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

ISTH guidelines for the diagnosis of thrombotic thrombocytopenic purpura

BACKGROUND

Despite an increase in our understandings of pathogenesis of thrombotic thrombocytopenic purpura (TTP), the approaches for initial diagnosis and management of TTP vary significantly.

OBJECTIVE

The evidence-based guidelines of the International Society on Thrombosis and Haemostasis (ISTH) are intended to support patients, clinicians, and other health care professionals in their decisions about the initial diagnosis and management of acute TTP.

METHODS

In June 2018, ISTH formed a multidisciplinary panel that included hematologists, an intensive care physician, nephrologist, clinical pathologist, biostatistician, and patient representatives, as well as a methodology team from McMaster University. The panel composition was designed to minimize the potential conflicts of interests. The panel used the Grading of Recommendations Assessment, Development, and Evaluation approach and the Population, Intervention, Comparison, Outcome framework to develop and grade their recommendations. Public comments were sought and incorporated in the final document.

RESULTS

The panel agreed on three recommendations covering the initial diagnosis with emphasis on the importance of ADAMTS13 testing (eg, activity, anti-ADAMTS13 IgG or inhibitor) and assessment of the pretest probability of TTP by clinical assessment and/or the risk assessment models like the PLASMIC or French score. The panel noted how availability and turnaround time of ADAMTS13 test results might affect early diagnosis and management, in particular the use of caplacizumab.

CONCLUSIONS

There is a lack of high-quality evidence to support strong recommendations for the initial diagnosis and management of a suspected TTP. The panel emphasized the importance of obtaining ADAMTS13 testing in a proper clinical context. Future research should focus on how to monitor and act on ADAMTS13 levels during remission.

Postinfectious Hemolytic Uremic Syndrome

Post-infectious hemolytic uremic syndrome (HUS) is caused by specific pathogens in patients with no identifiable HUS-associated genetic mutation or autoantibody. The majority of episodes is due to infections by Shiga toxin (Stx) producing Escherichia coli (STEC). This chapter reviews the epidemiology and pathogenesis of STEC-HUS, including bacterial-derived factors and host responses. STEC disease is characterized by hematological (microangiopathic hemolytic anemia), renal (acute kidney injury) and extrarenal organ involvement. Clinicians should always strive for an etiological diagnosis through the microbiological or molecular identification of Stx-producing bacteria and Stx or, if negative, serological assays. Treatment of STEC-HUS is supportive; more investigations are needed to evaluate the efficacy of putative preventive and therapeutic measures, such as non-phage-inducing antibiotics, volume expansion and anti-complement agents. The outcome of STEC-HUS is generally favorable, but chronic kidney disease, permanent extrarenal, mainly cerebral complication and death (in less than 5 %) occur and long-term follow-up is recommended. The remainder of this chapter highlights rarer forms of (post-infectious) HUS due to S. dysenteriae, S. pneumoniae, influenza A and HIV and discusses potential interactions between these pathogens and the complement system.

Contributions of EspA Filaments and Curli Fimbriae in Cellular Adherence and Biofilm Formation of Enterohemorrhagic Escherichia coli O157:H7

In Escherichia coli O157:H7 (O157), the filamentous structure of the type III secretion system is produced from the polymerization of the EspA protein. EspA filaments are essential for O157 adherence to epithelial cells. In previous studies, we demonstrated that O157 hha deletion mutants showed increased adherence to HEp-2 cells and produced abundant biofilms. Transcriptional analysis revealed increased expression of espA as well as the csgA gene, which encodes curli fimbriae that are essential for biofilm formation. In the present study, we constructed hha espA, hha csgA, and hha csgA espA deletion mutants to determine the relative importance of EspA and CsgA in O157 adherence to HEp-2 cells and biofilm formation. In vitro adherence assays, conducted at 37°C in a tissue culture medium containing 0.1% glucose, showed that HEp-2 cell adherence required EspA because hha espA and hha csgA espA mutants adhered to HEp-2 cells at higher levels only when complemented with an espA-expressing plasmid. Biofilm assays performed at 28°C in a medium lacking glucose showed dependency of biofilm formation on CsgA; however EspA was not produced under these conditions. Despite production of detectable levels of EspA at 37°C in media supplemented with 0.1% glucose, the biofilm formation occurred independent of EspA. These results indicate dependency of O157 adherence to epithelial cells on EspA filaments, while CsgA promoted biofilm formation under conditions mimicking those found in the environment (low temperature with nutrient limitations) and in the digestive tract of an host animal (higher temperature and low levels of glucose).

Effects of Mycotoxins on mucosal microbial infection and related pathogenesis

Mycotoxins are fungal secondary metabolites detected in many agricultural commodities and water-damaged indoor environments. Susceptibility to mucosal infectious diseases is closely associated with immune dysfunction caused by mycotoxin exposure in humans and other animals. Many mycotoxins suppress immune function by decreasing the proliferation of activated lymphocytes, impairing phagocytic function of macrophages, and suppressing cytokine production, but some induce hypersensitive responses in different dose regimes. The present review describes various mycotoxin responses to infectious pathogens that trigger mucosa-associated diseases in the gastrointestinal and respiratory tracts of humans and other animals. In particular, it focuses on the effects of mycotoxin exposure on invasion, pathogen clearance, the production of cytokines and immunoglobulins, and the prognostic implications of interactions between infectious pathogens and mycotoxin exposure.

Chronic sequelae of E. coli O157: systematic review and meta-analysis of the proportion of E. coli O157 cases that develop chronic sequelae

OBJECTIVE

This was a systematic review and meta-analysis to determine the proportion of Escherichia coli O157 cases that develop chronic sequelae.

DATA SOURCES

We conducted a systematic review of articles published prior to July 2011 in Pubmed, Agricola, CabDirect, or Food Safety and Technology Abstracts.

STUDY SELECTION

Studies were selected that reported the number of E. coli O157 cases that developed reactive arthritis (ReA), hemolytic uremic syndrome (HUS), irritable bowel syndrome, inflammatory bowel disease, or Guillain Barré syndrome.

METHODS

Three levels of screening and data extraction of articles were conducted using predefined data fields. Meta-analysis was performed on unique outcome measures using a random-effects model, and heterogeneity was assessed using the I² value. Meta-regression was used to explore the influence of nine study-level variables on heterogeneity.

RESULTS

A total of 82 studies were identified reporting 141 different outcome measures; 81 reported on HUS and one reported on ReA. Depending on the number of cases of E. coli O157, the estimate for the proportion of E. coli O157 cases that develop HUS ranged from 17.2% in extra-small studies (<50 cases) to 4.2% in extra-large studies (>1000 cases). Heterogeneity was significantly associated with group size (p<0.0001); however, the majority of the heterogeneity was unexplained.

CONCLUSIONS

High unexplained heterogeneity indicated that the study-level factors examined had a minimal influence on the variation of estimates reported.

Experiences with HUS in Canada: what have we learned about childhood HUS in Canada?

Experiences with childhood hemolytic uremic syndrome (HUS) in Canada will focus on the development of the Canadian Pediatric Kidney Disease Research Centre (CPKDRC) and the results of our collaborative research over a 13-year period (1985-1998).

Liposome-based microcapillary immunosensor for detection of Escherichia coli O157:H7

Our group has previously reported a sandwich-based strip immunoassay for rapid detection of Escherichia coli O157:H7 [Anal. Chem. 75 (2003) 4330]. In the present study, a microcapillary flow injection liposome immunoanalysis (mFILIA) system was developed for the detection of heat-killed E. coli O157:H7. A fused-silica microcapillary with anti-E. coli O157:H7 antibodies chemically immobilized on the internal surface via protein A served as an immunoreactor/immunoseparator for the mFILIA system. Liposomes tagged with anti-E. coli O157:H7 and encapsulating a fluorescent dye were used as the detectable label. In the presence of E. coli O157:H7, sandwich complexes were formed between the immobilized antibodies in the column, the sample of E. coli O157:H7 and the antibody-tagged sulforhodamine-dye-loaded liposomes. Signals generated by lysing the bound liposomes with 30 mM n-octyl-beta-D-glucopyranoside were measured by a fluorometer. The detected signal was directly proportional to the amount of E. coli O157:H7 in the test sample. The mFILIA system successfully detected as low as 360 cells/mL (equivalent to 53 heat-killed bacteria in the 150 microL of the sample solution injected). MeOH (30%) was used for the regeneration of antibody binding sites in the capillary after each measurement, which allowed the immunoreactor/immunoseparator to be used for at least 50 repeated assays. The calibration curve for heat-killed E. coli O157:H7 has a working range of 6 x 10(3)-6 x 10(7)cells, and the total assay time was less than 45 min. A coefficient of variation for triplicate measurements was < or =8.9%, which indicates an acceptable level of reproducibility for this newly developed method.

Detection of Escherichia coli O157:H7 using immunomagnetic separation and absorbance measurement

An assay system for detection of Escherichia coli O157:H7 was developed based on immunomagnetic separation of the target pathogen from samples and absorbance measurement of p-nitrophenol at 400 nm from p-nitrophenyl phosphate hydrolysis by alkaline phosphatase (EC 3.1.3.1) on the "sandwich" structure complexes (antibodies coated onto micromagnetic beads--E. coli O157:H7-antibodies conjugated with the enzyme) formed on the microbead surface. The effects of immunoreaction time, phosphate buffer concentration, pH and temperature on the immunomagnetic separation of E. coli O157:H7 from samples were determined and the conditions used for the separation were 1-h reaction time, 1.0 x 10(-2) M PBS, pH 8.0 and 33 degrees C in this system. The effects of MgCl(2) concentration, Tris buffer concentration, pH and temperature on the activity of alkaline phosphatase conjugated on the immuno-"sandwich" structure complexes were investigated after immunomagnetic separation of the target pathogen and the conditions used for the enzymatic amplification were 1.0 x 10(-4) M MgCl(2), 1.0 M Tris buffer, pH 8.0, 28 degrees C and 30-min reaction time during the assay. The selectivity of the system was examined and no interference from the other pathogens including Salmonella typhimurium, Campylobacter jejuni and Listeria monocytogenes was observed. Its working range was from 3.2 x 10(2) to 3.2 x 10(4) CFU/ml, and the relative standard deviation was 2.5-9.9%. The total detection time was less than 2 h.

Verotoxigenic Escherichia coli (VTEC): a major public health threat in Canada

BACKGROUND

Verotoxigenic Escherichia coli (VTEC) was first described in Canada during the 1980s as an emerging foodborne disease in association with morbidity and mortality in outbreaks of hemorrhagic colitis caused by E coli O157:H7.

OBJECTIVE

To describe the surveillance activities and epidemiological laboratory markers of VTEC that are used at the National Laboratory for Enteric Pathogens (NLEP) to investigate sporadic cases and outbreaks of E coli O157:H7 and non-O157 VTEC in Canada.

METHODS

Passive surveillance was conducted by obtaining data on laboratory confirmed cases of VTEC from the Provincial Laboratories of Public Health across Canada. The laboratory epidemiological markers generated for isolates of VTEC included biotyping, serotyping, phage typing, toxin detection and characterization, and molecular typing using pulsed-field gel electrophoresis.

RESULTS

Major outbreaks of VTEC O157:H7 disease have been associated with ground beef, unpasteurized apple juice, salami and untreated water. In 1999 and 2000, a total of 46 outbreaks of E coli O157:H7 disease were investigated. Among those, one outbreak was associated with contact at a petting zoo and a second with the consumption of salami. An outbreak in 2000 in Ontario was associated with water and resulted in more than 1000 cases of human illness, with six deaths. The NLEP has also identified more than 100 non-O157 VTEC serotypes from cattle and meat products. At least 23 VTEC serotypes found in humans were also identical to those found in cattle and meat products.

CONCLUSIONS

The laboratory-based information that is generated is used to define the incidence, sources of infection, risk factors, trends, distribution and transmission of VTEC to humans from food, water and animal sources. Prevention and control of outbreaks are high-priority health concerns.

Shiga toxin-producing Escherichia coli infection and antibodies against Stx2 and Stx1 in household contacts of children with enteropathic hemolytic-uremic syndrome

Ninety-five household contacts (aged 2 months to 73 years) of patients with enteropathic hemolytic-uremic syndrome (HUS) were investigated for the presence of immunoglobulin (Ig) G antibodies to Shiga toxins Stx2 and Stx1 by Western blot assay. Thirty-one percent of the household contacts and 19% of 327 controls had anti-Stx2 IgG (heavy and light chain [H + L]), 5 and 8%, respectively, had anti-Stx1 IgG (H + L), and 3 and 2%, respectively, had both anti-Stx2 and anti-Stx1 IgG (H + L). The incidence of infections with Stx-producing Escherichia coli (STEC) was determined based on the following diagnostic criteria: STEC isolation, detection of stx gene sequences, free fecal Stx in stool filtrates, and serum IgM antibodies against E. coli O157 lipopolysaccharide. Evidence of STEC infection was observed in 25 household contacts, of whom 18 (72%) were asymptomatic and represented a potential source of infection. Six of 13 (46%) household contacts with Stx2-producing E. coli O157:H7 in stool culture developed anti-Stx2 IgG (H + L), compared to 71% of Stx2-associated HUS cases. In individuals showing anti-Stx2 IgG (H + L), the antibody response was directed against the B subunit in 69% of household contacts and 71% of controls, in contrast to 28% of HUS patients. In this investigation controls had a significant increase of the median of IgM antibodies to O157 lipopolysaccharide (LPS) with age, up to the fifth decade. The lack of disease in household contacts with B subunit-specific antibodies, as well as the significantly higher median of anti-O157 LPS IgM antibodies in controls beyond 4.9 years of age, suggests a protective role for anti-Stx and anti-O157 LPS antibodies.

An antibody-immobilized capillary column as a bioseparator/bioreactor for detection of Escherichia coil O157:H7 with absorbance measurement

A capillary-column-based bioseparator/bioreactor was developed for detection of Escherichia coli O157:H7 by chemically immobilizing anti-E. coli O157:H7 antibodies onto the inner wall of the column, forming the "sandwich" immunocomplexes (immobilized antibody-E. coli O157: H7-enzyme-labeled antibody) after the sample and the enzyme-labeled antibody passed through the column and detecting the absorbance of the product in the bioreactor with an optical detector. The effects of the blocking agent, flow rate of samples and substrates, buffer, MgCl2, and pH on the detection of E. coli O157:H7 were investigated. The parameters, 2% BSA in 1.0 x 10-2 M, pH 7.4, PBS as the blocking agent, 0.5 mL/h as the sample flow rate, 1.0 x 10(-2) M MgCl2, and 2.0 x 10(-4) M p-nitrophenyl phosphate in 1.0 M, pH 9.0 Tris buffer as the substrate for the enzymatic reaction, and 1.0 mL/h as the substrate flow rate, were used in the bioseparator/bioreactor system for detection of E. coli O157:H7. The selectivity of the system was checked, and other pathogens, including Salmonella typhimurium, Campylobacterjejuni, and Listeria monocytogenes, had no interference with the detection of E. coli O157:H7. Its working range was from 5.0 x 10(2) to 5.0 x 10(6) cfu/mL, and the total assay time was < 1.5 h without any enrichment. The relative standard deviation was approximately 2.0-7.3%.

Verocytotoxin-producing Escherichia coli infection in household members of children with hemolytic-uremic syndrome in The Netherlands

BACKGROUND

Strains of verocytotoxin-producing Escherichia coli (VTEC) belonging to serogroup O157 (O157 VTEC) can cause a spectrum of disease that includes nonspecific diarrhea, hemorrhagic colitis and the diarrhea-associated form of the hemolytic uremic syndrome (D+ HUS).

METHODS

We conducted a retrospective study of 34 children with D+ HUS caused by O157 VTEC to determine the frequency of VTEC infection in their household members.

RESULTS

Gastrointestinal tract symptoms were reported in 1 or more household contacts of 17 (50%) of the 34 index cases. Of the 26 household members with gastrointestinal tract symptoms, 15 were parents and 11 were siblings. Evidence of VTEC infection was reported in 1 or more household contacts in 23 (68%) of the 34 families (in 46% of the siblings and in 28% of the parents). Nineteen (48%) siblings had a positive stool sample and in only 5 (12%) of the siblings IgM class serum antibodies to O157-lipopolysaccharide (LPS) were detected. Nineteen (31%) parents had a positive stool sample. Antibodies to O157-LPS were not detected in any of the parents. The occurrence of (bloody) diarrhea significantly correlated with the occurrence of IgM class serum antibodies to O157-LPS.

CONCLUSIONS

It was concluded that household members of children with D+ HUS are often asymptomatically infected with O157 VTEC. Differences in the pathogenesis of the infection between infected individuals may be related to differences in the number of ingested O157 VTEC bacteria and to differences in susceptibility.

Renal transplantation in adults with autosomal recessive inheritance of hemolytic uremic syndrome

When hemolytic uremic syndrome (HUS) is occasionally inherited in an autosomal recessive mode, this occurs mainly in infants and children. We describe four families in which two adult siblings were affected with HUS in each kindred. HUS first occurred between the ages of 19 to 36 years, and the intervals between the onset of HUS in each sibling pair ranged from 6 months to 6 years. None of the patients had a typical prodrome of bloody diarrhea, and one had a recurrence of HUS before transplantation. All eight patients developed renal failure requiring dialysis and transplantation, and seven patients received kidney transplants. Donor kidneys were from parents, siblings, and cadavers. The initial renal transplants were performed from 6 months to 6 years after the onset of the syndrome. HUS recurred in six of the seven patients 2 weeks to 6.5 years after transplantation regardless of the interval between the onset of HUS and transplantation, the origin of the allograft, or the use of cyclosporin A. The only marker for autosomal recessive HUS is the occurrence of the syndrome in a second sibling several months to many years after its occurrence in the proband. In patients with the autosomal recessive form of HUS, the risk for a recurrence in an allograft is high regardless of the source of the kidney.

Outbreak of Escherichia coli O157:H7 infection in a large family

An outbreak of bloody and nonbloody diarrhoea caused by Escherichia coli O157:H7 including one case of haemolytic uraemic syndrome (HUS) and two cases of haemolytic anaemia, in five siblings (aged 2.5 to 11.3 years) and their playmate was investigated. Using sorbitol-MacConkey agar, colony blot hybridisation, and immunomagnetic separation, Shiga toxin 2-producing Escherichia coli O157:H7 was isolated from all children but the HUS patient; however, this patient had high immunoglobulin M antibody titres against Escherichia coli O157 lipopolysaccharide. Escherichia coli O157 isolates from all patients were indistinguishable in serotype, virulence properties, and genomic background, indicating that the same strain caused the infections. These data confirm the importance of person-to-person transmission.

Diarrhea in young children associated with Escherichia coli non-O157 organisms that produce Shiga-like toxin

OBJECTIVE

To assess the clinical manifestations and incidence of infection associated with Shiga-like toxin-producing Escherichia coli (SLTEC).

STUDY DESIGN

Children with diarrhea within a defined geographic area during a 12-month period were examined for the presence of SLTEC in their stools by polymerase chain reaction with the use of primers that were complementary to sequences of Shiga-like toxins types I and II and to other virulence factors.

RESULTS

There were 13 SLTEC infections among 468 children with diarrhea. Besides Shiga-like toxin sequences, the virulence genes eae and EHEC-hly were found in 10 isolates; these isolates were categorized as enterohemorrhagic E. coli (EHEC). Only 2 of 13 isolates were of the O157 strain. All reported cases occurred in summer (June through September) with the exception of one case in April. The infections were sporadic, and the infected children lived in rural and urban areas. Three infections in children with disabilities were hospital acquired. The majority of children had watery diarrhea, two had bloody diarrhea, and one had mild hemolytic-uremic syndrome. The overall incidence of SLTEC infection was 12.5 hospitalized children per 100,000 children less than 16 years of age.

CONCLUSIONS

The most frequent clinical manifestation of SLTEC infection was watery diarrhea indistinguishable from other forms of infectious diarrhea. The shift from the O157 strain toward non-O157 SLTEC strains associated with diarrhea, also observed in German patients with hemolytic-uremic syndrome, points to a change in the epidemiologic features of SLTEC-associated disease. Testing for non-O157 SLTEC should be considered in children with diarrhea without a recognized cause.

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

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

A community outbreak of haemolytic-uraemic syndrome in children occurring in a large area of northern Italy over a period of several months

From March to October 1993, 15 cases of haemolytic-uraemic syndrome (HUS) in children were detected in a large area of northern Italy, where only 8 cases had occurred in the previous 5 years. Analysis of stool and serum specimens obtained from 14 cases showed evidence of Verotoxin-producing Escherichia coli (VTEC) infection in 13. Serum antibodies to the E. coli O157 lipopolysaccharide (LPS) were found in 8 patients and to the O111 LPS in 2. An O86 VTEC was isolated from another patient. Fourteen children needed dialysis, and 1 died. No obvious epidemiologic link was observed among cases, most of whom lived in small townships. A case-control study did not show an association between HUS and food or exposure to cattle, but suggested an association with contact with chicken coops (OR = 6.5, 95% C.I. 1.2-34.9). However, VTEC were not isolated from stool samples obtained from the chicken coops involved. The risk factors for VTEC infection related to living in rural settlements, including the exposure to live poultry, should be considered in outbreak investigations.

Haemolytic anaemia in association with Escherichia coli O157 infection in two sisters

Two sisters, 2 and 5 years of age, suffered from acute haemolytic anaemia occurring after gastroenteritis with Escherichia coli O157. One patient developed clinical signs of severe and acute intravascular haemolysis and sepsis. She received transfusion and antibiotic therapy. The second patient presented with mild to moderate haemolytic symptoms only. None of them developed renal impairment. In serum of both children, elevated titres of short-lived agglutinins were demonstrated in the indirect haemagglutination assay consisting of sheep erythrocytes coated with lipopolysaccharide from E. coli O157. By immunoblot analysis IgM antibodies against the O157 lipopolysaccharide were demonstrated in the acute phase sera but not in follow up sera taken 2 months after disease. On erythrocyte membranes, adsorption of microbial antigens was detected by use of a pool-immunoglobulin fluorescence test. The immunological status of both patients was normal. Complete recovery from haemolytic disease was observed without further therapy. Microbial antigens attached to the cell surface were assumed to be the pathophysiological cause of E. coli O157 associated haemolytic anaemia in two siblings.

Diarrhoea in close contacts as a risk factor for childhood haemolytic uraemic syndrome. The CPKDRC co-investigators

To determine whether the risk factors for childhood haemolytic uraemic syndrome (HUS) are similar to risk factors previously reported for Escherichia coli O 157. H7 gastroenteritis, we conducted a case-control study at eight paediatric hospitals in the summer of 1990. Thirty-four consecutive children with HUS were prospectively enrolled; all had diarrhoea and 88% had laboratory evidence of exposure to verotoxin-producing E. coli (VTEC). The 102 controls were otherwise healthy children with minor acute injuries. Parents of all subjects responded to a questionnaire about each child's exposure to various foods, methods of food preparation, sources of water, travel, and individuals with diarrhoea. Children with HUS were significantly more likely than controls to have had close contact with an individual with diarrhoea in the 2 weeks before the onset of illness (74 v. 29%, P < 0.00001; odds ratio 7.0, 95% CI 2.7-18.5). The onset of diarrhoea in the contacts occurred a median of 6 days (range, 1- > 14 days) before the onset of diarrhoea in the HUS patients. Exposure to undercooked ground meat was not significantly more common in the patients with HUS (15 v. 8%; P = 0.05). These data provide evidence consistent with person-to-person transmission of VTEC in a substantial proportion of episodes of childhood HUS.

Recent advances in understanding the pathogenesis of the hemolytic uremic syndromes

One of the requirements for an agent to cause hemolytic uremic syndrome (HUS) is its ability to injure endothelial cells. Shiga-like toxin (SLT) can do this. SLT is produced by Escherichia coli and Shigella dysenteriae serotype 1; both have been implicated as causes of typical HUS. Endothelial cells have receptors (GB3) for SLT and the toxin can inhibit eukaryotic protein synthesis, thereby causing cell death. Glomerular endothelial cell injury or death results in a decreased glomerular filtration rate and many of the perturbations seen in HUS. It is no longer certain that hemolysis is the result of a microangiopathy. Cell injury results in release of von Willebrand multimers; if these are ultra-large, thrombosis may ensue. There is also increasing evidence that neutrophils have a role in the pathogenesis of typical HUS. Streptococcus pneumoniae can also cause HUS and care must be taken to avoid giving plasma to patients with S. pneumoniae-associated HUS. There is compelling evidence that types of HUS are inherited by autosomal recessive and autosomal dominant modes. Patients with autosomal recessive HUS may have recurrent episodes. Mortality and morbidity rates are high for the inherited forms.

Isolation in Italy of a verotoxin-producing strain of Escherichia coli O157:H7 from a child with hemolytic-uraemic syndrome

Verotoxin-producing Escherichia coli O157:H7 was isolated for the first time in Italy from a child with hemolytic-uremic syndrome and his asymptomatic sister. Both parents remained asymptomatic, and neither had evidence of this infection. The source of the infection was not identified, but the children had eaten ground beef during the 15 days prior to the onset of symptoms.