Primary and secondary cases in Escherichia coli O157 outbreaks: a statistical analysis

Shedding and exclusion from childcare in children with Shiga toxin-producing Escherichia coli, 2018-2022

Excluding children with Shiga toxin-producing Escherichia coli (STEC) from childcare until microbiologically clear of the pathogen, disrupts families, education, and earnings. Since PCR introduction, non-O157 STEC serotype detections in England have increased. We examined shedding duration by serotype and transmission risk, to guide exclusion advice. We investigated STEC cases aged <6 years, residing in England and attending childcare, with diarrhoea onset or sample date from 31 March 2018 to 30 March 2022. Duration of shedding was the interval between date of onset or date first positive specimen and earliest available negative specimen date. Transmission risk was estimated from proportions with secondary cases in settings attended by infectious cases. There were 367 cases (STEC O157 n = 243, 66.2%; STEC non-O157 n = 124, 33.8%). Median shedding duration was 32 days (IQR 20-44) with no significant difference between O157 and non-O157; 2% (n = 6) of cases shed for ≥100 days. Duration of shedding was reduced by 17% (95% CI 4-29) among cases reporting bloody diarrhoea. Sixteen settings underwent screening; four had secondary cases (close contacts' secondary transmission rate = 13%). Shedding duration estimates were consistent with previous studies (median 31 days, IQR 17-41). Findings do not warrant guidance changes regarding exclusion and supervised return of prolonged shedders, despite serotype changes.

Etiological diagnosis of post-diarrheal hemolytic uremic syndrome (HUS): humoral response contribution

BACKGROUND

Hemolytic uremic syndrome (HUS) is characterized by microangiopathic hemolysis, thrombocytopenia, and thrombus formation leading to tissue injury. HUS is classified according to its etiology as post-diarrheal or atypical HUS. Differential diagnosis of both entities continues to be a challenge for pediatric physicians.

METHODS

The aim was to improve the rapid etiological diagnosis of post-diarrheal HUS cases based on the detection of Shiga toxin (Stx)-producing Escherichia coli (STEC) infection by screening of stx_1/stx₂ and rfb_O157 in cultured stools by multiplex PCR, and the additional detection of anti-lipopolysaccharide (anti-LPS) O157, O145, and O121 antibodies by Glyco-iELISA test. In addition, we studied patients' relatives to detect circulating pathogenic strains that could contribute to HUS diagnosis and/or lead to the implementation of measures to prevent dissemination of familial outbreaks. This study describes the diagnosis of 31 HUS patients admitted to Hospital Municipal de Niños Prof Dr Ramón Exeni during the 2017-2020 period.

RESULTS

Stool PCR confirmed the diagnosis of STEC associated with HUS in 38.7% of patients (12/31), while anti-LPS serology did in 88.9% (24/27). In those patients in which both methods were carried out (n = 27), a strong association between the results obtained was found. We found that 30.4% of HUS patients had at least one relative positive for STEC.

CONCLUSIONS

We could identify 96.3% (26/27) of HUS cases as secondary to STEC infections when both methods (genotyping and serology) were used. The results demonstrated a high circulation of STEC in HUS families and the prevalence of the STEC O157 serotype (83%) in our pediatric cohort. A higher-resolution version of the Graphical abstract is available as Supplementary information.

Three Novel Antisense Overlapping Genes in E. coli O157:H7 EDL933

The abundance of long overlapping genes in prokaryotic genomes is likely to be significantly underestimated. To date, only a few examples of such genes are fully established. Using RNA sequencing and ribosome profiling, we found expression of novel overlapping open reading frames in Escherichia coli O157:H7 EDL933 (EHEC). Indeed, the overlapping candidate genes are equipped with typical structural elements required for transcription and translation, i.e., promoters, transcription start sites, as well as terminators, all of which were experimentally verified. Translationally arrested mutants, unable to produce the overlapping encoded protein, were found to have a growth disadvantage when grown competitively against the wild type. Thus, the phenotypes found imply biological functionality of the genes at the level of proteins produced. The addition of 3 more examples of prokaryotic overlapping genes to the currently limited, yet constantly growing pool of such genes emphasizes the underestimated coding capacity of bacterial genomes. IMPORTANCE The abundance of long overlapping genes in prokaryotic genomes is likely to be significantly underestimated, since such genes are not allowed in genome annotations. However, ribosome profiling catches mRNA in the moment of being template for protein production. Using this technique and subsequent experiments, we verified 3 novel overlapping genes encoded in antisense of known genes. This adds more examples of prokaryotic overlapping genes to the currently limited, yet constantly growing pool of such genes.

First molecular characterization of Escherichia coli O157:H7 isolates from clinical samples in Paraguay using whole-genome sequencing

Escherichia coli O157:H7 is a foodborne pathogen implicated in numerous outbreaks worldwide that has the ability to cause extra-intestinal complications in humans. The Enteropathogens Division of the Central Public Health Laboratory (CPHL) in Paraguay is working to improve the genomic characterization of Shiga toxin-producing E. coli (STEC) to enhance laboratory-based surveillance and investigation of foodborne disease outbreaks. Whole genome sequencing (WGS) is proposed worldwide to be used in the routine laboratory as a high-resolution tool that allows to have all the results in a single workflow. This study aimed to carry out for the first time, the genomic characterization by WGS of nine STEC O157:H7 strains isolated from human samples in Paraguay. We were able to identify virulence and resistance mechanisms, MLST subtype, and even establish the phylogenetic relationships between isolates. Furthermore, we detected the presence of strains belonging to hypervirulent clade 8 in most of the isolates studied.

Genomic Analysis of Shiga Toxin-Producing E. coli O157 Cattle and Clinical Isolates from Alberta, Canada

Shiga toxin (stx) is the principal virulence factor of the foodborne pathogen, Shiga toxin-producing Escherichia coli (STEC) O157:H7 and is associated with various lambdoid bacterio (phages). A comparative genomic analysis was performed on STEC O157 isolates from cattle (n = 125) and clinical (n = 127) samples to characterize virulence genes, stx-phage insertion sites and antimicrobial resistance genes that may segregate strains circulating in the same geographic region. In silico analyses revealed that O157 isolates harboured the toxin subtypes stx1a and stx2a. Most cattle (76.0%) and clinical (76.4%) isolates carried the virulence gene combination of stx1, stx2, eae and hlyA. Characterization of stx1 and stx2-carrying phages in assembled contigs revealed that they were associated with mlrA and wrbA insertion sites, respectively. In cattle isolates, mlrA and wrbA insertion sites were occupied more often (77% and 79% isolates respectively) than in clinical isolates (38% and 1.6% isolates, respectively). Profiling of antimicrobial resistance genes (ARGs) in the assembled contigs revealed that 8.8% of cattle (11/125) and 8.7% of clinical (11/127) isolates harboured ARGs. Eight antimicrobial resistance genes cassettes (ARCs) were identified in 14 isolates (cattle, n = 8 and clinical, n = 6) with streptomycin (aadA1, aadA2, ant(3’’)-Ia and aph(3’’)-Ib) being the most prevalent gene in ARCs. The profound disparity between the cattle and clinical strains in occupancy of the wrbA locus suggests that this trait may serve to differentiate cattle from human clinical STEC O157:H7. These findings are important for stx screening and stx-phage insertion site genotyping as well as monitoring ARGs in isolates from cattle and clinical samples.

Examining the role of person-to-person transmission during a verocytotoxigenic Escherichia coli outbreak in Ontario, Canada

OBJECTIVE

Person-to-person transmission can occur during outbreaks of verotoxigenic Escherichia coli (VTEC), however the impact of this transmission route is not well understood. This study aimed to examine the role of person-to-person transmission during a VTEC outbreak, and how targeting this route may reduce outbreak size. A deterministic compartmental model describing a VTEC outbreak was constructed and fit to data from a 2008 outbreak in Ontario, Canada. Using the best-fit model, simulations were run to calculate the: reduction in transmission rate after implementing interventions, proportion of cases infected through both transmission routes, and number of cases prevented by interventions. Latin hypercube sensitivity analysis was conducted to examine the sensitivity of the outbreak size to the model parameters.

RESULTS

Based on the best-fit model, ~ 14.25% of the cases likely arose due to person-to-person transmission. Interventions reduced this transmission rate by ~ 73%, causing a reduction in outbreak size of ~ 17% (47 cases). Sensitivity analysis showed that the model was highly sensitive to changes in all parameters of the model. The model demonstrates that person-to-person could be an important transmission route during VTEC outbreaks. Targeting this route of transmission through hand hygiene and work exclusions could reduce the final outbreak size.

Family Clusters of Shiga Toxin-producing Escherichia coli Infection: An Overlooked Source of Transmission. Data From the ItalKid-Hus Network

BACKGROUND

The aim of the present work was to investigate family clusters of Shiga toxin-producing Escherichia coli (STEC) infection among the household members of STEC positive patients, identified within a screening program of bloody diarrhea (BD) for STEC in Northern Italy.

METHODS

Stool samples from patients with BD or BD-associated-hemolytic uremic syndrome (HUS) and related households were investigated by molecular and bacteriologic methods to detect and characterize the virulence profile of STEC and Pulsed Field Gel Electrophoresis analysis were done on isolates.

RESULTS

Thirty-nine cases of STEC infection (isolated BD in 16, BD-associated-HUS in 23) were considered, and a total of 130 stool samples from 1 to 8 households of the index patient were analyzed. The prevalence of positivity was higher in siblings (34.8%, 8/23) than in mothers (20%, 7/35), grandparents (9.5%, 2/21), fathers (8.8%, 3/34) or other households. In 14 clusters (36%), one or more household shared a STEC with the same virulence profile (stx, eae, serogroup) as the index case. In 7 clusters, STEC strains isolated from at least 2 subjects also shared identical Pulsed Field Gel Electrophoresis profile. The frequency of household infection does not appear to be associated to the index case's illness (HUS or BD), nor with the serotype or with the virulence profile of the involved STEC (stx2 or stx1-stx2).

CONCLUSIONS

Our study shows that STEC infections, most likely related to human-to-human transmission, are common among households of patients with STEC BD or HUS and underlines the importance of extending the epidemiologic investigations to all family members, as the index case may not always be the primary infection in the family.

Background prevalence of subclinical Shiga toxin-producing Escherichia coli in children attending childcare facilities in the Irish Midlands

BACKGROUND

Exclusion of asymptomatic shedders of Shiga toxin-producing Escherichia coli (STEC) from childcare facilities (CCFs) is a recognized measure to minimize risk of secondary transmission. This is predicated on factors including an assumption of low background prevalence of STEC amongst CCF attendees. There is a paucity of scientific evidence regarding the true prevalence of STEC in paediatric populations. The study aimed to develop and test a methodology to estimate background prevalence of STEC amongst CCF attendees at regional level in Ireland.

METHODS

Computerized Infectious Disease Reporting data were used to compile a list of outbreaks of STEC occurring in CCFs in the Irish Midlands since the introduction of polymerase chain reaction (PCR)-based testing. Laboratory data were used to determine background prevalence of STEC in screened children in each outbreak individually and across all outbreaks.

RESULTS

A pooled summary prevalence estimate of 2.9% (95% confidence interval 1.4-5.5%) was determined for the entire screened cohort across all outbreaks. Sensitivity analysis supported the validity of the estimate.

CONCLUSIONS

The relatively high prevalence estimate of 2.9% suggests that a public health risk assessment approach to return of prolonged asymptomatic shedders to the CCF may be appropriate in peak STEC season in the Midlands.

Phylogeographic Analysis Reveals Multiple International transmission Events Have Driven the Global Emergence of Escherichia coli O157:H7

BACKGROUND

Shiga toxin-producing Escherchia coli (STEC) O157:H7 is a zoonotic pathogen that causes numerous food and waterborne disease outbreaks. It is globally distributed, but its origin and the temporal sequence of its geographical spread are unknown.

METHODS

We analyzed whole-genome sequencing data of 757 isolates from 4 continents, and performed a pan-genome analysis to identify the core genome and, from this, extracted single-nucleotide polymorphisms. A timed phylogeographic analysis was performed on a subset of the isolates to investigate its worldwide spread.

RESULTS

The common ancestor of this set of isolates occurred around 1890 (1845-1925) and originated from the Netherlands. Phylogeographic analysis identified 34 major transmission events. The earliest were predominantly intercontinental, moving from Europe to Australia around 1937 (1909-1958), to the United States in 1941 (1921-1962), to Canada in 1960 (1943-1979), and from Australia to New Zealand in 1966 (1943-1982). This pre-dates the first reported human case of E. coli O157:H7, which was in 1975 from the United States.

CONCLUSIONS

Inter- and intra-continental transmission events have resulted in the current international distribution of E. coli O157:H7, and it is likely that these events were facilitated by animal movements (eg, Holstein Friesian cattle). These findings will inform policy on action that is crucial to reduce the further spread of E. coli O157:H7 and other (emerging) STEC strains globally.

Quantitative Microbial Risk Assessment and Infectious Disease Transmission Modeling of Waterborne Enteric Pathogens

PURPOSE OF REVIEW

Waterborne enteric pathogens remain a global health threat. Increasingly, quantitative microbial risk assessment (QMRA) and infectious disease transmission modeling (IDTM) are used to assess waterborne pathogen risks and evaluate mitigation. These modeling efforts, however, have largely been conducted independently for different purposes and in different settings. In this review, we examine the settings where each modeling strategy is employed.

RECENT FINDINGS

QMRA research has focused on food contamination and recreational water in high-income countries (HICs) and drinking water and wastewater in low- and middle-income countries (LMICs). IDTM research has focused on large outbreaks (predominately LMICs) and vaccine-preventable diseases (LMICs and HICs). Human ecology determines the niches that pathogens exploit, leading researchers to focus on different risk assessment research strategies in different settings. To enhance risk modeling, QMRA and IDTM approaches should be integrated to include dynamics of pathogens in the environment and pathogen transmission through populations.

The novel EHEC gene asa overlaps the TEGT transporter gene in antisense and is regulated by NaCl and growth phase

Only a few overlapping gene pairs are known in the best-analyzed bacterial model organism Escherichia coli. Automatic annotation programs usually annotate only one out of six reading frames at a locus, allowing only small overlaps between protein-coding sequences. However, both RNAseq and RIBOseq show signals corresponding to non-trivially overlapping reading frames in antisense to annotated genes, which may constitute protein-coding genes. The transcription and translation of the novel 264 nt gene asa, which overlaps in antisense to a putative TEGT (Testis-Enhanced Gene Transfer) transporter gene is detected in pathogenic E. coli, but not in two apathogenic E. coli strains. The gene in E. coli O157:H7 (EHEC) was further analyzed. An overexpression phenotype was identified in two stress conditions, i.e. excess in salt or arginine. For this, EHEC overexpressing asa was grown competitively against EHEC with a translationally arrested asa mutant gene. RT-qPCR revealed conditional expression dependent on growth phase, sodium chloride, and arginine. Two potential promoters were computationally identified and experimentally verified by reporter gene expression and determination of the transcription start site. The protein Asa was verified by Western blot. Close homologues of asa have not been found in protein databases, but bioinformatic analyses showed that it may be membrane associated, having a largely disordered structure.

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.

An outbreak of Escherichia coli O157:H7 infections following a dairy education school field trip in Washington state, 2015

On 27 April 2015, Washington health authorities identified Escherichia coli O157:H7 infections associated with dairy education school field trips held in a barn 20-24 April. Investigation objectives were to determine the magnitude of the outbreak, identify the source of infection, prevent secondary illness transmission and develop recommendations to prevent future outbreaks. Case-finding, hypothesis generating interviews, environmental site visits and a case-control study were conducted. Parents and children were interviewed regarding event activities. Odds ratios (OR) and 95% confidence intervals (CI) were computed. Environmental testing was conducted in the barn; isolates were compared to patient isolates using pulsed-field gel electrophoresis (PFGE). Sixty people were ill, 11 (18%) were hospitalised and six (10%) developed haemolytic uremic syndrome. Ill people ranged in age from <1 year to 47 years (median: 7), and 20 (33%) were female. Twenty-seven case-patients and 88 controls were enrolled in the case-control study. Among first-grade students, handwashing (i.e. soap and water, or hand sanitiser) before lunch was protective (adjusted OR 0.13; 95% CI 0.02-0.88, P = 0.04). Barn samples yielded E. coli O157:H7 with PFGE patterns indistinguishable from patient isolates. This investigation provided epidemiological, laboratory and environmental evidence for a large outbreak of E. coli O157:H7 infections from exposure to a contaminated barn. The investigation highlights the often overlooked risk of infection through exposure to animal environments as well as the importance of handwashing for disease prevention. Increased education and encouragement of infection prevention measures, such as handwashing, can prevent illness.

Current Interventions for Controlling Pathogenic Escherichia coli

This review examined scientific reports and articles published from 2007 to 2016 regarding the major environmental sources of pathogenic Escherichia coli and the routes by which they enter the human gastrointestinal tract. The literature describes novel techniques used to combat pathogenic E. coli transmitted to humans from livestock and agricultural products, food-contact surfaces in processing environments, and food products themselves. Although prevention before contamination is always the best "intervention," many studies aim to identify novel chemical, physical, and biological techniques that inactivate or eliminate pathogenic E. coli cells from breeding livestock, growing crops, and manufactured food products. Such intervention strategies target each stage of the food chain from the perspective of "Farm to Table food safety" and aim to manage major reservoirs of pathogenic E. coli throughout the entire process. Issues related to, and recent trends in, food production must address not only the safety of the food itself but also the safety of those who consume it. Thus, research aims to discover new "natural" antimicrobial agents and to develop "multiple hurdle technology" or other novel technologies that preserve food quality. In addition, this review examines the practical application of recent technologies from the perspective of product quality and safety. It provides comprehensive insight into intervention measures used to ensure food safety, specifically those aimed at pathogenic E. coli.

Competition during enrichment of pathogenicEscherichia colimay result in culture bias

Deadly outbreaks and illnesses due to Shiga toxin-producing Escherichia coli (STEC) occur worldwide; however, the cultivation methods required for adequate monitoring and traceback investigations are inefficient at best. Detection of STEC relies heavily on enrichment; yet no standard media or protocols exist. Furthermore, whether enrichment may bias detection of multiple STEC serogroups from complex samples is unknown. Thus, 14 STEC strains of serogroups O157 and the top six non-O157s (O26, O45, O103, O111, O121, and O145) were enriched in pairs for 6–78 h in broth and evaluated by quantitative polymerase chain reaction (qPCR). Here we show that a conventional 6-h enrichment protocol did not result in intra-species culture bias for the isolates tested. However, subsequent enrichments often produced biased cultures, with differences in the qPCR gene copy number ≥2 log10apparent in 12%, 38%, and 52% of competitions after 30, 54, and 78 h of consecutive enrichments, respectively. Some strains were able to prevail and (or) out-compete the opponent strain in 100% of competitions. Our results suggest that culture bias should be considered and (or) evaluated further due to the potential implications during routine pathogen screening and outbreak investigations.

Prevention of secondary household transmission during Shiga toxin-producing Escherichia coli outbreaks

Prevention of secondary household transmission of Shiga toxin-producing Escherichia coli (STEC) is important in outbreak settings. We examined factors contributing to secondary household transmission during STEC outbreaks in daycare centres in Japan. Suspected STEC outbreaks in daycare centres were identified by the National Epidemiological Surveillance of Infectious Diseases. Questionnaires were sent to local health centres that responded to outbreaks. Secondary household transmission rates were calculated, and factors affecting secondary household transmission rate were analysed by multilevel analysis. The secondary household transmission rates in 16 outbreaks ranged from 0% to 34·4% (median 4·4%). The highest rate (23·0%) was observed in siblings aged 6-9 years, and the infection rate was significantly higher for mothers than for fathers and grandparents (P < 0·05). Using multilevel analysis, the following variables were selected in the best model: information provided face-to-face (vs. letter or telephone) to families of children in daycare centres (at initial response), STEC type and lag time (days) between onset and providing information. Early response and hygiene education by visiting local health centre staff may be effective measures to prevent secondary household transmission in STEC outbreaks. Hygiene education should be emphasized for children aged 6-9 years, as well as for younger children.

Faecal carriage of extended-spectrum β-lactamase-producing Enterobacteriaceae and Shiga toxin-producing Escherichia coli in asymptomatic nursery children in Lower Saxony (Germany), 2014

Children may be at higher risk for carriage of antimicrobial-resistant bacteria because of higher usage of antimicrobials. They also have higher rates of Shiga toxin-producing Escherichia coli (STEC) infections than other population groups. Some infections, particularly in children, are asymptomatic, but still lead to the excretion of large numbers of bacteria and viruses that may cause clinical disease in other individuals. That is one reason why, in Lower Saxony as in other German federal states - asymptomatic carriers of STEC are excluded from nurseries and schools until three consecutive stool samples test negative in order to prevent secondary cases. The prevalence of children who are asymptomatic STEC carriers is unknown. But if it is high, this measure would have substantial socioeconomic effects on families. Infections with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are an increasing problem for public health, especially for hospitals. However, there are no reliable estimates of the prevalence of asymptomatic ESBL-E carriers in Lower Saxony, as there is no mandatory requirement to report these carriers. In order to discuss the exclusion policies for children attending nurseries and ascertain a baseline of ESBL-E carriers, we conducted a cross-sectional study. The aim was to determine the prevalence of ESBL-E and STEC and identify risk factors for carriage in nursery children without diarrhoea (asymptomatic) aged 0-6 years in four selected districts in Northern Germany. During April-September 2014, we collected stool specimens with the support of voluntarily participating nurseries. We tested for STEC by PCR and for ESBL-E on chromogenic agar. Questionnaires answered by parents contained data on eating and drinking habits, outdoor activities, prior antibiotic treatment and animal contact for each participating child. We compared the epidemiological characteristics of ESBL-E carriers vs. non-carriers by using univariable analysis (P value, odds ratio and 95% confidence interval). We could not perform a statistical analysis for STEC carriers due to the low numbers of positive STEC specimens. Of 224 asymptomatic nursery children, we found a prevalence of 2·3% for ESBL-E carriage and 0·5% for STEC carriage. Asymptomatic ESBL-E carriers were more likely to have consumed raw milk, have had contact with pet rodents, or to have taken antibiotics during the preceding 6 months. We also found a high proportion of raw milk consumption (11%). We suggest that the low STEC prevalence in asymptomatic children supports the current practice of excluding STEC carriers from nurseries. The association between ESBL-E carriage and raw milk consumption and contact with pet rodents needs further investigation.

Changing Diagnostic Methods and Increased Detection of Verotoxigenic Escherichia coli, Ireland

The recent paradigm shift in infectious disease diagnosis from culture-based to molecular-based approaches is exemplified in the findings of a national study assessing the detection of verotoxigenic Escherichia coli infections in Ireland. The methodologic changes have been accompanied by a dramatic increase in detections of non-O157 verotoxigenic E. coli serotypes.

Comparison of the incidence of pathogenic and antibiotic-resistant Escherichia coli strains in adult cattle and veal calf slaughterhouse effluents highlighted different risks for public health

The goal of this study was to investigate the involvement of bovine slaughterhouse effluents and biosolids in the risk of environmental dissemination of pathogenic and antibiotic-resistant Escherichia coli. Several samples were collected from one adult cattle and one veal calf slaughterhouse wastewater treatment plant (WWTP). The treatment process had no impact on the percentage of Shiga toxin-producing E. coli (STEC) and on the percentage of atypical enteropathogenic E. coli (aEPEC). A STEC O157:H7 was isolated from the thickened sludge of the adult cattle slaughterhouse. As thickened sludge is intended to be spread on agricultural lands, the detection of this pathogenic strain is a public health issue. The percentage of antibiotic-resistant E. coli was 5.0% and 87.5% in wastewater from the adult cattle and the veal calf slaughterhouse, respectively. These percentages were not significantly different after treatment. Integron-bearing E. coli isolates were only detected in the veal calf slaughterhouse WWTP with percentages above 50.0% for all sampling points whatever the step of the treatment process. Taken together, these findings highlighted the fact that different public health risks might be associated with adult cattle or veal calf slaughterhouses regarding the dissemination of pathogenic and antibiotic-resistant E. coli isolates into the environment.

Enterohemorrhagic Escherichia coli outbreaks related to childcare facilities in Japan, 2010-2013

Background

Enterohemorrhagic Escherichia coli (EHEC) is an important cause of gastroenteritis in Japan. Although non-O157 EHEC infections have been increasingly reported worldwide, their impact on children has not been well described.

Methods

We collected national surveillance data of EHEC infections reported between 2010 and 2013 in Japan and characterized outbreaks that occurred in childcare facilities. Per Japanese outbreak investigation protocol, faecal samples from contacts of EHEC cases were collected regardless of symptomatic status. Cases and outbreaks were described by demographics, dates of diagnosis and onset, clinical manifestations, laboratory data, and relation to specific outbreaks in childcare facilities.

Results

During 2010–2013, a total of 68 EHEC outbreaks comprised of 1035 cases were related to childcare facilities. Among the 66 outbreaks caused by a single serogroup, 29 were serogroup O26 and 22 were O157; 35 outbreaks were caused by stx1-producing strains. Since 2010, the number of reported outbreaks steadily increased, with a rise in cases and outbreaks caused by stx1-producing O26. Of 7069 EHEC cases reported nationally in 2010–2011, the majority were caused by O157 (n = 4938), relative to O26 (n = 1353) and O111 (n = 195). However, relative to 69 cases of O157 (2 %) associated with childcare facility EHEC outbreaks, there were 131 (10 %) such cases of O26, and this trend intensified in 2012–2013 (O157, 3 %; O26, 24 %; O111, 48 %). Among family members of childcare facility cases, the proportion of cases that were symptomatic declined with age; 10/16 cases (63 %) aged 6 years or younger, 16/53 cases (30 %) 6–19 years old, 23/120 cases (19 %) 20–49 years old and 2/28 cases (7 %) 50 years or older were symptomatic. Thirty one of the 68 outbreaks (46 %) were classified as foodborne-related.

Conclusions

Childcare facility EHEC outbreaks due to non-O157 serogroups, particularly O26 and O111, increased during 2010–2013. These facilities should pay extra attention to health conditions in children. As older family members of childcare facility cases appear to be less symptomatic, they should be vigilant about hand-washing to prevent further transmission.

Whole Genome Sequencing demonstrates that Geographic Variation of Escherichia coli O157 Genotypes Dominates Host Association

Genetic variation in an infectious disease pathogen can be driven by ecological niche dissimilarities arising from different host species and different geographical locations. Whole genome sequencing was used to compare E. coli O157 isolates from host reservoirs (cattle and sheep) from Scotland and to compare genetic variation of isolates (human, animal, environmental/food) obtained from Scotland, New Zealand, Netherlands, Canada and the USA. Nei’s genetic distance calculated from core genome single nucleotide polymorphisms (SNPs) demonstrated that the animal isolates were from the same population. Investigation of the Shiga toxin bacteriophage and their insertion sites (SBI typing) revealed that cattle and sheep isolates had statistically indistinguishable rarefaction profiles, diversity and genotypes. In contrast, isolates from different countries exhibited significant differences in Nei’s genetic distance and SBI typing. Hence, after successful international transmission, which has occurred on multiple occasions, local genetic variation occurs, resulting in a global patchwork of continental and trans-continental phylogeographic clades. These findings are important for three reasons: first, understanding transmission and evolution of infectious diseases associated with multiple host reservoirs and multi-geographic locations; second, highlighting the relevance of the sheep reservoir when considering farm based interventions; and third, improving our understanding of why human disease incidence varies across the world.

School outbreak of Escherichia coli O157 with high levels of transmission, Staffordshire, England, February 2012

BACKGROUND

Verocytotoxin-producing Escherichia coli (VTEC) are bacteria that cause infectious gastroenteritis and in certain settings can cause widespread infection due to secondary transmission. We describe the findings of an investigation of a school-based outbreak of VTEC in Staffordshire, England.

METHODS

Outbreak investigation at a school in February 2012 after two children were diagnosed with VTEC infection. Cases were defined as pupils and staff (or their household contacts) with gastrointestinal symptoms or asymptomatic screened persons, with laboratory confirmed VTEC O157 infection (phage type 32, verocytotoxin 2) occurring on or after 1 February 2012. Microbiological tests of food and faecal samples plus screening of asymptomatic contacts were undertaken. Epidemiological and clinical data were descriptively analysed.

RESULTS

Thirty-eight cases were detected. Nineteen were asymptomatic and identified via screening of 191 pupils. Infection was introduced into the school from an earlier household cluster, followed by extensive person-to-person transmission within the nursery/infant group with limited spread to the wider school population.

CONCLUSIONS

Control measures included several interventions, in particular, universal screening of pupils and staff. Screening during school outbreaks is not underpinned by guidance but proved to be a key control measure. Screening of asymptomatic contacts should be considered in similar outbreaks.

A large Great Britain-wide outbreak of STEC O157 phage type 8 linked to handling of raw leeks and potatoes

Between December 2010 and July 2011, 252 cases of STEC O157 PT8 stx1 + 2 infection were reported in England, Scotland and Wales. This was the largest outbreak of STEC reported in England and the second largest in the UK to date. Eighty cases were hospitalized, with two cases of haemolytic uraemic syndrome and one death reported. Routine investigative data were used to generate a hypothesis but the subsequent case-control study was inconclusive. A second, more detailed, hypothesis generation exercise identified consumption or handling of vegetables as a potential mode of transmission. A second case-control study demonstrated that cases were more likely than controls to live in households whose members handled or prepared leeks bought unwrapped [odds ratio (OR) 40, 95% confidence interval (CI) 2·08-769·4], and potatoes bought in sacks (OR 13·13, 95% CI 1·19-145·3). This appears to be the first outbreak of STEC O157 infection linked to the handling of leeks.

Implications of screening and childcare exclusion policies for children with Shiga-toxin producing Escherichia coli infections: lessons learned from an outbreak in a daycare centre, Norway, 2012

Background

In Norway, it is recommended that children with Shiga-Toxin producing Escherichia coli (STEC) infections are excluded from daycare centers until up to five consecutive negative stool cultures are obtained. Children with gastrointestinal illness of unknown etiology are asked to remain home for 48 hours after symptoms subside. On 16 October 2012, two cases of STEC infection were reported from a daycare center, where other children were also symptomatic. Local health authorities temporarily closed the daycare center and all children and staff were screened for pathogenic E. coli. We present the results of the outbreak investigation in order to discuss the implications of screening and the exclusion policies for children attending daycare in Norway.

Methods

Stool specimens for all children (n = 91) and employees at the daycare center (n = 40) were tested for pathogenic E. coli. Information on demographics, symptoms and potential exposures was collected from parents through trawling interviews and a web-based questionnaire. Cases were monitored to determine the duration of shedding and the resulting exclusion period from daycare.

Results

We identified five children with stx1- and eae-positive STEC O103:H2 infections, and one staff member and one child with STEC O91:H- infections. Three additional children who tested positive for stx1 and eae genes were considered probable STEC cases. Three cases were asymptomatic. Median length of time of exclusion from daycare for STEC cases was 53 days (range 9 days – 108 days). Survey responses for 75 children revealed mild gastrointestinal symptoms among both children with STEC infections and children with negative microbiological results. There was no evidence of common exposures; person-to-person transmission was likely.

Conclusions

The results of screening indicate that E. coli infections can spread in daycare centres, reflected in the proportion of children with STEC and EPEC infections. While screening can identify asymptomatic cases, the implications should be carefully considered as it can produce unanticipated results and have significant socioeconomic consequences. Daycare exclusion policies should be reviewed to address the management of prolonged asymptomatic shedders.

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Person-to-person transmission of norovirus resulting in an outbreak of acute gastroenteritis at a summer camp

BACKGROUND

A significant proportion of norovirus (NV) gastroenteritis outbreaks described in the Spanish literature have been because of contaminated food or water.

AIM

This study describes an outbreak of acute gastroenteritis because of NV in which there was person-to-person transmission.

MATERIALS AND METHODS

A retrospective cohort study was carried out; we established the case definition for primary and secondary cases. An epidemiological survey was designed, including possible food exposures, and clinical and laboratory data. Water and stool samples were taken from affected individuals and food handlers. The presence of NV was detected using a reverse transcription-PCR assay. We analyzed the risk of gastroenteritis using relative risk and its 95% confidence interval as the measure of association, and estimated the basic reproductive number (R0).

RESULTS

The primary attack rate was 45.0%, with no significant differences between sexes. The secondary attack rate during the camp stay was 22.7%. The basic reproductive number for 5 days was R0=2.62. The most frequent symptoms were abdominal pain (85.7%) and vomiting (81.9%). Epidemiological analysis showed no association with food or drinking water. A total of 66.6% (8/12) of stool samples tested positive for NV (genogroup II).

CONCLUSION

Control measures in general, and hand hygiene in particular, should be extended to the families once the children return home, to prevent secondary cases in NV outbreaks.

Risk Factors for Shiga Toxin-Producing Escherichia coli- Associated Human Diseases

We have reviewed the risk factors for the occurrence of Shiga toxin-producing Escherichia coli (STEC)-associated human diseases. The analysis of STEC surveillance data and trends shows differences in frequency and severity of the illnesses across countries, whereas the economic and social costs for the affected families, the community, and the health system are better estimated in developed countries. The occurrence of STEC infections is determined by the interaction of the pathogen, the reservoirs, and the biological, cultural, and behavioral aspects of the host. The main risk factors identified in earlier case-control and population-based studies were dietary behaviors and beef consumption. However, in recent years, other risky exposures have also emerged, like the consumption of raw vegetables and sprouts, working or camping in rural areas, visiting farms, and person-to-person transmission. Epidemiological changes have also been determined by the intensification of cattle production, the increase in centralized food production and distribution, and the growth in the volume of international trade of foods. The main lessons learned from recent large outbreaks are knowledge of virulence determinants of new pathogenic strains, recognition of new vehicles of infection, development of new methodologies for detecting STEC in foods and humans, improvement in food regulations and hygiene guidelines, new therapeutic approaches in the treatment of infected patients, establishment of continuous educational programs for food consumers, and enhanced cooperation and teamwork of regional and international networks.

Animal Reservoirs of Shiga Toxin-Producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC) strains have been detected in a wide diversity of mammals, birds, fish, and several insects. Carriage by most animals is asymptomatic, thus allowing for dissemination of the bacterium in the environment without detection. Replication of the organism may occur in the gastrointestinal tract of some animals, notably ruminants. Carriage may also be passive or transient, without significant amplification of bacterial numbers while in the animal host. Animals may be classified as reservoir species, spillover hosts, or dead-end hosts. This classification is based on the animal's ability to (i) transmit STEC to other animal species and (ii) maintain STEC infection in the absence of continuous exposure. Animal reservoirs are able to maintain STEC infections in the absence of continuous STEC exposure and transmit infection to other species. Spillover hosts, although capable of transmitting STEC to other animals, are unable to maintain infection in the absence of repeated exposure. The large diversity of reservoir and spillover host species and the survival of the organism in environmental niches result in complex pathways of transmission that are difficult to interrupt.

Barriers to Trace-back in a Salad-associated EHEC Outbreak, Sweden, June 2013

In June-July 2013, six counties notified the Swedish Institute for Communicable Disease Control of enterohaemorrhagic E.coli (EHEC) infections among attendees at a hotel in Dalarna, Sweden. An outbreak control team investigated to identify the source and implement control measures. We included individuals who attended the hotel between June 19th-25th in a cohort. We asked them about animal contact, swimming, and consumption of food items during this time using a questionnaire. A confirmed case was an EHEC O157:H7 outbreak strain positive individual who developed abdominal pain or diarrhoea between June 20th-July 2nd. We described the outbreak in time, place and person, calculated risk ratios (RR) and 95% confidence intervals (CI). We investigated the kitchen, tested and traced back implicated food items. 172 individuals responded. We identified 19 confirmed cases (Median age: 17 years, 64% female) with symptom onset between June 22nd-27th. Eating green salad on June 20th was associated with illness (RR:3.7;CI:1.3–11). The kitchen mixed green salads without records and destroyed leftovers immediately. Hence we could not conduct trace-back or obtain microbiological confirmation. Green salad contaminated before entering the kitchen was the likely outbreak source. We recommended early collaboration with food agencies and better restaurant records to facilitate future investigations.

Duration of shedding of Verocytotoxin-producing Escherichia coli in children and risk of transmission in childcare facilities in England

Exclusion of children with presumptive Verocytotoxin-producing Escherichia coli (VTEC) from childcare facilities until negative stool specimens are obtained is routine practice that disrupts families. We estimated the shedding and exclusion duration and transmission risk in such facilities. The study population comprised 225 children aged <6 years attending 201 childcare facilities in England with microbiologically confirmed VTEC in 2010-2011. We estimated the interval from onset to first negative specimen, and identified transmission events with secondary cases linked to facilities. The median duration of shedding was 31 days, and median period of exclusion was 39·5 days. Cases attending facilities while shedding VTEC did so for a median of 2 days before exclusion. Secondary cases occurred in 6/83 facilities (7%) attended by infectious cases. Despite evidence of VTEC shedding at facilities, transmission is relatively low. Revised control guidelines could consider supervised return for prolonged asymptomatic shedders.

The crystal structure of shiga toxin type 2 with bound disaccharide guides the design of a heterobifunctional toxin inhibitor

Shiga toxin type 2 (Stx2a) is clinically most closely associated with enterohemorrhagic E. coli O157:H7-mediated hemorrhagic colitis that sometimes progresses to hemolytic-uremic syndrome. The ability to express the toxin has been acquired by other Escherichia coli strains, and outbreaks of food poisoning have caused significant mortality rates as, for example, in the 2011 outbreak in northern Germany. Stx2a, an AB5 toxin, gains entry into human cells via the glycosphingolipid receptor Gb3. We have determined the first crystal structure of a disaccharide analog of Gb3 bound to the B5 pentamer of Stx2a holotoxin. In this Gb3 analog,-GalNAc replaces the terminal-Gal residue. This co-crystal structure confirms previous inferences that two of the primary binding sites identified in theB5 pentamer of Stx1 are also functional in Stx2a. This knowledge provides a rationale for the synthesis and evaluation of heterobifunctional antagonists for E. coli toxins that target Stx2a. Incorporation of GalNAc Gb3 trisaccharide in a heterobifunctional ligand with an attached pyruvate acetal, a ligand for human amyloid P component, and conjugation to poly[acrylamide-co-(3-azidopropylmethacrylamide)] produced a polymer that neutralized Stx2a in a mouse model of Shigatoxemia.

Recent advances in understanding enteric pathogenic Escherichia coli

Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic capacity to cause significant diarrheal and extraintestinal diseases. Pathogenic variants of E. coli (pathovars or pathotypes) cause much morbidity and mortality worldwide. Consequently, pathogenic E. coli is widely studied in humans, animals, food, and the environment. While there are many common features that these pathotypes employ to colonize the intestinal mucosa and cause disease, the course, onset, and complications vary significantly. Outbreaks are common in developed and developing countries, and they sometimes have fatal consequences. Many of these pathotypes are a major public health concern as they have low infectious doses and are transmitted through ubiquitous mediums, including food and water. The seriousness of pathogenic E. coli is exemplified by dedicated national and international surveillance programs that monitor and track outbreaks; unfortunately, this surveillance is often lacking in developing countries. While not all pathotypes carry the same public health profile, they all carry an enormous potential to cause disease and continue to present challenges to human health. This comprehensive review highlights recent advances in our understanding of the intestinal pathotypes of E. coli.

Photobleaching with phloxine B sensitizer to reduce food matrix interference for detection of Escherichia coli serotype O157:H7 in fresh spinach by flow cytometry

A flow cytometric method (RAPID-B™) with detection sensitivity of one viable cell of Escherichia coli serotype O157:H7 in fresh spinach (Spinacia oleracea) was developed and evaluated. The major impediment to achieving this performance was mistaking autofluorescing spinach particles for tagged target cells. Following a 5 h non-selective enrichment, artificially inoculated samples were photobleached, using phloxine B as a photosensitizer. Samples were centrifuged at high speed to concentrate target cells, then gradient centrifuged to separate them from matrix debris. In external laboratory experiments, RAPID-B and the reference method both correctly detected E. coli O157:H7 at inoculations of ca. 15 cells. In a follow-up study, after 4 cell inoculations of positives and 6 h enrichment, RAPID-B correctly identified 92% of 25 samples. The RAPID-B method limit of detection (LOD) was one cell in 25 g. It proved superior to the reference method (which incorporated real time-PCR, selective enrichment, and culture plating elements) in accuracy and speed.

Enterohemorrhagic Escherichia coli Infections and the Hemolytic-Uremic Syndrome

Enterohemorrhagic Escherichia coli (EHEC; Shiga toxin/verotoxin-producing E. coli) can cause bloody diarrhea and the hemolytic-uremic syndrome (HUS), typically following consumption of contaminated food (including ground beef, leafy greens, and sprouts) and water. Often associated with foodborne outbreaks, EHEC possess unique virulence factors that facilitate effective colonization of the human gastrointestinal tract and subsequent release of Shiga toxin. This article reviews the epidemiology, pathogenesis, clinical presentation, treatment, and prevention of EHEC infections, focusing on E. coli O157:H7, the serotype most common in North America, and E. coli O104:H4, the serotype responsible for the EHEC outbreak in Germany in 2011.

Cost-effectiveness of farm interventions for reducing the prevalence of VTEC O157 on UK dairy farms

A randomized control trial on verocytotoxigenic Escherichia coli (VTEC)-infected farms found evidence that: (1) keeping animals in the same group; (2) maintaining dry bedding; (3) preventing direct contact with neighbouring cattle; and (4) maintaining a closed herd, were associated with a reduced risk of infection in youngstock aged 3–18 months. This study evaluated these interventions using a cost-effectiveness framework for UK dairy farms. Keeping animals in the same group was considered to have negligible cost and was feasible for herds containing over 77 dairy cows. Assuming equal efficacy of the remaining interventions, preventing direct contact between neighbouring cattle is most cost-effective with a median annual cost of £2.76 per cow. This compares to £4.18 for maintaining dry bedding and £17.42 for maintaining a closed herd using quarantine procedures. Further model validation and exploration of other potential benefits are required before making policy decisions on VTEC control.

A Shiga toxin-producingEscherichia coliO157 outbreak associated with consumption of rice cakes in 2011 in Japan

In May 2011, an outbreak of Shiga toxin-producingEscherichia coli(STEC) O157 was reported from Yamagata Prefecture, Japan. Investigations, including a case-control study, revealed that the outbreak was linked to two varieties of rice cakes produced by a local manufacturer between 2 and 7 May. Active and passive surveillance identified 136 suspected cases, 142 confirmed cases, 26 asymptomatic cases, and 25 secondary cases. While no environmental samples taken from the manufacturing premises tested positive for STEC, other than a stool sample taken from one employee, on-site and epidemiological investigations indicated that STEC was introduced during the manufacturing process of rice cakes rather than through contamination of raw materials. This was the first reported outbreak of STEC associated with cakes and confectionery in Japan, which indicates that contamination and outbreaks of STEC can occur in any food unless proper precautions are taken.

Chemical structure of Retro-2, a compound that protects cells against ribosome-inactivating proteins

Shiga-like toxins and ricin are ribosome-inactivating proteins (RIPs) that are lethal to mammals and pose a global health threat. No clinical vaccines or therapeutics currently exist to protect against these RIPs. Two small molecules (Retro-1 and Retro-2) were discovered with high-throughput screening and reported for their protection of cells against RIPs. Of great significance, Retro-2, reported as (E)-2-(((5-methylthiophen-2-yl)methylene)amino)-N-phenylbenzamide, fully protected mice from lethal nasal challenge with ricin. Herein, we report studies showing that the chemical structure of Retro-2 is (±)-2-(5-methylthiophen-2-yl)-3-phenyl-2,3-dihydroquinazolin-4(1H)-one rather than (E)-2-(((5-methylthiophen-2-yl)methylene)amino)-N-phenylbenzamide. The latter is an achiral molecule that converts spontaneously to the former, which is a racemate and showed cell protection against RIPs. This calls for attention to (±)-2-(5-methylthiophen-2-yl)-3-phenyl-2,3-dihydroquinazolin-4(1H)-one as a promising RIP inhibitor and for chemical characterization of drug leads obtained from high-throughput screens.

Enteric pathogens through life stages

Enteric infections and diarrheal diseases constitute pervasive health burdens throughout the world, with rates being highest at the two ends of life. During the first 2–3 years of life, much of the disease burden may be attributed to infection with enteric pathogens including Salmonella, rotavirus, and many other bacterial, viral, and protozoan organisms; however, infections due to Clostridium difficile exhibit steady increases with age. Still others, like Campylobacter infections in industrialized settings are high in early life (<2 years old) and increase again in early adulthood (called the “second weaning” by some). The reasons for these differences undoubtedly reside in part in pathogen differences; however, host factors including the commensal intestinal microbial communities, immune responses (innate and acquired), and age-dependant shifts likely play important roles. Interplay of these factors is illustrated by studies examining changes in human gut microbiota with inflammatory bowel disease and irritable bowel syndrome. Recent gut microbial surveys have indicated dramatic shifts in gut microbial population structure from infants to young adults to the elders. An understanding of the evolution of these factors and their interactions (e.g., how does gut microbiota modulate the “inflamm-aging” process or vice versa) through the human life “cycle” will be important in better addressing and controlling these enteric infections and their consequences for both quality and quantity of life (often assessed as disability adjusted life-years or “DALYs”).

A population-based exposure assessment of risk factors associated with gastrointestinal pathogens: a Campylobacter study

A questionnaire survey was undertaken to determine the exposure of a study population to campylobacteriosis source risk factors (environmental, water, food) and results were stratified by age, population density and deprivation. Data were gathered using an exposure assessment carried out by telephone in the Grampian region of Scotland. Univariate analysis showed that children aged 5-14 years, living in low population density (0-44.4 persons/km2) and affluent areas had elevated exposure to environmental and water risk factors. Multivariate logistic regression analysis revealed that younger age groups and lower population density were significant indicators for most environmental risk factors. The results compared to reported disease incidence in Grampian showed that greater exposure to risk factors does not necessarily coincide with greater disease incidence for age groups, particularly for the 0-4 years age group. Further research is required to explain the relationship between exposure and disease incidence.

Combining risk assessment and epidemiological risk factors to elucidate the sources of humanE. coliO157 infection

E. coliO157 can be transmitted to humans by three primary (foodborne, environmental, waterborne) and one secondary (person-to-person transmission) pathways. A regression model and quantitative microbiological risk assessments (QMRAs) were applied to determine the relative importance of the primary transmission pathways in NE Scotland. Both approaches indicated that waterborne infection was the least important but it was unclear whether food or the environment was the main source of infection. The QMRAs over-predicted the number of cases by a factor of 30 and this could be because allE. coliO157 strains may not be equally infective and/or the level of infectivity in the dose–response model was too high. The efficacy of potential risk mitigation strategies to reduce human exposure toE. coliO157 using QMRAs was simulated. Risk mitigation strategies focusing on food and environment are likely to have the biggest impact on infection figures.

The relationship between lay and technical views of Escherichia coli O157 risk

Here, we bring together and contrast lay (accessible primarily through social science methodologies) and technical (via risk assessment and epidemiological techniques) views of the risk associated with the Escherichia coli O157 pathogen using two case study areas in the Grampian region of Scotland, and North Wales. Epidemiological risk factors of contact with farm animals, visiting farms or farm fields and having a private water supply were associated with postcode districts of higher than average disease incidence in the human population. However, this was not the case for the epidemiological risk factor of consumption of beef burgers, which was independent of disease incidence in the postcode district of residence. The proportion of the population expressing a high knowledge of E. coli O157 was greatest in high-incidence disease districts compared with low-incidence areas (17% cf. 7%). This supports the hypothesis that in high-disease-incidence areas, residents are regularly exposed to information about the disease through local cases, the media, local social networks, etc. or perhaps that individuals are more likely to be motivated to find out about it. However, no statistically significant difference was found between high- and low-incidence postcode districts in terms of the proportion of the population expressing a high likelihood of personal risk of infection (10% cf. 14%), giving a counterintuitive difference between the technical (epidemiological and quantitative microbiological risk assessment (QMRA)) and the lay assessment of E. coli O157 risk. This suggests that lay evaluations of E. coli O157 risk reflect intuitive and experience-based estimates of the risk rather than probabilistic estimates. A generally strong correspondence was found in terms of the rank order given to potential infection pathways, with environment and foodborne infection routes dominating when comparing public understanding with technical modelling results. Two general conclusions follow from the work. First, that integrative research incorporating both lay and technical views of risk is required in order that informed decisions can be made to handle or treat the risk by the groups concerned (e.g. the public, policy makers/risk managers, etc.). Second, when communicating risk, for example, through education programmes, it is important that this process is two-way with risk managers (e.g. including Food Standards Agency officials and communications team, public health infection control and environmental health officers) both sharing information with the public and stakeholder groups, as well as incorporating public knowledge, values and context (e.g. geographical location) into risk-management decisions.

Escherichia coli O157 infection and secondary spread, Scotland, 1999-2008

To determine the proportion of Escherichia coli O157 cases in Scotland attributable to secondary spread, we analyzed data obtained through entire-population enhanced surveillance. We identified 11% of cases as secondary. Secondary cases in single households were younger than secondary cases in outbreaks affecting >1 household and had similar risk for hemolytic uremic syndrome.