Scientists find food bug source

There are over 2,500 types of Salmonella

A surge in cases of relatively rare form of Salmonella may be due to Spanish eggs not being cooked properly by caterers, experts suggest.

Cases of Salmonella Enteritidis PT14 rose sharply from under 200 a year before 2001 to 922 in 2003.

A Health Protection Agency report found people affected tended to have eaten eggs outside their home.

HPA tests showed eggs imported from Spain were probably the cause, though it said further checks were needed.

People who had been ill were more likely to have consumed eggs outside the home. Dr Sarah O'Brien, Health Protection Agency

The HPA began an investigation into the source of the food poisoning cases after seeing the increasing incidence of this type of Salmonella.

They interviewed 55 people who had been ill, and asked them about foods they had eaten and the kind of places they had eaten.

They then spoke to 102 randomly selected people so they could eliminate foods and places in order to discover what had caused the illness.

Genetic fingerprinting

Dr Sarah O'Brien, who is leading the investigation for the Agency said, "The results showed us that the people who had been ill were more likely to have consumed eggs outside the home.

"These eggs were consumed in a wide variety of shops and catering premises."

She added: "Our investigations in 2002 showed us that some outbreaks were caused by Spanish eggs.

"Using genetic fingerprinting, we have compared some of the human samples in 2003, with those taken from both humans and eggs in 2002 and they are all identical.

"This means the continued increase in infections caused by S. Enteritidis PT14b in 2003 might also have been be caused by eggs imported from Spain, but it is still too early for a definitive answer at this stage."

Dr O'Brien concluded, "Caterers need to remember that raw shell egg can be contaminated with Salmonella and follow Food Standards Agency advice that shell eggs should be cooked until the yolk is hard, and any products containing raw or lightly cooked eggs should be made using pasteurised eggs"

Preparation advice

Salmonella lives in the guts of animals and sometimes humans, and is usually spread by undercooked food or cross-contamination from raw foods.

It is usually unpleasant, rather than dangerous, and tends to cause diarrhoea, vomiting and a fever.

Cooking food thoroughly and making sure juices run clear when cooking meat should reduce the risk of spreading salmonella.

In addition, raw and cooked foods should be stored separately, and people should use different utensils and wash their hands after handling raw food.