Changing eating habits are responsible for an increase in stomach bugs, say scientists.

They have identified the gene make-up of a new bacterium which is responsible for three times as many cases of diarrhoea as salmonella.

Scientists believe that more people dining out and eating pre-prepared meals are responsible for a rise in cases.

Now the team of scientists in the UK and the Netherlands believe they could be able to develop better ways of identifying and controlling the bacterium.

The number of cases of diarrhoea caused by infection from the bacterium Campylobacter jejuni (C. jejuni) rose in England and Wales by 17% from 1997 and 1998.

Food poisoning

There are 60,000 cases of food poisoning caused by the bacterium in the UK annually. C. jejuni is often found in contaminated meat products, especially chicken.

The scientists, working under the Wellcome Trust's Sanger Centre, found that the bacterium's genome sequence is unusual. Several regions of its DNA sequence are hypervariable, meaning that they can change very rapidly.

This high level of variation, mostly in genes involved in making and modifying C. jejuni's surface structures, could be important in the bacterium's survival in the intestine and on food.

C. jejuni is also strongly associated with a form of neuromuscular paralysis known as Guillain Barre syndrome.

Dr Julian Ketley, of the University of Leicester's genetic department, said: "Despite its importance, effective disease prevention and control of Campylobacter in the food chain are hindered by a poor understanding of the biology of this organism and how it causes disease."

Human infection

Human infection is usually acquired by eating improperly cooked meat or contamination of uncooked food. Another source is via contaminated milk or water.

The bacteria colonise the intestines of a wide range of animals, but in non-immune people, infection frequently results in very unpleasant dysentery-like diarrhoea.

Dr Ketley said the team's findings would have implications for preventing illness.

"We will be able to design more specific hygiene systems in food production facilities. In addition, we will be able to devise better detection procedures so we can find this bacterium more easily."

Professor Brendan Wren at the London School of Hygiene and Tropical Medicine, who also took part in the research, said: "This is the first food-borne pathogen to be completely sequenced. Armed with this new wealth of information, scientists hope to devise intervention strategies to eliminate the organism from the food chain."

And Dr Steve Leach at the Centre for Applied Microbiology & Research in Salisbury said: "The genome sequence is going to be a huge step forward in understanding the origins and how it causes disease."