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.
AGES - Austrian Agency for Health and Food Safety
