enterohaemorrhagic E. coli

Last edited 03/2020 and last reviewed 01/2021

Enterohaemorrhagic E. coli cause a haemorrhagic colitis, haemolytic uraemic syndrome and thrombotic thrombocytopaenic purpura by the production of verotoxins.

Enterohaemorrhagic serotypes include O157.H7.

• Enterohemorrhagic Escherichia coli) (STEC, EHEC)
• the enterohaemorrhagic E. coli (EHEC) are now generally referred to as Shiga toxinproducing E. coli (STEC). They are capable of producing the toxins Shiga toxin 1 (stx1) and Shiga toxin 2 (stx2) (named due to their similarity to the toxin produced by Shigella dysenteriae type 1).
• STEC replaces the previous terminology ‘verocytotoxin-producing E. coli (VTEC)’.
• Shiga toxin can be produced by both O157 and non-O157 serotypes. All O157 types (stx +ve and –ve) and non-O157 STEC (i.e. stx +ve) infections require urgent Public Health action

They colonise the large intestine where they cause diffuse mucosal haemorrhages.

Approximately, 10-15% of people infected with STEC go onto develop HUS.

Children under 15 years old and older adults over the age of 65 years4 are more likely than other age groups to develop STEC-related HUS, particularly children under 5 years. In
England between 2009 and 2012, three quarters of HUS cases occurred in children (0-14 years)

Treatment is mainly supportive.

Summary:

Reservoir:

• Gastrointestinal tract of ruminants (in the UK mainly cattle, sheep and goats). Other animals and birds acts as transmission vectors

Transmission:

• Faecal-oral route
• ingestion of contaminated food (particularly undercooked meat, minced beef, salad products including water cress) water or unpasteurized milk
• person-to-person spread
• direct/indirect contact with an infected animal or their faeces
• environmental exposure e.g. swimming/playing in contaminated water, streams or ponds
• Seasonal outbreaks have been associated with farm visits to feed and handle calves and lambs

Incubation period:

• Usually 2-4 days for STEC O157 and similar for most strains of non-O157 STEC

Infectivity:

• shedding of organisms depending on strain of STEC and age of patient may be prolonged. It tends to be shorter in adults but there have been reports of children shedding for over 6 weeks

Reference:

• PHE (2019). Recommendations for the Public Health Management of Gastrointestinal Infections