Escherichia coli is a complex group of gut bacteria that are found in all warm-blooded animals and are for the most part harmless. A few, however, cause disease in man and animals. The E. coli bacteria that produce a poison called Shiga toxin can produce a range of effects in man. One common effect is bloody diarrhoea followed by complications such as kidney failure (haemolytic uraemic syndrome). The bacteria may be spread through contaminated food or water, or from contact with animals.

A sequence of favourable circumstances needs to exist before E. coli can produce disease. The most important of these is the ability to produce Shiga toxin. The gene that codes for Shiga toxin is not innate, but is contained within bacteriophages. In other words, the bacterium needs first to be infected by a bacteriophage coding for Shiga toxin in order to produce the toxin itself.

In her work, Camilla Sekse studied E. coli O103:H25 bacteria isolated both from foodstuffs and patients from the E. coli outbreak of 2006. She and her colleagues discovered special features of these E. coli bacteria that separate them from ordinary, benign forms. This discovery lead to it being easier to demonstrate E. coli O103:H25 in suspect food products.