Enteric Escherichia Coli infections
The E. coli that cause enteric diseases are of different serotypes from those that cause diseases elsewhere. Five main types are recognised.
1. Enterotoxogenic E. coli (ETEC) produces a diarrhoeal illness.
Pathogenesis: Two toxins are produced, one that is heat stable and one that is heat labile. The toxins are coded for on plasmids and can therefore be transferred between bacteria. The heat labile toxin resembles cholera toxin and acts in a similar way. The heat stable toxin activates guanylate cyclase also resulting in secretory diarrhoea.
Clinically three syndromes occur with this infection: A cholera-like illness, traveller’s diarrhoea and childhood diarrhoea, which may vary in severity.
2. Enteroinvasive E. coli (EIEC) produces a very similar illness to bacilliary dysentery (shigellosis).
3.Enteropathogenic E. coli (EPEC) causes an infantile gastroenteritis.
Pathogenesis: Toxins are thought to be involved, the bacteria attaches to and damages intestinal epithelium.
Clinical: The condition causes a diarrhoeal illness primarily in children below 2 years.
4. Enterohaemorrhagic E. coli (EHIC) includes verotoxin producing E. coli 0157:H7.
Pathogenesis: The bacteria produce a shigellalike cytotoxin (Shiga toxin). Infections are associated with contaminated food, particularly hamburgers, only a small bacterial load is required to cause disease.
Clinical: Patients suffer from bloody diarrhoea and colitis. Haemolytic uraemic syndrome may complicate infections with EHIC.
5. Enteroaggregative E. coli (EAEC or EaggEC).
Pathogenesis: The bacteria produce a cytotoxin and stimulate IL-8 production. It is most common in the developing world but also found in the United Kingdom, especially in immunocompromised hosts.
Clinical: Traveller’s diarrhoea which lasts up to 4 days, or persistent diarrhoea in immunocompromised.
Patients require adequate rehydration, normally orally. Most infections are selflimiting. In severe cases, particularly if there are systemic symptoms, ciprofloxacin is used. It has been suggested from retrospective studies that treatment of E. coli 0157 with antibiotics may result in increased rates of haemolytic uraemic syndrome, but the treated patients were also more seriously unwell.