Shiga toxin-producing Escherichia coli haemolytic uraemic syndrome (STEC-HUS): diagnosis, surveillance and public-health management in England

Genomic analysis of an outbreak of Shiga toxin-producing Escherichia coli O183:H18 in the United Kingdom, 2023

In June 2023, UKHSA surveillance systems detected an outbreak of severe gastrointestinal symptoms caused by a rare serotype of Shiga toxin-producing Escherichia coli, STEC O183:H18. There were 26 cases aged 6 months to 74 years (42 % cases were aged 0-9 years), distributed across the UK with onset dates range between 22 May 2023 and 4 July 2023. The epidemiological and food chain investigations were inconclusive, although meat products made from beef mince were implicated as a potential vehicle. The outbreak strain belonged to sequence type (ST) 657 and harboured a Shiga toxin (stx) subtype stx2a located on a prophage that was unique in the UKHSA stx-encoding bacteriophage database. Plasmid encoded, putative virulence genes subA, ehxA, saa, iha, lpfA and iss were detected, however, the established STEC virulence genes involved in attachment to the gut mucosa (eae and aggR) were absent. The acquisition of stx across the global population structure of ST657 appeared to correspond with the presence of subA, ehxA, saa, iha, lpfA and iss. During the outbreak investigation, we used long read sequencing to characterise the plasmid and prophage content of this atypical STEC, to look for evidence to explain its recent emergence. Although we were unable to determine source and transmission route of the outbreak strain, the genomic analysis revealed potential clues as to how novel strains for STEC evolve. With the implementation of PCR capable of detecting all STEC, and genome sequencing for typing and virulence profiling, we have the tools to enable us to monitor the changing landscape of STEC. Improvements in the standardised collection of epidemiological data and trace-back strategies within the food industry, will ensure we have a surveillance system capable of alerting us to emerging threats to public health.

How We Interpret Thrombosis with Thrombocytopenia Syndrome?

Platelets play an important role in hemostasis, and a low platelet count usually increases the risk of bleeding. Conditions in which thrombosis occurs despite low platelet counts are referred to as thrombosis with thrombocytopenia syndrome, including heparin-induced thrombocytopenia, vaccine-induced immune thrombotic thrombocytopenia, paroxysmal nocturnal hemoglobinuria, antiphospholipid syndrome, thrombotic microangiopathy (TMA), and disseminated intravascular coagulation. TMA includes thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (HUS), and atypical HUS. Patients with these pathologies present with thrombosis and consumptive thrombocytopenia associated with the activation of platelets and the coagulation system. Treatment varies from disease to disease, and many diseases have direct impacts on mortality and organ prognosis if therapeutic interventions are not promptly implemented. Underlying diseases and the results of physical examinations and general laboratory tests as part of a thorough workup for patients should promptly lead to therapeutic intervention before definitive diagnosis. For some diseases, the diagnosis and initial treatment must proceed in parallel. Utilization of not only laboratory tests but also various scoring systems is important for validating therapeutic interventions based on clinical information.

Clinical and public health implications of increasing notifications of LEE-negative Shiga toxin-producing Escherichia coli in England, 2014-2022

Introduction. Shiga toxin-producing Escherichia coli (STEC) belong to a diverse group of gastrointestinal pathogens. The pathogenic potential of STEC is enhanced by the presence of the pathogenicity island called the Locus of Enterocyte Effacement (LEE), including the intimin encoding gene eae.Gap statement. STEC serotypes O128:H2 (Clonal Complex [CC]25), O91:H14 (CC33), and O146:H21 (CC442) are consistently in the top five STEC serotypes isolated from patients reporting gastrointestinal symptoms in England. However, they are eae/LEE-negative and perceived to be a low risk to public health, and we know little about their microbiology and epidemiology.Aim. We analysed clinical outcomes and genome sequencing data linked to patients infected with LEE-negative STEC belonging to CC25 (O128:H2, O21:H2), CC33 (O91:H14) and, and CC442 (O146:H21, O174:H21) in England to assess the risk to public health.Results. There was an almost ten-fold increase between 2014 and 2022 in the detection of all STEC belonging to CC25, CC33 and CC442 (2014 n=38, 2022 n=336), and a total of 1417 cases. There was a higher proportion of female cases (55-70 %) and more adults than children, with patients aged between 20-40 and >70 most at risk across the different serotypes. Symptoms were consistent across the three dominant serotypes O91:H14 (CC33), O146:H21 (CC442) and O128:H2 (CC25) (diarrhoea >75 %; bloody diarrhoea 25-32 %; abdominal pain 64-72 %; nausea 37-45 %; vomiting 10-24 %; and fever 27-30 %). Phylogenetic analyses revealed multiple events of acquisition and loss of different stx-encoding prophage. Additional putative virulence genes were identified including iha, agn43 and subA.Conclusions. Continued monitoring and surveillance of LEE-negative STEC infections is essential due to the increasing burden of infectious intestinal disease, and the risk that highly pathogenic strains may emerge following acquisition of the Shiga toxin subtypes associated with the most severe clinical outcomes.

Haemolytic uraemic syndrome in children England, Wales, Northern Ireland, and Ireland: A prospective cohort study

Haemolytic uraemic syndrome (HUS) caused by infection with Shiga toxin-producing Escherichia coli (STEC) is a relatively rare but potentially fatal multisystem syndrome clinically characterised by acute kidney injury. This study aimed to provide robust estimates of paediatric HUS incidence in England, Wales, Northern Ireland, and the Republic of Ireland by using data linkage and case reconciliation with existing surveillance systems, and to describe the characteristics of the condition. Between 2011 and 2014, 288 HUS patients were included in the study, of which 256 (89.5%) were diagnosed as typical HUS. The crude incidence of paediatric typical HUS was 0.78 per 100,000 person-years, although this varied by country, age, gender, and ethnicity. The majority of typical HUS cases were 1 to 4 years old (53.7%) and female (54.0%). Clinical symptoms included diarrhoea (96.5%) and/or bloody diarrhoea (71.9%), abdominal pain (68.4%), and fever (41.4%). Where STEC was isolated (59.3%), 92.8% of strains were STEC O157 and 7.2% were STEC O26. Comparison of the HUS case ascertainment to existing STEC surveillance data indicated an additional 166 HUS cases were captured during this study, highlighting the limitations of the current surveillance system for STEC for monitoring the clinical burden of STEC and capturing HUS cases.

The epidemiology of Shiga toxin-producing Escherichia coli O26:H11 (clonal complex 29) in England, 2014-2021

OBJECTIVES

We aimed to describe the genomic epidemiology of the foodborne gastrointestinal pathogen, Shiga toxin-producing Escherichia coli (STEC) serotype O26:H11 belonging to clonal complex 29 (CC29) in England.

METHODS

Between 01 January 2014 and 31 December 2021, 834 human isolates belonging to CC29 were sequenced at the UK Health Security Agency, and the genomic data was integrated with epidemiological data.

RESULTS

Diagnoses of STEC O26:H11 in England have increased each year from 19 in 2014 to 144 in 2021. Most isolates had the Shiga toxin subtype profiles stx1a (47%), stx1a,stx2a (n=24%) or stx2a (n=28%). Most cases were female (57%), and the highest proportion of cases belonged to the 0-5 age group (38%). Clinical symptoms included diarrhoea (93%), blood-stained stool (48%), and abdominal pain (74%). Haemolytic Uraemic Syndrome (HUS) was diagnosed in 40/459 (9%) cases and three children died. All isolates causing STEC-HUS had stx2a either alone (n=33) or in combination with stx1a (n=7).

CONCLUSIONS

STEC O26:H11 are a clinically significant, emerging threat to public health in England. Determining the true incidence and prevalence is challenging due to inconsistent national surveillance strategies. Improved diagnostics and surveillance algorithms are required to monitor the true burden, detect outbreaks and to implement effective interventions.

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.

Two Outbreaks of Foodborne Gastrointestinal Infection Linked to Consumption of Imported Melons, United Kingdom, March to August 2021

The aim of this study was to describe two foodborne outbreaks caused by contaminated imported melon and make recommendations for future practice. Between March and July 2021, there was an outbreak of 113 cases of Salmonella Braenderup in the UK (62% female, median age 61 years, 33% hospitalized). Analytical epidemiological studies identified Galia melons as the vehicle of infection (OR 671.9, 95% CI 39.0-58,074.0, p < 0.001). Subsequently, the outbreak strain was isolated from two samples of Galia melon imported from Latin America. In July and August 2021, there was an outbreak of 17 cases of Shiga toxin-producing Escherichia coli (STEC) O157:H7 in the UK (53% female, median age 21 years, 35% were hospitalized). Review of the STEC surveillance questionnaire data, followed by the analysis of responses from a modified hypothesis-generating questionnaire, implicated eating precut watermelon from retailer B sourced from Europe as the vehicle of infection. Outbreaks of gastrointestinal pathogens caused by contaminated food of nonanimal origin are a global public health concern. Given the difficulty in removing pathogens from the flesh of ready-to-eat fruit and vegetables, public health interventions should target all steps of the food chain prior to consumption, from cultivation on the farm to processing/packing and distribution.

Diagnosis and Treatment for Shiga Toxin-Producing Escherichia coli Associated Hemolytic Uremic Syndrome

Shiga toxin-producing Escherichia coli (STEC)-associated hemolytic uremic syndrome (STEC-HUS) is a clinical syndrome involving hemolytic anemia (with fragmented red blood cells), low levels of platelets in the blood (thrombocytopenia), and acute kidney injury (AKI). It is the major infectious cause of AKI in children. In severe cases, neurological complications and even death may occur. Treating STEC-HUS is challenging, as patients often already have organ injuries when they seek medical treatment. Early diagnosis is of great significance for improving prognosis and reducing mortality and sequelae. In this review, we first briefly summarize the diagnostics for STEC-HUS, including history taking, clinical manifestations, fecal and serological detection methods for STEC, and complement activation monitoring. We also summarize preventive and therapeutic strategies for STEC-HUS, such as vaccines, volume expansion, renal replacement therapy (RRT), antibiotics, plasma exchange, antibodies and inhibitors that interfere with receptor binding, and the intracellular trafficking of the Shiga toxin.

Outbreak of STEC O157:H7 linked to a milk pasteurisation failure at a dairy farm in England, 2019

In November 2019, an outbreak of Shiga toxin-producing Escherichia coli O157:H7 was detected in South Yorkshire, England. Initial investigations established consumption of milk from a local dairy as a common exposure. A sample of pasteurised milk tested the next day failed the phosphatase test, indicating contamination of the pasteurised milk by unpasteurised (raw) milk. The dairy owner agreed to immediately cease production and initiate a recall. Inspection of the pasteuriser revealed a damaged seal on the flow divert valve. Ultimately, there were 21 confirmed cases linked to the outbreak, of which 11 (52%) were female, and 12/21 (57%) were either <15 or >65 years of age. Twelve (57%) patients were treated in hospital, and three cases developed haemolytic uraemic syndrome. Although the outbreak strain was not detected in the milk samples, it was detected in faecal samples from the cattle on the farm. Outbreaks of gastrointestinal disease caused by milk pasteurisation failures are rare in the UK. However, such outbreaks are a major public health concern as, unlike unpasteurised milk, pasteurised milk is marketed as ‘safe to drink’ and sold to a larger, and more dispersed, population. The rapid, co-ordinated multi-agency investigation initiated in response to this outbreak undoubtedly prevented further cases.

Epidemiological investigations identified an outbreak of Shiga toxin-producing Escherichia coli serotype O26:H11 associated with pre-packed sandwiches

In October 2019, public health surveillance systems in Scotland identified an increase in the number of reported infections of Shiga toxin-producing Escherichia coli (STEC) O26:H11 involving bloody diarrhoea. Ultimately, across the United Kingdom (UK) 32 cases of STEC O26:H11 stx1a were identified, with the median age of 27 years and 64% were male; six cases were hospitalised. Among food exposures there was an association with consuming pre-packed sandwiches purchased at outlets belonging to a national food chain franchise (food outlet A) [odds ratio (OR) = 183.89, P < 0.001]. The common ingredient identified as a component of the majority of the sandwiches sold at food outlet A was a mixed salad of Apollo and Iceberg lettuce and spinach leaves. Microbiological testing of food and environmental samples were negative for STEC O26:H11, although STEC O36:H19 was isolated from a mixed salad sample taken from premises owned by food outlet A. Contamination of fresh produce is often due to a transient event and detection of the aetiological agent in food that has a short-shelf life is challenging. Robust, statistically significant epidemiological analysis should be sufficient evidence to direct timely and targeted on-farm investigations. A shift in focus from testing the microbiological quality of the produce to investigating the processes and practices through the supply chain and sampling the farm environment is recommended.

Epidemiological investigation of recurrent outbreaks of haemolytic uraemic syndrome caused by Shiga toxin-producing Escherichia coli serotype O55:H7 in England, 2014-2018

Recurrent outbreaks of haemolytic uraemic syndrome (HUS) caused by Shiga toxin-producing Escherichia coli (STEC) serotype O55:H7 occurred in England between 2014 and 2018. We reviewed the epidemiological evidence to identify potential source(s) and transmission routes of the pathogen, and to assess the on-going risk to public health. Over the 5-year period, there were 43 confirmed and three probable cases of STEC O55:H7. The median age of cases was 4 years old (range 6 months to 69 years old) and over half of all cases were female (28/46, 61%). There were 36/46 (78.3%) symptomatic cases, and over half of all cases developed HUS (25/46, 54%), including two fatal cases. No common food or environmental exposures were identified, although the majority of cases lived in rural or semi-rural environments and reported contact with both wild and domestic animals. This investigation informed policy on the clinical and public health management of HUS caused by STEC other than serotype O157:H7 (non-O157 STEC) in England, including comprehensive testing of all household contacts and household pets and more widespread use of polymerase chain reaction assays for the rapid diagnosis of STEC-HUS.

Comparison of Common Enrichment Broths Used in Diagnostic Laboratories for Shiga Toxin-Producing Escherichia coli

Acute gastroenteritis caused by Shiga toxin-producing Escherichia coli (STEC) affects more than 4 million individuals in Canada. Diagnostic laboratories are shifting towards culture-independent diagnostic testing; however, recovery of STEC remains an important aspect of surveillance programs. The objective of this study was to compare common broth media used for the enrichment of STEC. Clinical isolates including O157:H7 as well as non-O157 serotypes were cultured in tryptic soy (TSB), MacConkey (Mac), and Gram-negative (GN) broths and growth was compared using culture on sheep’s blood agar and real-time PCR (qPCR). In addition, a selection of the same isolates was spiked into negative stool and enriched in the same three broths, which were then evaluated using culture on CHROMagar^TM STEC agar and qPCR. TSB was found to provide the optimal enrichment for growth of isolates with and without stool. The results from this study suggest that diagnostic laboratories may benefit from enriching STEC samples in TSB as a first line enrichment instead of GN or Mac.

Phylogenetic context of Shiga toxin-producing Escherichia coli serotype O26:H11 in England

The increasing use of PCR for the detection of gastrointestinal pathogens in hospital laboratories in England has improved the detection of Shiga toxin-producing Escherichia coli (STEC), and the diagnosis of haemolytic uraemic syndrome (HUS). We aimed to analyse the microbiological characteristics and phylogenetic relationships of STEC O26:H11, clonal complex (CC) 29, in England to inform surveillance, and to assess the threat to public health. There were 502 STEC belonging to CC29 isolated between 2014 and 2019, of which 416 were from individual cases. The majority of isolates belonged to one of three major sequence types (STs), ST16 (n=37), ST21 (n=350) and ST29 (n=24). ST16 and ST29 were mainly isolated from cases reporting recent travel abroad. Within ST21, there were three main clades associated with domestic acquisition. All three domestic clades had Shiga toxin subtype gene (stx) profiles associated with causing severe clinical outcomes including STEC-HUS, specifically either stx1a, stx2a or stx1a/stx2a. Isolates from the same patient, same household or same outbreak with an established source for the most part fell within 5-SNP single linkage clusters. There were 19 5-SNP community clusters, of which six were travel-associated and one was an outbreak of 16 cases caused by the consumption of contaminated salad leaves. Of the remaining 12 clusters, 9/12 were either temporally or geographically related or both. Exposure to foodborne STEC O26:H11 ST21 capable of causing severe clinical outcomes, including STEC-HUS, is an emerging risk to public health in England. The lack of comprehensive surveillance of this STEC serotype is a concern, and there is a need to expand the implementation of methods capable of detecting STEC in local hospital settings.