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MICROBIOLOGISTS DISCOVER HOW FOOD POISONING E. COLI O157 BECAME SO TOXIC
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. Scientists are now beginning to understand this phenomenon, according to research presented at the Society for General Microbiology's 156th Meeting at Heriot-Watt University, Edinburgh. Normally E. coli bacteria live in the intestine and don't cause us any problems, 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. "Sometime before 1982 an unknown virus that attacks bacteria passed on a bit of genetic coding to E. coli and this allowed 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," says Dr Heather Allison from the University of Liverpool. The Liverpool researchers have 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. The particular virus identified by Dr Allison and colleagues uses this newly identified receptor to spread to fresh hosts. In addition, this research has discovered that the toxin-encoding virus can infect a single cell multiple times, which can potentially improve the bacterium's ability to cause serious disease and the virus's ability to spread to other bacteria. This will have implications for everyone involved in food production, from farmers to supermarkets and food hygiene experts.
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