Escherichia coli including Verotoxin-producing E. coli (VTEC)

Escherichia coli

Changed on: 08.09.2021
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Bacteria of the species Escherichia (E.) coli with the ability to produce the toxin verotoxin are called verotoxin-producing E. coli (VTEC). Based on their different antigen structures, they can be classified into different serotypes (currently about 180 different O-serotypes). VTEC O157:H7 is considered to be the prototypical strain. In addition, serotypes O26, O103, O111, O145, O146, O121, O128, O91, O104 and O113 are common as causative agents of human diseases. The bacteria are heat-sensitive, but survive in frozen food and in acidic conditions. The terms shigatoxin-producing E. coli (STEC) and enterohaemorrhagic E. coli (EHEC) are used as synonyms for VTEC.

Occurrence

Since 1982, VTEC has been known to cause diarrhoea and kidney failure due to hemolytic-uremic syndrome.

Reservoir

ruminants (cattle, sheep, goats) and wild animals (roe deer and stags)

Mode of transmission

The bacteria are mainly transmitted through consumption of contaminated food, such as raw minced beef, sausages, salami, raw milk, but also plant foods cultivated on fields fertilized with cattle manure and consumed raw, as well as industrially produced sprouts. Another transmission route is direct contact with ruminants (petting zoos), if no appropriate hygiene measures (washing hands with soap) are carried out afterwards. Human-to-human transmission must be taken into account especially in community facilities (kindergardens, homes for the elderly, etc.). 50-100 CFUs of VTEC may already be sufficient to trigger the disease in healthy people.

Incubation period

Between 2 and 8 days, usually 3-4 days.

Symptoms

Disease symptoms usually start with watery diarrhoea, which often becomes bloody after a few days and can be accompanied by severe nausea, vomiting and abdominal pain. The disease is predominantly self-limiting and lasts eight to ten days on average. In about 5-10% of patients, especially in small children, a characteristic secondary disease, the life-threatening hemolytic uremic syndrome (HUS), can occur days after the onset of diarrhoea. The toxin binds to special receptors on the cell walls and damages blood capillaries; this can lead to kidney failure (lack of urine production), anaemia, reduced platelet count, skin bleeding and neurological changes.

Treatment

Treatment with antibiotics is generally considered to be contraindicated, as the bacteria produce more toxin when exposed to antibiotics, which can increase the complication rate. Rebalancing water and electrolyte balance is usually sufficient. In severe cases (e.g. HUS), intensive medical treatment, like blood purification therapy, is required.

Preventive measures

Since ruminants and wild ruminants are regarded as the reservoir of VTEC, strict compliance with hygiene regulations, e.g. washing hands after contact with animals, is of great importance. Persons suffering from VTEC infections must not be employed in the commercial production, treatment or market placing of food until the public health authority decides that there is no longer any risk of further spreading the disease. This also applies to employees in kitchens of restaurants, canteens, hospitals, infant and children's homes and in communal catering.

Situation in Austria

Human

In 2020, 304 laboratory-confirmed VTEC cases were reported (EMS, as of 12/01/2021). The incidence was 3.4/100,000 population. The increase in cases since 2016 is primarily due to the increased use of culture-independent detection methods in laboratories, which means that more patient samples are also being tested for these pathogens. The severe complication HUS occurred in 11 patients; this number of cases corresponds to the long-term average.

Figure 1: VTEC cases in Austria

Figure 2: Incidence of VTEC diseases and proportion of HUS cases

Food

In 2020, 1,203 food samples were tested for VTEC, of which 977 samples were of animal origin.

Meat samples: VTEC was found in 7 out of 120 raw meat samples, with this pathogen detected mainly in meat samples from wild ruminants (6 out of 47 samples). VTEC was not detected in any fresh beef sample (n = 44) (2018: 4 positives in 68 samples).VTEC was identified four times in raw milk (3 times cow's milk, 1 time sheep's milk), all other dairy products were VTEC negative.Typing of VTEC isolates revealed different serotypes (each serotype once or twice). Only VTEC O146:H28 (eae negative, vtx1 negative, vtx2 positive) showed a low cluster with 5 isolates in 2020.

Food category N tests n positive % positive
other foods/meals 49 0 0
fermented sausages 167 2 0.01
Meat and meat preparations, fresh 197 2 0.01
Meat preparations and products, raw or ready-to-eat 12 0 0
Meat preparations and products, ready to eat 175 0 0
Fresh cheese made from pasteurized or raw milk 116 0 0
Fruits, fresh or frozen, whole or sliced 90 0 0
Vegetables, mushrooms, herbs, spices 121 0 0
Cereals 32 1 0.03
Cheese, unspecified 17 0 0
Cow's milk, raw, for consumption 74 3 0.04
Milk, raw 8 1 0.12
Dairy products 46 0 0
Soft cheese made from pasteurized or raw milk 34 0 0
Game, fresh 50 7 0.14
Wild boar, fresh 15 0 0

Professional information

Human Medicine

Diagnostics

After clinical suspicion, VTEC is diagnosed by detection of a verotoxin gene or the cultural cultivation of the germs, by detection of verotoxin in stool or (only in HUS) by detection of specific antibodies in blood.

National Reference Centre for Escherichia coli - VTEC - EHEC

  • Detection of EIEC, EPEC, ETEC, EAggEC and VTEC in human stool samples
  • Isolation and culture of VTEC from human stool, food and environmental samples using selective culture media, immunomagnetic separation, slide agglutination and PCR
  • Confirmation and type identification of submitted isolates by biochemical and molecular biological methods
  • Serotyping
  • Detailed type identification of VTEC: typing of shigatoxin genes (PCR), subtyping of shigatoxin genes and typing of further virulence genes (whole genome sequencing)
  • Identification of epidemiological correlations using whole genome sequencing data
  • Detection of specific antibodies against HUS in human serum
  • Maintaining a culture collection of all human, veterinary, feed and food isolates
  • Clarification of infection sources and modes of transmission in investigations of outbreaks
  • Advice on questions on diagnostics, reporting requirements, epidemiology, food safety, prevention or preventive measures
    Nationale Referenzzentrale für Escherichia coli einschließlich Verotoxin-bildender E. coli - Jahresbericht 2019 (1.14 M)
    download file

Contact, forms

National Reference Centre for Escherichia coli - VTEC - EHEC

Beethovenstraße 6
8010 Graz

Mag. Dr. Sabine Schlager
Tel.: +43 50 555-61211
E-mail: sabine.schlager@ages.at

Downloads

    Folder Verotoxin bildende Escherichia Coli (VTEC) (282 K)
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    Nationale Referenzzentrale für Escherichia coli einschließlich Verotoxin-bildender E. coli - Jahresbericht 2018 (2.41 M)
    download file  | open PDF

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