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

Detection of prolong excretion of Escherichia albertii in stool specimens of a 7-year-old child by a newly developed Eacdt gene-based quantitative real-time PCR method and molecular characterization of the isolates

Escherichia albertii is an emerging zoonotic foodborne pathogen. The clinical significance of this bacterium has increasingly been recognized worldwide. However, diagnostic method has not yet been established and its clinical manifestations are not fully understood. Here, we show that an Eacdt gene-based quantitative real-time PCR (qRT-PCR) developed in this study is 100% specific and sensitive when tested with 39 E. albertii and 36 non-E. albertii strains, respectively. Detection limit of the real-time PCR was 10 colony forming unit (CFU) and 1 pg of genomic DNA per PCR tube. When E. albertii was spiked with 4 × 100-106 CFU per mL to stool of healthy person, detection limit was 4.0 × 103 and 4.0 CFU per mL before and after enrichment culture, respectively. Moreover, the qRT-PCR was able to detect E. albertii in five children out of 246 (2%) but none from 142 adults suffering from gastroenteritis. All five E. albertii strains isolated carried eae and paa genes, however, only one strain harbored stx2f genes. Long-term shedding of stx2f gene-positive E. albertii in a child stool could be detected because of the qRT-PCR developed in this study which might have been missed if only conventional PCR and culture methods were employed. Furthermore, E. albertii isolated from siblings with diarrhea showed clonality by PFGE analysis. Taken together, these data suggest that the Eacdt gene-based qRT-PCR developed for the detection of E. albertii is useful and will assist in determining the real burden and clinical manifestation of E. albertii infections.

Do asymptomatic STEC-long-term carriers need to be isolated or decolonized? New evidence from a community case study and concepts in favor of an individualized strategy

Asymptomatic long-term carriers of Shigatoxin producing Escherichia coli (STEC) are regarded as potential source of STEC-transmission. The prevention of outbreaks via onward spread of STEC is a public health priority. Accordingly, health authorities are imposing far-reaching restrictions on asymptomatic STEC carriers in many countries. Various STEC strains may cause severe hemorrhagic colitis complicated by life-threatening hemolytic uremic syndrome (HUS), while many endemic strains have never been associated with HUS. Even though antibiotics are generally discouraged in acute diarrheal STEC infection, decolonization with short-course azithromycin appears effective and safe in long-term shedders of various pathogenic strains. However, most endemic STEC-strains have a low pathogenicity and would most likely neither warrant antibiotic decolonization therapy nor justify social exclusion policies. A risk-adapted individualized strategy might strongly attenuate the socio-economic burden and has recently been proposed by national health authorities in some European countries. This, however, mandates clarification of strain-specific pathogenicity, of the risk of human-to-human infection as well as scientific evidence of social restrictions. Moreover, placebo-controlled prospective interventions on efficacy and safety of, e.g., azithromycin for decolonization in asymptomatic long-term STEC-carriers are reasonable. In the present community case study, we report new observations in long-term shedding of various STEC strains and review the current evidence in favor of risk-adjusted concepts.

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.

Detection of plasma anti-lipopolysaccharide (LPS) antibodies against enterohemorrhagic Escherichia coli (EHEC) in asymptomatic kindergarten teachers from Buenos Aires province

In Argentina, hemolytic uremic syndrome (HUS) caused by EHEC has the highest incidence in the world. EHEC infection has an endemo-epidemic behavior, causing 20-30% of acute bloody diarrhea syndrome in children under 5 years old. In the period 2016-2020, 272 new cases per year were notified to the National Health Surveillance System. Multiple factors are responsible for HUS incidence in Argentina including person-to-person transmission. In order to detect possible EHEC carriers, we carried out a preliminary study of the frequency of kindergarten teachers with anti-LPS antibodies against the most prevalent EHEC serotypes in Argentina. We analyzed 61 kindergarten teachers from 26 institutions from José C. Paz district, located in the suburban area of Buenos Aires province, Argentina. Fifty-one percent of the plasma samples had antibodies against O157, O145, O121 and O103 LPS: 6.4% of the positive samples had IgM isotype (n=2), 61.3% IgG isotype (n=19) and 32.3% IgM and IgG (n=10). Given that antibodies against LPS antigens are usually short-lived specific IgM detection may indicate a recent infection. In addition, the high percentage of positive samples may indicate a frequent exposure to EHEC strains in the cohort studied, as well as the existence of a large non-symptomatic population of adults carrying pathogenic strains that could contribute to the endemic behavior through person-to-person transmission. The improvement of continuous educational programs in kindergarten institutions could be a mandatory measure to reduce HUS cases not only in Argentina but also globally.

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.

Shiga toxin-producing Escherichia coli (STEC) shedding in a wild roe deer population

Worldwide infections by Shiga toxin-producing Escherichia coli (STEC) in humans have been reported after consumption of mainly beef, but also deer meat. Not only the consumption of contaminated deer meat represents a risk, but also the transmission of STEC between deer and domestic animals should be considered. Within the framework of a telemetry study of roe deer (Capreolus capreolus) the aim was to analyse the occurrence of STEC. Due to the chance to sample some animals several times it was possible to obtain data on the repeated shedding of STEC in roe deer. In total 124 faeces or rectal swabs of 77 live trapped roe deer were collected. The isolates obtained were characterized for stx subtypes, different virulence genes, the so-called top-five serogroups, phylogenetic groups, PFGE-types and antimicrobial susceptibilities. The majority of roe deer were stx-positive whenever sampled. Twenty-eight animals were sampled more than once and were used to examine the duration of shedding STEC. The time interval of 6 persistently stx-negative tested animals was between 6 and 440d (median 49d, interquartile range (IQR) 17-258d). Ten animals excreted undistinguishable STEC strains in intervals between 4 and 778d (median 42d, IQR 22-79d). Most of the isolates were stx2b-positive, eae-negative and frequently ehlyA-positive. None of the isolates belonged to serogroup O26, O103, O111, O145 and O157, respectively. All isolates were sensitive to the antimicrobial substances tested. Although the duration of each shedding event could not be determined the results indicate long-term excretion of STEC in roe deer. This is an important consideration for the observance of good hygiene practice while field dressing of deer and preparing deer meat.

Mapping of control measures to prevent secondary transmission of STEC infections in Europe during 2016 and revision of the national guidelines in Norway

In 2016, we reviewed preventive control measures for secondary transmission of Shiga-toxin producing Escherichia coli (STEC) in humans in European Union (EU)/European Free Trade Association (EEA) countries to inform the revision of the respective Norwegian guidelines which at that time did not accommodate for the varying pathogenic potential of STEC. We interviewed public health experts from EU/EEA institutes, using a semi-structured questionnaire. We revised the Norwegian guidelines using a risk-based approach informed by the new scientific evidence on risk factors for HUS and the survey results. All 13 (42%) participating countries tested STEC for Shiga toxin (stx) 1, stx2 and eae (encoding intimin). Five countries differentiated their control measures based on clinical and/or microbiological case characteristics, but only Denmark based their measures on routinely conducted stx subtyping. In all countries, but Norway, clearance was obtained with ⩽3 negative STEC specimens. After this review, Norway revised the STEC guidelines and recommended only follow-up of cases infected with high-virulent STEC (determined by microbiological and clinical information); clearance is obtained with three negative specimens. Implementation of the revised Norwegian guidelines will lead to a decrease of STEC cases needing follow-up and clearance, and will reduce the burden of unnecessary public health measures and the socioeconomic impact on cases. This review of guidelines could assist other countries in adapting their STEC control measures.

Shiga toxin-producing Escherichia coli in British Columbia, 2011-2017: Analysis to inform exclusion guidelines

Background

Shiga toxin-producing Escherichia coli (STEC) can cause severe illness including bloody diarrhea and hemolytic-uremic syndrome (HUS) through the production of Shiga toxins 1 (Stx1) and 2 (Stx2). E. coli O157:H7 was the most common serotype detected in the 1980s to 1990s, but improvements in laboratory methods have led to increased detection of non-O157 STEC. Non-O157 STEC producing only Stx1 tend to cause milder clinical illness. Exclusion guidelines restrict return to high-risk work or settings for STEC cases, but most do not differentiate between STEC serogroups and Stx type.

Objective

To analyze British Columbia (BC) laboratory and surveillance data to inform the BC STEC exclusion guideline.

Methods

For all STEC cases reported in BC in 2011-2017, laboratory and epidemiological data were obtained through provincial laboratory and reportable disease electronic systems, respectively. Incidence was measured for all STEC combined as well as by serogroup. Associations were measured between serogroups, Stx types and clinical outcomes.

Results

Over the seven year period, 984 cases of STEC were reported. A decrease in O157 incidence was observed, while non-O157 rates increased. The O157 serogroup was significantly associated with Stx2. Significant associations were observed between Stx2 and bloody diarrhea, hospitalization and HUS.

Conclusion

The epidemiology of STEC has changed in BC as laboratories increasingly distinguish between O157 and non-O157 cases and identify Stx type. It appears that non-O157 cases with Stx1 are less severe than O157 cases with Stx2. The BC STEC exclusion guidelines were updated as a result of this analysis.

Evaluation of the impact of shigellosis exclusion policies in childcare settings upon detection of a shigellosis outbreak

Background

In the event of a shigellosis outbreak in a childcare setting, exclusion policies are typically applied to afflicted children to limit shigellosis transmission. However, there is scarce evidence of their impact.

Methods

We evaluated five exclusion policies: Children return to childcare after: i) two consecutive laboratory tests (either PCR or culture) do not detect Shigella, ii) a single negative laboratory test (PCR or culture) does not detect Shigella, iii) seven days after beginning antimicrobial treatment, iv) after being symptom-free for 24 h, or v) 14 days after symptom onset. We also included four treatments to assess the policy options: i) immediate, effective treatment; ii) effective treatment after laboratory diagnosis; iii) no treatment; iv) ineffective treatment. Relying on published data, we calculated the likelihood that a child reentering childcare would be infectious, and the number of childcare-days lost per policy.

Results

Requiring two consecutive negative PCR tests yielded a probability of onward transmission of < 1%, with up to 17 childcare-days lost for children receiving effective treatment, and 53 days lost for those receiving ineffective treatment.

Conclusions

Of the policies analyzed, requiring negative PCR testing before returning to childcare was the most effective to reduce the risk of shigellosis transmission, with one PCR test being the most effective for the least childcare-days lost.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3796-7) contains supplementary material, which is available to authorized users.

Shiga Toxin (Verotoxin)-producing Escherichia coli and Foodborne Disease: A Review

Shiga toxin (verotoxin)-producing Escherichia coli (STEC) is an important cause of foodborne disease. Since outcomes of the infections with STEC have a broad range of manifestation from asymptomatic infection or mild intestinal discomfort, to bloody diarrhea, hemolytic uremic syndrome (HUS), end-stage renal disease (ESRD), and death, the disease is a serious burden in public health and classified as a notifiable infectious disease in many countries. Cattle and other ruminants are considered to be the major reservoirs of STEC though isolation of STEC from other animals have been reported. Hence, the source of contamination extends to a wide range of foods, not only beef products but also fresh produce, water, and environment contaminated by excretes from the animals, mainly cattle. A low- infectious dose of STEC makes the disease relatively contagious, and causes outbreaks with unknown contamination sources and, therefore, as a preventive measure against STEC infection, it is important to obtain characteristics of prevailing STEC isolates in the region through robust surveillance. Analysis of the isolates by pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA) could help finding unrecognized foodborne outbreaks due to consumption of respective contaminated sources. However, though the results of molecular analysis of the isolates could indicate linkage of sporadic cases of STEC infection, it is hardly concluded that the cases are related via contaminated food source if it were not for epidemiological information. Therefore, it is essential to combine the results of strain analysis and epidemiological investigation rapidly to detect rapidly foodborne outbreaks caused by bacteria. This article reviews STEC infection as foodborne disease and further discusses key characteristics of STEC including pathogenesis, clinical manifestation, prevention and control of STEC infection. We also present the recent situation of the disease in Japan based on the surveillance of STEC infection.

A 10-year analysis of VTEC microbiological clearance times, in the under-six population of the Midlands, Ireland

Verotoxin-producingEscherichia coli(VTEC) is a significant problem in the under-six population in the Midlands, Ireland. VTEC spreads by person-to-person transmission and children attending childcare facilities are excluded until they achieve two consecutive negative stool samples. This report analyses 10 years data on the number of days children under the age of six take to microbiologically clear VTEC. We identified from our data that the median clearance time for VTEC was 39 days, interquartile range (IQR) 27–56 days, maximum clearance time 283 days. At 70 days from onset of infection, 90% of children had cleared the infection. These findings were slightly more prolonged but consistent with international literature on VTEC clearance times for children. Asymptomatic children cleared VTEC infection significantly faster (median time 25 days IQR 13–43 days) than symptomatic children (median time 43 days IQR 31–58 days). Symptomatic children older than 1 year of age cleared VTEC infection significantly faster (median time 42 days IQR 31–57) than symptomatic children year under 1 year (median time 56 days IQR 35–74 days). This report identifies clear data which can be used to more accurately advise parents on time periods required to achieve microbiological clearance from VTEC.

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.

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.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0673-2) contains supplementary material, which is available to authorized users.

The utility and public health implications of PCR and whole genome sequencing for the detection and investigation of an outbreak of Shiga toxin-producingEscherichia coliserogroup O26:H11

Many serogroups of Shiga toxin-producingEscherichia coli(STEC) other than serogroup O157 (non-O157 STEC), for example STEC O26:H11, are highly pathogenic and capable of causing haemolytic uraemic syndrome. A recent increase in non-O157 STEC cases identified in England, resulting from a change in the testing paradigm, prompted a review of the current methods available for detection and typing of non-O157 STEC for surveillance and outbreak investigations. Nineteen STEC O26:H11 strains, including four from a nursery outbreak were selected to assess typing methods. Serotyping and multilocus sequence typing were not able to discriminate between thestx-producing strains in the dataset. However, genome sequencing provided rapid and robust confirmation that isolates of STEC O26:H11 associated with a nursery outbreak were linked at the molecular level, had a common source and were distinct from the other strains analysed. Virulence gene profiling of DNA extracted from a polymerase chain reaction (PCR)-positive/culture-negative faecal specimen from a case that was epidemiologically linked to the STEC O26:H11 nursery outbreak, provided evidence at the molecular level to support that link. During this study, we describe the utility of PCR and the genome sequencing approach in facilitating surveillance and enhancing the response to outbreaks of non-O157 STEC.