How E.Coli became deadly to humans

A University of Liverpool scientist has discovered how the food poisoning bug E.Coli 0157 became deadly to humans.

Twenty-three years ago a harmless gut bacterium called E. coli developed the ability to kill people through food poisoning, bloody diarrhoea and kidney failure. Normally E. coli bacteria live in the intestine and don’t pose any danger, but some varieties can cause fatal food poisoning. The most serious in the UK is E. coli O157, which is carried by livestock (mainly cattle), and can enter the human food chain through contaminated meat and inadequate food processing.

Dr Heather Allison, from the University’s School of Biological Sciences, explains: "Sometime before 1982 an unknown virus that attacks bacteria passed on a part of genetic coding to E. coli that allows some strains to make Shiga toxin. This lethal poison causes the notorious food-borne infection that results in bloody diarrhoea and sometimes kidney failure in people.”

The team has now discovered how the virus can infect E. coli, by recognising a newly identified but common receptor on the surface of E. coli cells, which allows the viruses to gain entry into the bacteria. Once inside, the virus gives new genetic material to the bacterium, providing it with the ability to produce Shiga toxin.

In order to reduce the likelihood of picking up the E. Coli bug, Dr Allison suggests avoiding undercooked minced beef; foodstuffs in general that have come into contact with livestock faeces and have not been cooked or properly washed; untreated water contaminated with livestock faeces; and cooked foodstuffs that have come into contact with contaminated, uncooked meat products.