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

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.

In 2019, 286 laboratory-confirmed VTEC cases were reported. The incidence was 3.23/100,000 population. The severe complication HUS occurred in 16 patients.

In 2018, 1,174 food samples were tested for VTEC, 758 of which were meat samples: VTEC was found in 17 out of 313 raw meat samples (5.4%), with the pathogens mainly found in meat samples from wild ruminants (11 out of 49 samples). VTEC was found less frequently in meat samples from animals kept in stables (6 out of 255 samples). One of the 208 (0.5%) ready-to-eat meat products tested was found to be contaminated with VTEC. Two of the 237 (0.8%) sausages tested positive for VTEC: one in 57 tested raw sausages from game and one in 180 fermented sausages from mixed meat or where the animal species was not specified.

In all other samples (185 cheeses, 129 of which were made from raw milk, 69 milk products, 24 raw milk, 124 samples of fruit, fruits, vegetables and juices thereof and 14 other food preparations, no VTEC was detectable.

The type identification of the 20 VTEC isolates revealed 11 different serotypes, two of which (VTEC O146 and VTEC O91) are among those that cause more common diseases in humans in the EU. VTEC O146 was isolated from three samples of fresh game meat and one sample of fermented sausage without any specification of the animal species, VTEC O91 was isolated from three fresh meat samples, one each of beef, game and one without any specification of the animal species. Non-typable VTEC (VTEC Orough) was found in five samples of game meat, in four samples of fresh meat and in one raw sausage.

In accordance with EU requirements for monitoring and reporting antimicrobial resistance in zoonotic and commensal bacteria, 349 samples of beef and 350 samples of pork from all over Austria were tested for E. coli that produces ESBL, AmpC, or carbapenemase, in 2019. ESBL, AmpC, and carbapenemase are enzymes that act on various antibiotics (e.g. penicillin) and can render them ineffective.

• ESBL/ AmpC-forming E. coli were detected in seven samples of beef and 35 samples of pork
• Carbapenemase-forming E. coli were not detected in any sample

Focus action: Antibiotic-resistant germs in beef and pork - monitoring

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

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