Shiga toxin-producing Escherichia coli infection

Causative agent

Escherichia coli (E. coli) is a bacterium that is commonly found in the gut of humans and warm-blooded animals. Most strains of E. coli are harmless. Some strains, however, such as Shiga toxin-producing E. coli (STEC), can produce powerful toxins and cause severe foodborne disease. Among the subtypes, E.coli O157:H7 is the most important STEC serotype in relation to public health. Other serotypes e.g. E. coli O104:H4 can also cause serious disease and outbreaks.

Clinical features

Symptoms of STEC infection include abdominal cramps and diarrhoea that may in some cases progress to bloody diarrhoea. Fever and vomiting may also occur. In a small proportion of patients, the infection may lead to a life-threatening complication, for example haemolytic uraemic syndrome (HUS) resulting in kidney failure in young children. People of any age can become infected. Very young children and the elderly are more likely to develop severe illness, but even healthy older children and adults can become seriously ill.

Mode of transmission

STEC is transmitted to humans primarily through consumption of contaminated food, such as raw or undercooked ground meat products, contaminated fruits and vegetables and unpasteurised dairy products. Direct person-to-person transmission through the faecal-oral route can also occur. Waterborne transmission has been reported, both from contaminated drinking water and from recreational waters. Direct contact with farm animals or their environment is also an important risk factor for STEC infection.

Incubation period

It can range from 3 – 8 days, usually 3 – 4 days.

Management

Treatment for STEC infection is usually supportive. Fluid and electrolyte replacement is important when there is severe diarrhoea. Antibiotics are not recommended, and are likely to increase the risk of HUS. Patients with HUS may require specific supportive treatment and blood transfusion.

Prevention

Preventive measures for STEC infection are similar to those recommended for other foodborne diseases. Members of the public are advised to observe good personal and food hygiene:

• Adopt the 5 Keys to Food Safety in handling food, i.e. Choose (Choose safe raw materials); Clean (keep hands and utensils Clean); Separate (Separate raw and cooked food); Cook (Cook thoroughly); and Safe Temperature (keep food at Safe Temperature) to prevent foodborne diseases.
• Wash hands thoroughly with liquid soap and water before food preparation and consumption, after handling raw meat, after using the toilet or changing diapers, and after contact with animals.
• Cook food and boil water thoroughly before consumption. When cooking or reheating, the core temperature of the food should reach at least 70℃ for 30 seconds.
• Avoid consumption of unpasteurised milk or undercooked food.
• Consult your doctor immediately if you have gastrointestinal symptoms suspicious of STEC infection, particularly bloody diarrhoea.