lineage I/II; among bovine strains, 94.1% belonged to lineage I/II and 5.9% to lineage I. No LSPA-6 lineage II isolates were detected. Single nucleotide polymorphism (SNP) analysis has revealed the existence of nine clade phylogenetic groups. In our clinical strains collection, 87.6% belonged to the hypervirulent clade 8, and 12.4% were classified as clade 4/5. In bovine isolates, 59.3% strains were clade 8, 33.3% clade 4/5 and 7.4% clade 3. More than 80% of human strains showed the presence of 6 of the 7 virulence determinants described in the TW14359 O157 strain associated with the raw spinach outbreak in the U.S. in 2006. More than 80% of bovine strains showed the presence of 3 of these factors. The q933 allele, which has been related to high toxin production, was present in 98.2% of clinical strains and 75.9% of the bovine isolates. The molecular characterization of human STEC O157 strains allows us to conclude that the particular situation previously described for Neuquén Province, may actually be a characteristic of the whole country. These genetic features are quite similar to those observed in the bovine reservoir and may be derived from it. This data confirms that, unlike the rest of the world, in Argentina most of the STEC O157 strains present in cattle may cause human infections of varying severity and the marked virulence described for these strains may be related to the high incidence of HUS in our country.

Relationship between red blood cell transfusion requirements and severity of renal disease during the acute stage of hemolytic uremic syndrome

BACKGROUND

We performed a retrospective evaluation of patients with diarrhea-associated hemolytic uremic syndrome (D + HUS) with the aims of: (1) determining the rate of red blood cell (RBC) transfusions; (2) establishing the relationship between need for RBC transfusion and severity of renal involvement; (3) determining whether precise measurements of lactic dehydrogenase (LDH) levels can predict the rate of hemolysis and severity of renal disease.

METHODS

A total of 288 patients with D + HUS were retrospectively divided into three groups based on dialysis treatment: group 1, no dialysis treatment (144 patients); group 2, dialysis for 1-10 days (67 patients); group 3, dialysis for ≥11 days (77 patients).

RESULTS

Of the patients in groups 1, 2 and 3, 73.6, 86.5 and 83.1%, respectively, required at least one RBC transfusion. The number of RBC transfusions in groups 1, 2 and 3 was 163, 107 and 162, respectively. Comparison of the groups revealed that the number of RBC transfusions was significantly higher in patients in groups 2 and 3 than in those in group 1 (p = 0.0001). Most RBC transfusions (94.2%) occurred during the first 2 weeks of the disease. The median peak LDH level was 2091 U/l in 32 patients with no RBC transfusion (group A), 3900 U/l in 73 patients with one transfusion (group B) and 6378 U/l in 62 patients with two or more transfusions (group C). Patients who received two or more RBC transfusions had a significantly higher median peak LDH level than those who did not receive RBC transfusions or received only one transfusion. This difference was also observed between patients who received only one RBC transfusion and those who did not receive any transfusions (p < 0.00001). Comparison of LDH levels on admission and peak LDH levels among patients in groups A, B and C revealed that 28/32 patients in group A, 56/73 patients in group B and 33/62 patients in group C had a stable LDH level, suggesting that patients with a stable LDH level require fewer RBC transfusions (p ≤ 0.006). Finally, we evaluated the possibility of an association between peak LDH levels and the degree of renal disease. The median peak LDH level in patients of group 1, 2 and 3 was 3538 (range 756-9373), 5165 (451-9205) and 7510 (1,145-16,340) U/l, respectively. Patients with >10 days of dialysis (group 3) had the highest LDH levels, followed by patients with 1-10 days of dialysis (group 2) and then by patients with no dialysis requirements (group 1) (p < 0.00001).

CONCLUSIONS

The rate of RBC transfusion was higher in patients with the most severe renal injury, and most were performed during the first 2 weeks of the disease. Patients with stable LDH levels seemed to require fewer RBC transfusions. Median peak LDH levels were significantly higher in the group of patients with the most severe renal disease.

Early erythropoietin in post-diarrheal hemolytic uremic syndrome: a case-control study

BACKGROUND

Although erythropoietin (EPO) deficiency has been reported in children with post-diarrheal hemolytic uremic syndrome (D + HUS), very limited clinical data on EPO use in this disease are currently available. In this case-control study we examined whether EPO administration would reduce the number of red blood cell (RBC) transfusions in D + HUS patients under our care.

METHODS

Data from children treated exclusively with RBC transfusions (controls; n = 21) were retrospectively compared with data on those who also received EPO for the treatment of anemia (cases; n = 21).

RESULTS

Both patient groups were similar in age (p = 0.9), gender (p = 0.12), weight (p = 1.00) and height (p = 0.66). Acute phase severity was also comparable, as inferred by the need for dialysis (p = 0.74), the duration of dialysis (p = 0.3), length of hospitalization (p = 0.81), presence of severe bowel (p = 1.00) or neurological injury (p = 0.69), arterial hypertension (p = 1.00) and death (p = 1.00). No differences in the hemoglobin level at admission (p = 0.51) and discharge (p = 0.28) were noted. Three children treated with EPO and two controls did not require any RBC transfusion (p = 1.00). Median number of RBC transfusions needed by cases and controls was 2 (p = 0.52).

CONCLUSION

Treatment with EPO did not reduce the number of RBC transfusions in D + HUS children. Assessment of EPO efficacy in D + HUS merits further studies.

Towards nano-diagnostics for bacterial infections

Sensitive, specific and rapid diagnosis of infectious diseases is essential for effective and economic medical care. Focused medical treatment of the patient enabled by pathogen-specific diagnosis may benefit the patient, may reduce cost, and may minimize the risk of drug resistance development. The rapid progress in micro and nanotechnologies contributes to the development of novel diagnostic methods. This critical review assesses emerging nanotechnologies for diagnosis of bacterial infection in developed and developing countries on the background of the current state of the art and includes particular challenges and pitfalls posed by a number of specific pathogens.

Serogroup-specific bacterial engineered glycoproteins as novel antigenic targets for diagnosis of shiga toxin-producing-escherichia coli-associated hemolytic-uremic syndrome

Human infection with Shiga toxin-producing Escherichia coli (STEC) is a major cause of postdiarrheal hemolytic-uremic syndrome (HUS), a life-threatening condition characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. E. coli O157:H7 is the dominant STEC serotype associated with HUS worldwide, although non-O157 STEC serogroups can cause a similar disease. The detection of anti-O157 E. coli lipopolysaccharide (LPS) antibodies in combination with stool culture and detection of free fecal Shiga toxin considerably improves the diagnosis of STEC infections. In the present study, we exploited a bacterial glycoengineering technology to develop recombinant glycoproteins consisting of the O157, O145, or O121 polysaccharide attached to a carrier protein as serogroup-specific antigens for the serological diagnosis of STEC-associated HUS. Our results demonstrate that using these antigens in indirect ELISAs (glyco-iELISAs), it is possible to clearly discriminate between STEC O157-, O145-, and O121-infected patients and healthy children, as well as to confirm the diagnosis in HUS patients for whom the classical diagnostic procedures failed. Interestingly, a specific IgM response was detected in almost all the analyzed samples, indicating that it is possible to detect the infection in the early stages of the disease. Additionally, in all the culture-positive HUS patients, the serotype identified by glyco-iELISAs was in accordance with the serotype of the isolated strain, indicating that these antigens are valuable not only for diagnosing HUS caused by the O157, O145, and O121 serogroups but also for serotyping and guiding the subsequent steps to confirm diagnosis.

Laboratory predictors of acute dialysis in hemolytic uremic syndrome

BACKGROUND

Strict guidelines on use of dialysis in children with post-diarrheal hemolytic uremic syndrome (D + HUS) are lacking. This study investigated laboratory predictors of acute dialysis because they are more objective than clinical features. Added to this, given that urine output is also an objective parameter, its ability to predict dialysis requirements was also investigated.

METHODS

Out of 153 D + HUS children reviewed, 88 received dialysis and 65 did not. Initial laboratory parameters and diuresis between both groups were analyzed.

RESULTS

Dialyzed patients had higher creatinine, urea, alanine aminotransferase, hematocrit and leukocyte count; and lower sodium, bicarbonate, and pH compared to non-dialyzed ones. Serum creatinine was the only independent predictor (P = 0.003) of dialysis; therefore, its ability to predict dialysis was estimated on receiver operating characteristic (ROC) curve analysis and using the Acute Kidney Injury Network (AKIN) staging system. Area under the ROC curve was 0.92 (95% confidence interval [95%CI]: 0.83-1) with a creatinine cut-off of 1.25 mg/dL (sensitivity, 100%; specificity, 76.5%) for children <1 year, and 0.93 (95%CI: 0.88-0.98) with a threshold of 2 mg/dL (sensitivity, 91%; specificity, 87.5%) for older children. AKIN stage 3 at admission predicted dialysis with a sensitivity of 92% and specificity of 84.2%. Urine output had the highest accuracy for dialysis prediction (sensitivity, 100%; specificity, 95.3%).

CONCLUSIONS

Initial serum creatinine concentration was the best laboratory predictor of dialysis, but the first 24 h diuresis was even better for this purpose. But, given that serum creatinine is an immediate available parameter, the cut-offs identified may label D + HUS children who will probably need dialysis, prompting early referral to centers able to provide dialysis.

Genotypic characterization of Escherichia coli O157:H7 strains that cause diarrhea and hemolytic uremic syndrome in Neuquén, Argentina

Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens associated with cases of diarrhea, hemorrhagic colitis and hemolytic uremic syndrome (HUS). E. coli O157:H7 is the dominant serotype in Argentina and also in Neuquén Province, in which HUS incidence is above the national average, with a maximum of 28.6 cases per 100,000 children less than 5 years old reported in 1998. The aim of this study was to characterize a collection of 70 STEC O157 strains isolated from patients with diarrhea and HUS treated in the province of Neuquén, Argentina, between 1998 and 2011. All strains harbored eae, ehxA, rfbO157, and fliCH7 genes, and stx2a/stx2c (78.7%) was the predominant genotype. A total of 64 (91.4%) STEC O157 strains belonged to the hypervirulent clade 8 tested using both 4 and 32 SNP typing schemes. The strains showed the highest values reported in the literature for 6 of the 7 virulence determinants described in the TW14359 O157 strain associated with the raw spinach outbreak in the U.S. in 2006. Clade 8 strains were strongly associated with two of them: ECSP_3286, factor encoding an outer membrane protein that facilitates the transport of the heme complex (P=0.001), and in particular extracellular factor ECSP_2870/2872, coding proteins related to adaptation to plant hosts (P=0.000004). The q933 allele, which has been related to high toxin production, was present in 97.1% of the strains studied for the anti-terminator Q gene. In summary, this study describes, for the first time in Argentina, the almost exclusive circulation of strains belonging to the hypervirulent clade 8, and also the presence of putative virulence factors in higher frequencies than those reported worldwide. These data may help to understand the causes of the particular epidemiological situation related to HUS in Neuquén Province.

Effects of Escherichia coli subtilase cytotoxin and Shiga toxin 2 on primary cultures of human renal tubular epithelial cells

Shiga toxin (Stx)-producing Escherichia coli (STEC) cause post-diarrhea Hemolytic Uremic Syndrome (HUS), which is the most common cause of acute renal failure in children in many parts of the world. Several non-O157 STEC strains also produce Subtilase cytotoxin (SubAB) that may contribute to HUS pathogenesis. The aim of the present work was to examine the cytotoxic effects of SubAB on primary cultures of human cortical renal tubular epithelial cells (HRTEC) and compare its effects with those produced by Shiga toxin type 2 (Stx2), in order to evaluate their contribution to renal injury in HUS. For this purpose, cell viability, proliferation rate, and apoptosis were assayed on HRTEC incubated with SubAB and/or Stx2 toxins. SubAB significantly reduced cell viability and cell proliferation rate, as well as stimulating cell apoptosis in HRTEC cultures in a time dependent manner. However, HRTEC cultures were significantly more sensitive to the cytotoxic effects of Stx2 than those produced by SubAB. No synergism was observed when HRTEC were co-incubated with both SubAB and Stx2. When HRTEC were incubated with the inactive SubA_A272B toxin, results were similar to those in untreated control cells. Similar stimulation of apoptosis was observed in Vero cells incubated with SubAB or/and Stx2, compared to HRTEC. In conclusion, primary cultures of HRTEC are significantly sensitive to the cytotoxic effects of SubAB, although, in a lesser extent compared to Stx2.

Long-term outcomes of Shiga toxin hemolytic uremic syndrome

Shiga toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome (HUS) is an important cause of acute kidney injury (AKI). The outcomes of STEC HUS have improved, and the acute mortality rate in children is 1-4%. About 70% of patients recover completely from the acute episode and the remainder have varying degrees of sequelae. Only a few retrospective studies have reviewed these patients over long periods. Methodological flaws include a lack of strict definitions, changing modes of treatment, ascertainment bias and loss of subjects to follow-up. The kidneys bear the brunt of the long-term damage: proteinuria (15-30% of cases); hypertension (5-15%); chronic kidney disease (CKD; 9-18%); and end-stage kidney disease (ESKD; 3%). A smaller number have extra-renal sequelae: colonic strictures, cholelithiasis, diabetes mellitus or brain injury. Most renal sequelae are minor abnormalities, such as treatable hypertension and/or variable proteinuria. Most of the patients who progress to ESKD do not recover normal renal function after the acute episode. Length of anuria (more than 10 days) and prolonged dialysis are the most important risk factors for a poor acute and long-term renal outcome. After the acute episode all patients must be followed for at least 5 years, and severely affected patients should be followed indefinitely if there is proteinuria, hypertension or a reduced glomerular filtration rate (GFR).

The Canadian contribution to the science of verotoxigenicEscherichia coliand associated illnesses: the early years

As stories of microbiological and infectious disease discoveries are told, one of the most charming of these in Canadian history is the recognition of verotoxigenic Escherichia coli (VTEC) and associated disease. The considerable burden and impact of VTEC-associated infections is currently experienced worldwide. Jack Konowalchuk, Joan Speirs, and their collaborators in Ottawa, Ontario, defined the E. coli verotoxin. Mohamed Karmali, Martin Petric, and colleagues at The Hospital for Sick Children in Toronto, Ontario, established the association of VTEC and hemolytic–uremic syndrome. Nationwide, and with the dissemination of knowledge through the central health directorate in Ottawa, numerous scientists and clinicians were motivated to focus on this theme, and within a relatively brief chronology, much became known about the biology of VTEC and the pathogenesis, epidemiology, and clinical aspects of disease. Many Canadian investigators, but especially those in the veterinary school at Guelph, Ontario, also contributed to the science of VTEC among animals. The interactions between clinical and veterinary researchers led to a then unprecedented exponential growth in the knowledge base of VTEC. Canadians also participated in a better understanding of the origin and potential of the E. coli O157 serogroup. Whereas not exclusively Canadian, the contributions of our national scientists in this field must be seen as a vital part of medical and microbiological Canadiana; this essence is captured in this historical review.

Role of TNF-α in the mechanisms responsible for preterm delivery induced by Stx2 in rats

BACKGROUND AND PURPOSE

Infections with a strain of Escherichia coli producing Shiga toxins could be one of the causes of fetal morbidity and mortality in pregnant women. We have previously reported that Shiga toxin type 2 (Stx2) induces preterm delivery in pregnant rats. In this study, we evaluate the role of TNF-α, PGs and NO in the Stx2-induced preterm delivery.

EXPERIMENTAL APPROACH

Pregnant rats were treated with Stx2 (0.7 ng g(-1)) and killed at different times after treatment. Placenta and decidua were used to analyse NOS activity by the conversion of L-[(14)C]arginine into L-[(14)C]citrulline, levels of PGE(2) and PGF(2α) assessed by radioimmunoassay, and cyclooxygenase (COX) proteins by Western blot. TNF-α level was analysed in serum by ELISA and by cytotoxicity in L929 cells. The inhibitor of inducible NOS, aminoguanidine, the COX-2 inhibitor, meloxicam, and the competitive inhibitor of TNF-α, etanercept, were used alone or combined to inhibit NO, PGs and TNF-α production respectively, to prevent Stx2-induced preterm delivery.

KEY RESULTS

Stx2 increased placental PGE(2) and decidual PGF(2α) levels as well as COX-2 expression in both tissues. Aminoguanidine and meloxicam delayed the preterm delivery time but did not prevent it. Etanercept blocked the TNF-α increase after Stx2 treatment and reduced the preterm delivery by approximately 30%. The combined action of aminoguanidine and etanercept prevented Stx2-induced preterm delivery by roughly 70%.

CONCLUSION AND IMPLICATIONS

Our results demonstrate that the increased TNF-α and NO induced by Stx2 were the predominant factors responsible for preterm delivery in rats.

Escherichia coli O157:H7-Clinical aspects and novel treatment approaches

Escherichia coli O157:H7 is a notorious pathogen often contracted by intake of contaminated water or food. Infection with this agent is associated with a broad spectrum of illness ranging from mild diarrhea and hemorrhagic colitis to the potentially fatal hemolytic uremic syndrome (HUS). Treating E. coli O157:H7 infection with antimicrobial agents is associated with an increased risk of severe sequelae such as HUS. The difficulty in treating this bacterium using conventional modalities of antimicrobial agent administration has sparked an interest in investigating new therapeutic approaches to this bacterium. These approaches have included the use of probiotic agents and natural products with variable success rates. In addition, novel modalities and regimen of antimicrobial agent administration have been assessed in an attempt at decreasing their association with aggravating infection outcomes.

Dehydration at admission increased the need for dialysis in hemolytic uremic syndrome children

BACKGROUND

Oligoanuric forms of postdiarrheal hemolytic uremic syndrome (D+ HUS) usually have more severe acute stage and higher risk of chronic sequelae than nonoligoanuric forms. During the diarrheal phase, gastrointestinal losses could lead to dehydration with pre-renal injury enhancing the risk of oligoanuric D+ HUS. Furthermore, it had been shown that intravenous volume expansion during the prodromal phase could decrease the frequency of oligoanuric renal failure. Thus, we performed this retrospective study to determine whether dehydration on admission is associated with increased need for dialysis in D+ HUS patients.

CASE-DIAGNOSIS/TREATMENT

Data from 137 children was reviewed, which were divided into two groups according to their hydration status at admission: normohydrated (n = 86) and dehydrated (n = 51). Laboratory parameters of the dehydrated patients reflected expected deteriorations (higher urea, higher hematocrit and lower sodium, bicarbonate, and pH) than normohydrated ones. Likewise, the dehydrated group had a higher rate of vomiting and need for dialysis (70.6 versus 40.7 %, p = 0.0007).

CONCLUSIONS

Our data suggests that dehydration at hospital admission might represent a concomitant factor aggravating the intrinsic renal disease in D+ HUS patients increasing the need for dialysis. Therefore, the early recognition of patients at risk of D+ HUS is encouraged to guarantee a well-hydrated status.

Acute dialysis-associated peritonitis in children with D+ hemolytic uremic syndrome

Acute peritoneal dialysis (PD) is the preferred therapy for renal replacement in children with post-diarrheal hemolytic uremic syndrome (D+ HUS), but peritonitis remains a frequent complication of this procedure. We reviewed data from 149 patients with D+ HUS who had undergone acute PD with the aim of determining the prevalence and risk factors for the development of peritonitis. A total of 36 patients (24.2%) presented peritonitis. The median onset of peritonitis manifestations was 6 (range 2-18) days after the initiation of dialysis treatment, and Gram-positive microorganisms were the predominant bacterial type isolated (15/36 patients). The patients were divided into two groups: with or without peritonitis, respectively. Univariate analysis revealed that a longer duration of the oligoanuric period, more days of dialysis, catheter replacement, stay in the intensive care unit, and hypoalbuminemia were significantly associated to the development of peritonitis. The multivariate analysis, controlled by duration of PD, identified the following independent risk factors for peritonitis: catheter replacement [p = 0.037, odds ratio (OR) 1.33, 95% confidence interval (CI) 1.02-1.73], stay in intensive care unit (p = 0.0001, OR 2.62, 95% CI 1.65-4.19), and hypoalbuminemia (p = 0.0076, OR 1.45, 95% CI 1.10-1.91). Based on these findings, we conclude that the optimization of the aseptic technique during catheter manipulation and early nutritional support are targets for the prevention of peritonitis, especially in critically ill patients.

Hemorrhagic colitis in postdiarrheal hemolytic uremic syndrome: retrospective analysis of 54 children

Hemorrhagic colitis (HC) is a severe manifestation of the hemolytic uremic syndrome (HUS). We performed a retrospective analysis of patients with HC with the following aims: (1) to characterize the clinicopathologic features; (2) to evaluate mortality rate; (3) to analyze severity of renal and central nervous system (CNS) disease. Patients with HC assisted between 1981-2009 were evaluated and compared with a control group of 137 patients without HC. Among 987 patients with diarrheal prodrome (D) + HUS, 54 (5.5%) presented HC. Clinical findings included abdominal pain (96%), distension (93%), hematochezia (44%), and abdominal mass (11%). Surgery was indicated in 35 patients (65%), and 17 (48.5%) required bowel resection. Transverse and ascending colon were most frequently affected. Macroscopic evaluation showed bowel necrosis (18) and perforation (12). Histologic evaluation (29) showed that 25 (86.2%) had necrosis of the affected segment (transmural in 21). A leukocyte count >20,000/mm(3) and hematocrit >30% were more common in HC patients than in controls (p < 0.001 and p < 0.0001, respectively). Mortality rate was higher in HC patients (33.3%) than in controls (1.4%; p < 0.0001). Dialysis >10 days, seizures, and coma were more frequent in HC patients than in controls (p < 0.0001). In summary, most patients had prominent abdominal findings, and almost 2/3 patients required surgery. Transverse/ascending colon was most affected, and the main histologic finding was transmural necrosis. Higher hematocrit and leukocytosis were frequent. Mortality rate was extremely high, and most had long-lasting anuria and severe neurologic involvement.

Effect of diet, enalapril, or losartan in post-diarrheal hemolytic uremic syndrome nephropathy

Proteinuria is the main indicator of renal disease progression in many chronic conditions. There is currently little information available on the efficacy, safety, and individual tolerance of patients with post-diarrheal hemolytic uremic syndrome (D+ HUS) nephropathy to therapies involving diet, enalapril, or losartan. A multicenter, double-blind, randomized controlled trail was conducted to evaluate the effect of a normosodic-normoproteic diet (Phase I) and the effect of normosodic-normoproteic diet plus enalapril (0.18-0.27 mg/kg/day) or losartan (0.89-1.34 mg/kg/day) (Phase II) on children with D+ HUS, normal renal function, and persistent, mild (5.1-49.9 mg/kg/day) proteinuria. Dietary intervention reduced the mean protein intake from 3.4 to 2.2 mg/kg/day. Of 137 children, proteinuria normalized in 91 (66.4 %) within 23-45 days; the remaining 46 patients were randomized to diet plus placebo (group 1, n = 16), plus losartan (group 2, n = 16), or enalapril (group 3, n = 14). In groups 1, 2, and 3, proteinuria was reduced by 30.0, 82.0, and 66.3%, respectively, and normalized in six (37.5%), three (81.3%), and 11 (78.6%) patients, respectively (χ(2)= 8.9, p = 0.015). These results suggest that: (1) a normosodic-normoproteic diet can normalize proteinuria in the majority of children with D+ HUS with mild sequelae, (2) the addition of enalapril or losartan to such dietary restrictions of protein further reduces proteinuria, and (3) these therapeutic interventions are safe and well tolerated. Whether these short-term effects can be extended to the long-term remains to be demonstrated.

A glucosylceramide synthase inhibitor protects rats against the cytotoxic effects of shiga toxin 2

Postdiarrhea hemolytic uremic syndrome is the most common cause of acute renal failure in children in Argentina. Renal damage has been strongly associated with Shiga toxin (Stx), which binds to the globotriaosylceramide (Gb3) receptor on the plasma membrane of target cells. The purpose of the study was to evaluate the in vivo effects of C-9, a potent inhibitor of glucosylceramide synthase and Gb3 synthesis, on kidney and colon in an experimental model of hemolytic uremic syndrome in rats. Rats were i.p. injected with supernatant from recombinant Escherichia coli expressing Stx2 (sStx2). A group of these rats were orally treated with C-9 during 6 d, from 2 d prior until 4 d after sStx2 injection. The injection of sStx2 caused renal damage as well as a loss of goblet cells in colonic mucosa. Oral treatment with C-9 significantly decreased rat mortality to 50% and reduced the extension of renal and intestinal injuries in the surviving rats. The C-9 also decreased Gb3 and glucosylceramide expression levels in rat kidneys. It is particularly interesting that an improvement was seen when C-9 was administered 2 d before challenge, which makes it potentially useful for prophylaxis.

Levels of urinary transforming growth factor beta-1 in children with D+ hemolytic uremic syndrome

About 25-50% of survivors of the acute phase of postdiarrheal hemolytic uremic syndrome (D+ HUS) develop chronic renal disease. Transforming growth factor beta-1 (TGFbeta-1) is the main fibrogenic growth factor in humans, and there is a significant correlation between its levels and the grade of interstitial fibrosis in chronic nephropathies. We hypothesized that increased urinary TGFbeta-1 may be an early indicator of sequelae in D+ HUS patients who show no sign of renal damage as determined by conventional diagnostic tests. We therefore compared the levels of TGFbeta-1 in urine collected from healthy controls (HC) (n = 18) with that from patients with a past history of D+ HUS (n = 39). We found that TGFbeta-1 excretion was significantly higher (p < 0.001) in the patient group (median level 73 pg/mg creatinine) than in the HC (median level 28 pg/mg creatinine). TGFbeta-1 excretion did not correlate with age, white blood cell count, length of oligoanuric period, maximum creatinine at the acute stage, or length of the follow-up. Since TGFbeta-1 excretion may reflect ongoing renal tissue damage, our results emphasize the need for the lifelong follow-up of patients with a past history of D+ HUS, even those showing apparent recovery. Long-term monitoring of this cohort is necessary to determine the clinical utility of our findings.

Hemolytic uremic syndrome: pathogenesis and update of interventions

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

Familial occurrence of the haemolytic uraemic syndrome

A family is described in which the haemolytic uraemic syndrome (HUS) occurred in two generations. Both juvenile and adult onset of this syndrome were observed in this family. Those affected were all women, three developed HUS in the postpartum period, one towards the end of pregnancy and one as a five-year old child. Because five cases were observed over a period of 16 years, exposure to the same infectious agent is highly unlikely. Although the transmission of a "dormant" virus cannot be excluded, the occurrence of HUS in two generations of one and the same family seems compatible with the hypothesis that susceptibility to the disease is transmitted as an autosomal dominant characteristic. This observation suggests a genetic influence on the development of HUS, possibly in conjunction with other factors, such as infectious agents, pregnancy and/or delivery.

Inhibition of water absorption in human proximal tubular epithelial cells in response to Shiga toxin-2

Postdiarrhea hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children in Argentina. It is well established that Shiga toxin type 2 (Stx2) causes direct damage to glomerular endothelial cells and tubular epithelial cells, leading to a reduction in the water handling capacity of the kidney. In this study, we demonstrate that Stx2 and its B subunit (Stx2B) were able to inhibit water absorption across human renal tubular epithelial cell (HRTEC) monolayers without altering the short circuit current and the (3)H-mannitol permeability. Quantitative evaluation of (14)C-inulin transport across HRTEC monolayers showed a similar transport rate both before and after HRTEC treatment with Stx2 that confirmed the integrity of the paracellular pathway. Furthermore, Stx2 produced significant protein synthesis inhibition of HRTEC at concentrations as low as 0.001 ng/ml and 1 h of incubation, whereas Stx2B did not modify it at concentrations as high as 10,000 ng/ml and 6 h of incubation. Our findings suggest that whereas the action of Stx2 appears to be caused mainly by the inhibition of protein synthesis mediated by the A subunit, the binding of Stx2B subunit to the Gb3 receptor may affect the membrane mechanisms related to water absorption. We speculate that inhibition of water absorption may occur in proximal tubular cells in vivo in response to Stx2 and may contribute to the early event of HUS pathogenesis.

Risk factors for sporadic Shiga toxin-producing Escherichia coli infections in children, Argentina

We evaluated risk factors for sporadic Shiga toxin-producing Escherichia coli (STEC) infection among children in Argentina. We conducted a prospective case-control study in 2 sites and enrolled 150 case-patients and 299 controls. The median age of case-patients was 1.8 years; 58% were girls. Serotype O157:H7 was the most commonly isolated STEC. Exposures associated with infection included eating undercooked beef, living in or visiting a place with farm animals, and contact with a child <5 years of age with diarrhea. Protective factors included the respondent reporting that he or she always washed hands after handling raw beef and the child eating more than the median number of fruits and vegetables. Many STEC infections in children could be prevented by avoiding consumption of undercooked beef, limiting exposure to farm animals and their environment, not being exposed to children with diarrhea, and washing hands after handling raw beef.

Long-term follow-up of Argentinean patients with hemolytic uremic syndrome who had not undergone dialysis

We examined the records of patients with hemolytic uremic syndrome, who had not undergone dialysis during the acute stage, with the aims of evaluating: (1) the outcome after at least 5 years of follow-up; (2) the value of peak serum creatinine as a prognostic marker; (3) the relationship between outcome and time to normalization of renal function. From 1968 to 2000, 1,179 patients were assisted. Forty-two patients (3.6%) died during the acute stage, 478 patients (40.5%) required dialysis and 659 patients (55.9%) did not undergo dialysis; 529 non-dialysis patients were lost to follow-up. The remaining 130 patients were classified into four groups: group I, complete recovery; group II, with two subgroups, IIa, microalbuminuria, and IIb, proteinuria and/or high blood pressure, both with normal renal function; group III, chronic renal failure; and group IV, end-stage renal disease. We analyzed the relationship between final outcome and: (1) peak creatinine (the highest of at least two determinations) during the acute stage and (2) time to normalization of urea and/or creatinine after the acute stage. After a mean follow-up time of 147.1 months (range 60-362 months), group I had 83 patients (63.9%), group IIa had 27 (20.8%), group IIb had 15 (11.5%) and group III had 5 (3.8%). The value of peak serum creatinine concentration was available for 57 patients. On the last clinical visit, eight out of 26 (30.7%) patients with peak serum creatinine equal to or higher than 1.5 mg/dl were in groups IIb and III versus one out of 31 (3.2%) patients with lower values (P < or = 0.007). Finally, six out of 28 patients (21%) whose renal function had normalized after 15 days from diagnosis were in groups IIb-III versus 8/82 (9.7%) whose renal function had normalized within 15 days (P = 0.18). After a mean period of follow-up of 12 years, 15% of a selected patient group had developed proteinuria, high blood pressure or chronic renal failure, and 21% had developed microalbuminuria. Peak serum creatinine during the acute stage was useful as a prognostic indicator. Patients whose renal function required more time to normalize did not have a worse outcome.

Shiga toxin-producing Escherichia coli isolated from patients with diarrhoea in Bangladesh

The prevalence of Shiga toxin-producing Escherichia coli (STEC) and its characteristics were determined among hospitalized patients with diarrhoea and children with diarrhoea in an urban slum community of Dhaka city using sensitive culture and PCR methods. Stool samples were collected from 410 patients with diarrhoea enrolled in the 2% surveillance system (every 50th patient attending the hospital with diarrhoeal disease is included) at the ICDDR,B hospital and from 160 children of 2-5 years of age with diarrhoea living in an urban slum in Dhaka, between September 2004 and April 2005. Shiga toxin genes (stx) were detected by multiplex PCR in the enrichment broth of nine samples (2.2%) from hospitalized patients and 11 samples (6.9%) from the community patients. STEC was isolated from five stool samples with positive PCR results using a colony patch technique. All five isolates were positive in the Vero cell assay and PCR fragments of stx genes were confirmed by sequencing. Two isolates were positive for the E. coli attaching-and-effacing (eae) gene and four were positive for the enterohaemolysin (hlyEHEC) gene and enterohaemolysin production. The five isolates belonged to five different serotypes:O32:H25, O2:H45, O76:H19, ONT:H25 and ONT:H19. It can be concluded that STEC is not a common pathogen in Bangladesh among hospitalized patients with diarrhoea nor among mild cases of diarrhoea in the community.

Troponin I levels in a hemolytic uremic syndrome patient with severe cardiac failure

Troponins are highly sensitive and specific biochemical markers of myocardial injury that are released into the circulation during myocardial ischemia. We describe changes in cardiac troponin I (cTnI) prior to and following clinical evidence of severe myocardial dysfunction in a child with hemolytic uremic syndrome (HUS). A previously healthy, 22-month-old girl presented with typical HUS and stool cultures positive for Escherichia coli O157:H7. She required dialysis, blood and platelet transfusions, and insulin for HUS-related diabetes mellitus. On the 6th hospital day she had sudden circulatory collapse with a blood pressure of 70/40 mmHg and an oxygen saturation of 88%. She responded rapidly to emergency resuscitation but had diminished left ventricular function (ejection fraction 18%). Four days after the acute event an echocardiogram showed normal ventricular size and contractility. She underwent hemodialysis for 22 days, and renal function was normal after 33 days. cTnI levels were measured with a microparticle enzyme immunoassay. cTnI was normal (>0.4 microg/l) 32 h prior to cardiac collapse, mildly increased (2.1 microg/l) 8 h before the cardiac collapse, severely elevated shortly after the cardiac event (43.1 microg/l), and peaked (140.6 microg/l) at 24 h. It then fell gradually and was normal at discharge. These results suggest that measurement of cTnI may be a useful predictor of cardiac involvement in severely affected children with HUS.

Shiga toxin 2 induces macrophage-granulocyte colonies from human bone marrow and cord blood stem cells

Addition of Shiga toxin 2 to human bone marrow or cord blood cell culture induced macrophage-granulocyte colonies. Although Shiga toxin 2 alone induced colonies mainly composed of macrophages, it induced colonies mainly consisting of granulocytes when combined with physiological doses of interleukin-1beta, granulocyte colony-stimulating factor, or stem cell factor with interleukin-3.