Taxonomy
Family: Enterobacteriaceae, genus: Escherichia coli, E. coli O157.H7
E. albertii, E. fergusonii, E. hermannii, E. vulneris

Origin
E. coli O157:H7 is so-named because it expresses the 157th somatic (O) antigen identified and the 7th flagellar (H) antigen.

Natural habitats
E. coli O157 is found regularly in the faeces of healthy cattle, and is transmitted to humans through contaminated food, water, and direct contact with infected people or animals.

Transmission
E. coli O157 is transmitted by food and water, directly from one person to another, and occasionally through occupational exposure.
Most foodbourne outbreaks have been traced to foods derived from cattle, especially ground beef an raw milk.

Clinical significance
Human infection is associated with a wide range of clinical illness, including asymtomatic shedding, non-bloody diarroea, haemorrhagic colitis, haemolytic uraemic syndrome, and death.