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

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.

Associating sporadic, foodborne illness caused by Shiga toxin-producing Escherichia coli with specific foods: a systematic review and meta-analysis of case-control studies

Shiga toxin-producing Escherichia coli (STEC) infections are a significant public health issue, with foodborne transmission causing >1 million illnesses worldwide each year. We conducted a systematic review and meta-analysis (PROSPERO registry # CRD42017074239), to determine the relative association of different food types with sporadic illnesses caused by STEC. Searches were conducted from 01 August to 30 September 2017, using bibliographic and grey literature databases, websites and expert consultation. We identified 22 case-control studies of sporadic STEC infection in humans, from 10 countries within four World Health Organization subregions, from 1985 to 2012. We extracted data from 21 studies, for 237 individual measures in 11 food categories and across three status types (raw or undercooked, not raw and unknown). Beef was the most significant food item associated with STEC illness in the Americas and Europe, but in the Western Pacific region, chicken was most significant. These findings were not significantly moderated by the raw or cooked status of the food item, nor the publication year of the study. Data from the African, South-East Asian and Eastern Mediterranean subregions were lacking and it is unclear whether our results are relevant to these regions.

A role for fosfomycin treatment in children for prevention of haemolytic-uraemic syndrome accompanying Shiga toxin-producing Escherichia coli infection

The role of antimicrobial therapy for Shiga toxin-producing Escherichia coli (STEC) infection has not been clearly defined. A prospective study identified antibiotic use as a significant risk factor for subsequent development of haemolytic-uraemic syndrome (HUS). However, early treatment with fosfomycin, a bacteriostatic antibiotic, resulted in a significantly decreased risk of HUS. The aim of this study was to evaluate a role of fosfomycin therapy in the development of HUS in children who contracted STEC infection. The study included 118 children who contracted a STEC infection between 1997 and 2013. A pre-defined questionnaire was utilised to collect patient information regarding age, sex, presenting symptoms (fever, abdominal pain, diarrhoea and bloody stool), results of stool culture examination, initial results of white blood cell counts and C-reactive protein (CRP), use of antibiotics, the timing of introduction of antibiotics, and complications including HUS. Of the 118 patients, 64 were diagnosed with HUS and the remaining 54 did not develop HUS. Multivariate analysis showed that three independent factors (age, initial values of CRP and use of fosfomycin) were significantly associated with the occurrence of HUS; of particular note, the adjusted odds ratio for use of fosfomycin was 0.15 (95% confidence interval 0.05-0.45). Use of fosfomycin within the first 5 days of illness may decrease the development of STEC-related HUS in children.

Glycolipid binding preferences of Shiga toxin variants

The major virulence factor of Shiga toxin producing E. coli, is Shiga toxin (Stx), an AB5 toxin that consists of a ribosomal RNA-cleaving A-subunit surrounded by a pentamer of receptor-binding B subunits. The two major isoforms, Stx1 and Stx2, and Stx2 variants (Stx2a-h) significantly differ in toxicity. The exact reason for this toxicity difference is unknown, however different receptor binding preferences are speculated to play a role. Previous studies used enzyme linked immunosorbent assay (ELISA) to study binding of Stx1 and Stx2a toxoids to glycolipid receptors. Here, we studied binding of holotoxin and B-subunits of Stx1, Stx2a, Stx2b, Stx2c and Stx2d to glycolipid receptors globotriaosylceramide (Gb3) and globotetraosylceramide (Gb4) in the presence of cell membrane components such as phosphatidylcholine (PC), cholesterol (Ch) and other neutral glycolipids. In the absence of PC and Ch, holotoxins of Stx2 variants bound to mixtures of Gb3 with other glycolipids but not to Gb3 or Gb4 alone. Binding of all Stx holotoxins significantly increased in the presence of PC and Ch. Previously, Stx2a has been shown to form a less stable B-pentamer compared to Stx1. However, its effect on glycolipid receptor binding is unknown. In this study, we showed that even in the absence of the A-subunit, the B-subunits of both Stx1 and Stx2a were able to bind to the glycolipids and the more stable B-pentamer formed by Stx1 bound better than the less stable pentamer of Stx2a. B-subunit mutant of Stx1 L41Q, which shows similar stability as Stx2a B-subunits, lacked glycolipid binding, suggesting that pentamerization is more critical for binding of Stx1 than Stx2a.

Shiga toxin-producing Escherichia coli in swine: the public health perspective

Shiga toxin-producing Escherichia coli (STEC) strains are food-borne pathogens that are an important public health concern. STEC infection is associated with severe clinical diseases in human beings, including hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS), which can lead to kidney failure and death. Cattle are the most important STEC reservoir. However, a number of STEC outbreaks and HUS cases have been attributed to pork products. In swine, STEC strains are known to be associated with edema disease. Nevertheless, the relationship between STEC of swine origin and human illness has yet to be determined. This review critically summarizes epidemiologic and biological studies of swine STEC. Several epidemiologic studies conducted in multiple regions of the world have demonstrated that domestic swine can carry and shed STEC. Moreover, animal studies have demonstrated that swine are susceptible to STEC O157:H7 infection and can shed the bacterium for 2 months. A limited number of molecular epidemiologic studies, however, have provided conflicting evidence regarding the relationship between swine STEC and human illness. The role that swine play in STEC transmission to people and the contribution to human disease frequency requires further evaluation.

The acyl-homoserine lactone synthase YenI from Yersinia enterocolitica modulates virulence gene expression in enterohemorrhagic Escherichia coli O157:H7

The human pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 colonizes the rectoanal junction (RAJ) in cattle, its natural reservoir. Colonization at the RAJ poses a serious risk for fecal shedding and contamination of the environment. We previously demonstrated that EHEC senses acyl-homoserine lactones (AHLs) produced by the microbiota in the rumen to activate the gad acid resistance genes necessary for survival through the acidic stomachs in cattle and to repress the locus of enterocyte effacement (LEE) genes important for colonization of the RAJ, but unnecessary in the rumen. Devoid of AHLs, the RAJ is the prominent site of colonization of EHEC in cattle. To determine if the presence of AHLs in the RAJ could repress colonization at this site, we engineered EHEC to express the Yersinia enterocolitica AHL synthase gene yenI, which constitutively produces AHLs, to mimic a constant exposure of AHLs in the environment. The yenI(+) EHEC produces oxo-C6-homoserine lactone (oxo-C6-HSL) and had a significant reduction in LEE expression, effector protein secretion, and attaching and effacing (A/E) lesion formation in vitro compared to the wild type (WT). The yenI(+) EHEC also activated expression of the gad genes. To assess whether AHL production, which decreases LEE expression, would decrease RAJ colonization by EHEC, cattle were challenged at the RAJ with WT or yenI(+) EHEC. Although the yenI(+) EHEC colonized the RAJ with efficiency equal to that of the WT, there was a trend for the cattle to shed the WT strain longer than the yenI(+) EHEC.

Enterohemorrhagic E. coli (EHEC) pathogenesis

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 is a human pathogen responsible for outbreaks of bloody diarrhea and hemolytic uremic syndrome (HUS) worldwide. Conventional antimicrobials trigger an SOS response in EHEC that promotes the release of the potent Shiga toxin that is responsible for much of the morbidity and mortality associated with EHEC infection. Cattle are a natural reservoir of EHEC, and approximately 75% of EHEC outbreaks are linked to the consumption of contaminated bovine-derived products. This review will discuss how EHEC causes disease in humans but is asymptomatic in adult ruminants. It will also analyze factors utilized by EHEC as it travels through the bovine gastrointestinal (GI) tract that allow for its survival through the acidic environment of the distal stomachs, and for its ultimate colonization in the recto-anal junction (RAJ). Understanding the factors crucial for EHEC survival and colonization in cattle will aid in the development of alternative strategies to prevent EHEC shedding into the environment and consequent human infection.

Antibody response to Shiga toxins in Argentinean children with enteropathic hemolytic uremic syndrome at acute and long-term follow-up periods

Shiga toxin (Stx)-producing Escherichia coli (STEC) infection is associated with a broad spectrum of clinical manifestations that include diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Systemic Stx toxemia is considered to be central to the genesis of HUS. Distinct methods have been used to evaluate anti-Stx response for immunodiagnostic or epidemiological analysis of HUS cases. The development of enzyme-linked immunosorbent assay (ELISA) and western blot (WB) assay to detect the presence of specific antibodies to Stx has introduced important advantages for serodiagnosis of HUS. However, application of these methods for seroepidemiological studies in Argentina has been limited. The aim of this work was to develop an ELISA to detect antibodies against the B subunit of Stx2, and a WB to evaluate antibodies against both subunits of Stx2 and Stx1, in order to analyze the pertinence and effectiveness of these techniques in the Argentinean population. We studied 72 normal healthy children (NHC) and 105 HUS patients of the urban pediatric population from the surrounding area of Buenos Aires city. Using the WB method we detected 67% of plasma from NHC reactive for Stx2, but only 8% for Stx1. These results are in agreement with the broad circulation of Stx2-expressing STEC in Argentina and the endemic behavior of HUS in this country. Moreover, the simultaneous evaluation by the two methods allowed us to differentiate acute HUS patients from NHC with a great specificity and accuracy, in order to confirm the HUS etiology when pathogenic bacteria were not isolated from stools.

Shiga toxin subtypes display dramatic differences in potency

Purified Shiga toxin (Stx) alone is capable of producing systemic complications, including hemolytic-uremic syndrome (HUS), in animal models of disease. Stx includes two major antigenic forms (Stx1 and Stx2), with minor variants of Stx2 (Stx2a to -h). Stx2a is more potent than Stx1. Epidemiologic studies suggest that Stx2 subtypes also differ in potency, but these differences have not been well documented for purified toxin. The relative potencies of five purified Stx2 subtypes, Stx2a, Stx2b, Stx2c, Stx2d, and activated (elastase-cleaved) Stx2d, were studied in vitro by examining protein synthesis inhibition using Vero monkey kidney cells and inhibition of metabolic activity (reduction of resazurin to fluorescent resorufin) using primary human renal proximal tubule epithelial cells (RPTECs). In both RPTECs and Vero cells, Stx2a, Stx2d, and elastase-cleaved Stx2d were at least 25 times more potent than Stx2b and Stx2c. In vivo potency in mice was also assessed. Stx2b and Stx2c had potencies similar to that of Stx1, while Stx2a, Stx2d, and elastase-cleaved Stx2d were 40 to 400 times more potent than Stx1.

Initial adherence of EPEC, EHEC and VTEC to host cells

Initial adherence to host cells is the first step of the infection of enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic Escherichia coli (EHEC) and verotoxigenic Escherichia coli (VTEC) strains. The importance of this step in the infection resides in the fact that (1) adherence is the first contact between bacteria and intestinal cells without which the other steps cannot occur and (2) adherence is the basis of host specificity for a lot of pathogens. This review describes the initial adhesins of the EPEC, EHEC and VTEC strains. During the last few years, several new adhesins and putative colonisation factors have been described, especially in EHEC strains. Only a few adhesins (BfpA, AF/R1, AF/R2, Ral, F18 adhesins) appear to be host and pathotype specific. The others are found in more than one species and/or pathotype (EPEC, EHEC, VTEC). Initial adherence of EPEC, EHEC and VTEC strains to host cells is probably mediated by multiple mechanisms.

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).

Preventing household transmission of Shiga toxin-producing Escherichia coli O157 infection: promptly separating siblings might be the key

BACKGROUND

Preventing household transmission of Shiga toxin-producing Escherichia coli O157 (STEC O157) infection is important because of the ease of interpersonal transmission and the potential disease severity.

METHODS

We conducted a retrospective cohort study of households associated with an outbreak of STEC O157 infection in South Wales, United Kingdom, in autumn 2005. We investigated whether characteristics of the primary case patient or the household were predictors for secondary household transmission of STEC O157 infection. Furthermore, we estimated the proportion of cases that might be prevented by isolation (e.g., hospitalization) of the primary case patient immediately after the microbiological diagnosis and the number of patients with STEC O157 who would need to be isolated to prevent 1 case of hemolytic uremic syndrome. Based on dates of symptom onset, case patients in households were classified as having primary, coprimary, or secondary infection. Secondary cases were considered to be preventable if the secondary case patient's symptoms started >1 incubation period (4 days) after the date of microbiological diagnosis of the primary case.

RESULTS

Eighty-nine (91%) of 98 eligible households were enrolled. Among 20 households (22%), 25 secondary cases were ascertained. Thirteen secondary cases (56%) occurred in siblings of the primary case patients; hemolytic uremic syndrome developed in 4 of these siblings. Presence of a sibling (risk ratio, 3.8; 95% confidence interval, 0.99-14.6) and young age (<5 years) of the primary case patient (risk ratio, 2.03; 95% confidence interval, 0.99-41.6) were independent predictors for households in which secondary cases occurred. Of the 15 secondary cases for which complete information was available, 7 (46%) might have been prevented. When restricting isolation to primary case patients who were aged <10 years and who had a sibling, we estimated the number of patients who would need to be isolated to prevent 1 case of hemolytic uremic syndrome to be 47 patients (95% confidence interval, 16-78 patients).

CONCLUSIONS

Promptly separating pediatric patients with STEC O157 infection from their young siblings should be considered.

Evaluation of BBL CHROMagar O157 versus sorbitol-MacConkey medium for routine detection of Escherichia coli O157 in a centralized regional clinical microbiology laboratory

The performance of BBL CHROMagar O157 (CHROM) versus that of sorbitol-MacConkey (SMAC) media for detection of Escherichia coli O157 was determined for a 3-month period. Results for 27/3,116 (0.9%) stool cultures were positive. CHROM had a higher sensitivity (96.30%) and negative predictive value (100%) and a better diagnostic efficiency than SMAC. Labor and material costs decreased when CHROM was used.

Shiga toxin-producing Escherichia coli infections associated with hemolytic uremic syndrome, Italy, 1988-2000

The mean annual incidence of hemolytic uremic syndrome in persons </=15 years of age in Italy from 1988 to 2000 was 0.28 per 100,000 population. Laboratory investigations showed that Shiga toxin-producing Escherichia coli (STEC) infection occurred in 73.1% of patients. STEC O157 was the most common serotype, but a considerable number of cases were from infections by non-O157 STEC.

A waterborne outbreak of Escherichia coli O157:H7 infections and hemolytic uremic syndrome: implications for rural water systems

In the summer of 1998, a large outbreak of Escherichia coli O157:H7 infections occurred in Alpine, Wyoming. We identified 157 ill persons; stool from 71 (45%) yielded E. coli O157:H7. In two cohort studies, illness was significantly associated with drinking municipal water (town residents: adjusted odds ratio=10.1, 95% confidence intervals [CI]=1.8-56.4; visitors attending family reunion: relative risk=9.0, 95% CI=1.3-63.3). The unchlorinated water supply had microbiologic evidence of fecal organisms and the potential for chronic contamination with surface water. Among persons exposed to water, the attack rate was significantly lower in town residents than in visitors (23% vs. 50%, p<0.01) and decreased with increasing age. The lower attack rate among exposed residents, especially adults, is consistent with the acquisition of partial immunity following long-term exposure. Serologic data, although limited, may support this finding. Contamination of small, unprotected water systems may be an increasing public health risk.

Sporadic STEC O157 infection: secondary household transmission in Wales

We conducted a study to quantify and characterize household transmission of Shiga toxin (Vero cytotoxin)-producing Escherichia coli O157 (STEC O157) following sporadic infection in Wales. Through total population surveillance, we identified 83 index case-patients and their household contacts. We screened fecal samples submitted from household contacts for STEC O157 and calculated the household transmission rate for sporadic STEC O157 infection to be 4% to 15%. Household contacts in groups at high risk (particularly children under 5 years of age) present a risk of spreading the infection in the wider community.

Haemolytic-uraemic syndrome in the Hunter: public health implications

Three cases of haemolytic-uraemic syndrome in the Hunter area were reported in February 1995. An investigation was initiated to identify any verocytotoxic Escherichia coli in clinical samples that could be associated with the development of the disease. Escherichia coli O6:H- and O2:H7 were isolated from Case 1. No organisms were identified for Case 2, and Case 3 samples yielded Campylobacter jejuni. In addition, efforts were made to trace sources of any such pathogens in food samples or in the environment generally. Shiga-like toxins were found in meat products sampled from butchers' shops patronised by the families of the three cases. However, it was not found possible to match stool samples with samples of food from sources used by the families of the children. Environmental factors seemed likely to have played a significant role in the development of haemolytic-uraemic syndrome in Case 3. It is suggested that the incidence of the disease may be reduced by increasing the frequency of testing of meat products for Shiga-like toxins I and II and through educational and research programs.

The hemolytic uremic syndrome

HUS is the most common cause of acute renal failure in infants and young children and follows a diarrheal prodrome about 90% of the time. Persuasive evidence shows that virtually all of postdiarrheal cases are caused by EHEC infections, and that the great majority of cases in the United States are caused by the EHEC serotype O157:H7. Mortality is approximately 5%, and approximately 10% of survivors are left with severe sequelae. A much larger number (30%-50%) experience mild chronic renal damage. Public health strategies, including zero tolerance for fecal contamination in slaughter houses and additional public education on proper food handling and cooking, does much to decrease the prevalence of the syndrome. Efforts to further dissect the postdiarrheal pathogenic cascade should continue, and an animal model needs to be developed. Only then will researchers be positioned to develop effective intervention strategies. Preventing life-threatening extrarenal complications, especially of the CNS, is a major challenge. Idiopathic nondiarrheal HUS accounts for approximately 10% of cases and comprises a poorly understood composite of HUS subsets. Research directed toward a better understanding of these mysterious variants also is a priority for the years ahead.

Characterization of verocytotoxin-producing Escherichia coli O157 isolates from patients with haemolytic uraemic syndrome in Western Europe

Fifty verocytotoxin (VT)-producing Escherichia coli (VTEC) strains of serogroup O157 were characterized by phage typing, polymerase chain reaction (PCR) for VT genes and the E. coli attaching and effacing (eae) gene, and random amplified polymorphic DNA-PCR (RAPD-PCR) fingerprinting. The collection represented isolates obtained from patients with diarrhoea-associated haemolytic-uraemic syndrome (D+ HUS) and their family contacts, isolated in the Netherlands, Belgium and Germany between 1989 and 1993. Based on isolates from separate families (n = 27) seven different phage types were identified, types 2 (44%) and 4 (33%) were predominant. Eighty-five percent of the strains contained only VT2 gene sequences and 15% both VT1 and VT2. All strains of the dominant phage types 2 and 4 carried the VT2 gene. Strains that belonged to the minor phage types 8, 14, 32 carried both VT1 and VT2 genes, with the exception of two isolates identified as phage types 49 and 54 which contained only VT2 genes. All O157 VTEC strains possessed the chromosomally-located eae gene, which indicates its usefulness as virulence marker. RAPD-PCR fingerprinting identified four distinct banding patterns, with one profile found among 79% of the strains. Based on the combined results of all typing methods used in this study, the collection of 50 O157 VTEC strains could be divided into nine distinct groups. Strains isolated from different persons within one family could not be distinguished by any of these methods. The data suggest that O157 VTEC strains are members of one clone that has become widely distributed.

Haemolytic-uraemic syndrome in childhood: surveillance and case-control studies in Italy. Italian HUS Study Group

Seventy-six cases of haemolytic-uraemic syndrome (HUS) were collected over a 4-year period during a surveillance and case-control study. The annual incidence of 0.2 per 100,000 children aged 0-14 years is lower than in other countries; 34% had no prodromal diarrhoea. Evidence for verocytotoxin-producing Escherichia coli (VTEC) infection was found in 72% of patients and 3% of controls; 88% of patients with bloody diarrhoea, 67% with non-bloody diarrhoea and 55% without diarrhoea were VTEC positive. Seventy-three percent of patients had creatinine clearance > or = 80 ml/min per 1.73 m2, normal blood pressure, no proteinuria and haematuria < 2+ after 1 year of follow-up. One patient died and none had non-renal sequelae. VTEC positivity was significantly correlated with a good outcome, while the absence of diarrhoea and a high total white blood cell count at onset were not predictors of a bad outcome. Household contacts of HUS patients had diarrhoea more frequently than those of the control group, supporting the hypothesis of person-to-person transmission of VTEC infection.

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.

Epidemic Escherichia coli O157:H7 gastroenteritis and hemolytic-uremic syndrome in a Canadian inuit community: intestinal illness in family members as a risk factor

OBJECTIVE

To evaluate risk factors for childhood hemolytic-uremic syndrome (HUS) and gastroenteritis during an epidemic of Escherichia coli O157:H7 infection.

DESIGN

Case-control study.

SETTING

Remote Inuit community of Arviat in northern Canada.

PARTICIPANTS

Of the 565 Arviat residents less than 15 years of age, 19 had HUS and 65 more had E. coli O157:H7 gastroenteritis. The 19 children with HUS were compared with 19 age- and gender-matched children with uncomplicated E. coli O157:H7 gastroenteritis, and both HUS and gastroenteritis patients were compared with 19 healthy control subjects.

INTERVENTIONS

Questionnaire administered face-to-face to parents of participants in the home.

MAIN OUTCOME MEASURES

Rates of exposure to foods, travel, sources of water, and gastrointestinal illness in family members.

RESULTS

Patients with HUS and those with uncomplicated E. coli O157:H7 gastroenteritis differed only on measures of clinical severity. In the 7 days before the onset of gastrointestinal symptoms, children with HUS and those with uncomplicated gastroenteritis were more likely to have been exposed to a family member with diarrhea than were the healthy control subjects (odds ratio = 9 for HUS vs healthy control subjects; 95% confidence interval 2 to 43; p < 0.01). Undercooked ground meat and foods traditionally consumed by the Inuit were not implicated as risk factors in E. coli O157:H7 infection.

CONCLUSIONS

These findings emphasize the potential for extensive intrafamilial transmission of verotoxin-producing E. coli once infection is introduced into certain communities.