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Factsheet for health professionals on Shiga toxin-producing Escherichia coli (STEC) infection

Factsheet

Last reviewed/updated: 22 August 2024

Disclaimer: The information contained in this factsheet is intended for the purpose of general information and should not substitute individual expert advice or judgement of healthcare professionals.

Case definition 

Shiga toxin-producing Escherichia coli (STEC) infection is notifiable in the EU. The European case definition is available here.

The pathogen

Shiga toxin producing Escherichia coli (STEC), also known as verotoxigenic, verocytotoxigenic, verotoxin-producing, verocytotoxin-producing E. coli (VTEC) or Enterohemorrhagic E. coli (EHEC), is a subset of pathogenic bacterium E. coli. It carries genes that can produce the Shiga toxins, stx1 with four subtypes (a, c, d and e), and stx2, with 15 subtypes (a to o) recently described [1]. These toxins particularly affect small blood vessels, such as those found in the digestive tract and the kidneys. The outcome of infection is dependent on several factors, including the stx subtype. Although all STEC strains are potentially pathogenic in humans and capable of causing diarrhoea, serious illness with bloody diarrhoea and haemolytic-uremic syndrome (HUS) is more often associated with STEC that carry stx2 genes − in particular the stx2a or stx2d subtypes [2,3]. This highlights the importance of subtyping the Shiga toxin genes in clinical cases.

In Europe, five serogroups (O157, O26, O111, O103 and O145) are associated with the majority of severe cases in humans [3]. Although a recent pathogenicity assessment of STEC affirms that serogroup is not a marker of pathogenicity, data can be useful for identifying STEC and to observe the circulation of the different STEC serogroups in food and human cases [2].

Clinical features and sequelae

STEC infection causes gastroenteritis, accompanied by stomach cramps, abdominal pain, vomiting, and diarrhoea, which is often bloody. The incubation period is from three to eight days after exposure. The infective dose of STEC is low: thought to be fewer than 100 bacteria. Gastroenteritis symptoms vary from asymptomatic to severe haemorrhagic enterocolitis. Most cases recover within five to seven days, however long-term shedding of STEC has been detected in asymptomatic carriers after the initial infection. STEC infections affect people of all ages, however children and the elderly are at higher risk of severe disease and complications [3,4]. A potentially life-threatening complication known as haemolytic-uremic syndrome (HUS), a progressive kidney failure can develop after gastroenteritis symptoms. The mortality rate for HUS is 3−20% [4]. Chronic kidney disease can follow an acute episode of HUS, with hypertension, proteinuria, and a reduced glomerular filtration rate.

Epidemiology 

STEC has been the third most-commonly-reported gastrointestinal food- and waterborne disease in the EU/EEA and also the third most frequent bacterial pathogen detected in foodborne outbreaks in the EU. The majority of the cases are acquired in the EU/EEA [3]. 

The latest information on the epidemiological situation is presented in ECDC annual epidemiological reports and the EU One Health Zoonoses reports.

Transmission

The main reservoir of STEC is ruminants, in particular cattle, but several other wild and domestic animals can carry the pathogen. Cattle can persistently carry STEC without symptomatic colonisation and shed the pathogen in their faeces [5]. The majority of STEC infections are foodborne and regularly associated with the consumption of undercooked beef which has been contaminated during slaughter [6]. Raw milk, cheese and other dairy products made from unpasteurised milk are also possible sources of infection. Contaminated water can be a source of infection, directly or through irrigation water which pollutes fresh produce (fruit and vegetables). 

Direct contact with carrier animals or their faecal material, for example at petting farms and zoos, is considered to represent an important risk of STEC, particularly among children [7].

Person-to-person transmission of STEC is rare but possible, in direct contact with an STEC carrier, as well as during sexual intercourse [8]. In childcare settings, secondary cases via human-to-human spread during outbreaks involving diarrhoea are commonly reported [9]. Asymptomatic long-term carriers of STEC are regarded as a potential source of STEC-transmission, although their role in transmission is unclear [10].

Diagnostics 

Testing for STEC may include selective culture methods and/or molecular methods [11]. Human STEC infections are generally diagnosed by culture from stool samples and in the event of HUS cases, through the indirect detection of antibodies against the O-lipopolysaccharides from E. coli in serum for specific serotypes. Diagnosis also often involves identifying the presence of stx genes in stools using polymerase chain reaction (PCR) without strain isolation. The range of molecular methods available for screening, detecting, confirming and/or characterising STEC includes several PCR-based genetic methods, usually targeting stx genes and whole genome sequencing (WGS). WGS has been used for the genomic surveillance of STEC for public health purposes, via the tracking of outbreaks [12].

In order to meet the case definition for a confirmed case in accordance with the EU case definition, microbiological confirmation is necessary.

Case management and treatment 

There is no specific treatment for STEC infection; treatment focuses on symptomatic and supportive care. Treatment involves replacing lost fluids and keeping patients hydrated. Antibiotics are not generally advised as they could cause more severe illness and increase the risk of developing HUS [13].

Public health prevention and control measures (for the authorities)

STEC infection is mainly acquired through the consumption of contaminated food or water and contact with infected animals and/or their faeces. Bacteria are transmitted via the faecal-oral route. Good hygiene practices during the food processing and retail stage of the food chain, as well as good handling practices in premises dealing with animals (farms, slaughterhouses) can decrease the risk of contamination of food and infection for people handling animals, [2,14]. Guidance on hand hygiene and facilities for hand washing should be available for visitors to petting farms and zoos and adults should ensure that younger children in particular follow these rules [15]. The general principles of food hygiene and handling [16] will be effective in preventing STEC infections at home (i.e. adequate cooking of foods such as beef and the use of pasteurised dairy products, proper washing and peeling of vegetables and avoiding cross contamination from raw to cooked food) in order to reduce the risk of foodborne STEC infections. 

Infection control, personal protection and prevention (for the health facilities)

Routine hygiene measures, including proper hand and toilet hygiene, are sufficient for the general control of STEC infections to prevent human-to-human spread. Specific infection prevention measures, such as sanitary separation of patients in healthcare settings during episodes of diarrhoea, may be necessary, particularly among risk groups (children, the immunocompromised and the elderly) and in situations where the patient is not able to comply with the recommended hygiene measures (e.g. due to age). 

Health professionals should follow national guidelines and recommendations for STEC infection prevention and control as the primary source of information.

References

  1. Lindsey RL, Prasad A, Feldgarden M, Gonzalez-Escalona N, Kapsak C, Klimke W, et al. Identification and Characterization of ten Escherichia coli Strains Encoding Novel Shiga Toxin 2 Subtypes, Stx2n as Well as Stx2j, Stx2m, and Stx2o, in the United States. Microorganisms. 2023 Oct 14;11(10) Available at: https://www.ncbi.nlm.nih.gov/pubmed/37894219
  2. European Food Safety Authority (EFSA) Panel on Biological Hazards (EFSA BIOHAZ Panel). Pathogenicity assessment of Shiga toxin-producing Escherichia coli (STEC) and the public health risk posed by contamination of food with STEC. EFSA Journal 2020;18(1):5967. Available at: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2020.5967
  3. European Centre for Disease Prevention and Control (ECDC). Surveillance Atlas of Infectious Diseases. Stockholm. Available at: http://atlas.ecdc.europa.eu/public/index.aspx?Dataset=27&HealthTopic=59
  4. Freedman SB, van de Kar N, Tarr PI. Shiga Toxin-Producing Escherichia coli and the Hemolytic-Uremic Syndrome. N Engl J Med. 2023 Oct 12;389(15):1402-14. Available at: https://www.ncbi.nlm.nih.gov/pubmed/37819955
  5. Menge C. The Role of Escherichia coli Shiga Toxins in STEC Colonization of Cattle. Toxins (Basel). 2020 Sep 21;12(9) Available at: https://www.ncbi.nlm.nih.gov/pubmed/32967277
  6. Pires SM, Majowicz S, Gill A, Devleesschauwer B. Global and regional source attribution of Shiga toxin-producing Escherichia coli infections using analysis of outbreak surveillance data. Epidemiol Infect. 2019 Jan;147:e236. Available at: https://www.ncbi.nlm.nih.gov/pubmed/31364563
  7. Isler M, Wissmann R, Morach M, Zurfluh K, Stephan R, Nuesch-Inderbinen M. Animal petting zoos as sources of Shiga toxin-producing Escherichia coli, Salmonella and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae. Zoonoses Public Health. 2021 Mar;68(2):79-87. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33382208
  8. Baker KS, Dallman TJ, Thomson NR, Jenkins C. An outbreak of a rare Shiga-toxin-producing Escherichia coli serotype (O117:H7) among men who have sex with men. Microb Genom. 2018 Jul;4(7) Available at: https://www.ncbi.nlm.nih.gov/pubmed/29781799
  9. Vusirikala A, Rowell S, Dabke G, Fox G, Bell J, Manuel R, et al. Shedding and exclusion from childcare in children with Shiga toxin-producing Escherichia coli, 2018-2022. Epidemiol Infect. 2024 Feb 26;152:e42. Available at: https://www.ncbi.nlm.nih.gov/pubmed/38403892
  10. Sayk F, Hauswaldt S, Knobloch JK, Rupp J, Nitschke M. 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. Front Public Health. 2024;12:1364664. Available at: https://www.ncbi.nlm.nih.gov/pubmed/38699424
  11. Parsons BD, Zelyas N, Berenger BM, Chui L. Detection, Characterization, and Typing of Shiga Toxin-Producing Escherichia coli. Front Microbiol. 2016;7:478. Available at: https://www.ncbi.nlm.nih.gov/pubmed/27148176
  12. Sim EM, Fong W, Suster C, Agius JE, Chandra S, Suliman B, et al. STECode: an automated virulence barcode generator to aid clinical and public health risk assessment of Shiga toxin-producing Escherichia coli. bioRxiv. 2024:05.07.593058. Available at: https://www.biorxiv.org/content/biorxiv/early/2024/05/08/2024.05.07.593058.full.pdf
  13. Freedman SB, Xie J, Neufeld MS, Hamilton WL, Hartling L, Tarr PI, et al. Shiga Toxin-Producing Escherichia coli Infection, Antibiotics, and Risk of Developing Hemolytic Uremic Syndrome: A Meta-analysis. Clin Infect Dis. 2016 May 15;62(10):1251-8. Available at: https://www.ncbi.nlm.nih.gov/pubmed/26917812
  14. Food and Agriculture Organization (FAO) of the United Nations World Health Organization (WHO). Shiga toxin-producing Escherichia coli (STEC) and food: attribution, characterization, and monitoring: FAO/WHO; 2018. Available at: https://iris.who.int/bitstream/handle/10665/272871/9789241514279-eng.pdf?sequence=1
  15. Hall JM, Falcon IZ, Elward AM, Daniels EA, Greene SE, Cabler SS, et al. Petting Zoos as an Unsuspected Source of Pediatric Infections. Pediatr Infect Dis J. 2023 Apr 1;42(4):346-9. Available at: https://www.ncbi.nlm.nih.gov/pubmed/36728537
  16. World Health Organization (WHO). Five keys to safer food manual: WHO; 2006. Available at: https://iris.who.int/bitstream/handle/10665/43546/9789241594639_eng.pdf?sequence=1
Page last updated 22 Aug 2024