UK safety authorities have highlighted a trebling in the number of salmonella cases reported this year- with eggs imported from Spain investigated as one possible source for almost a third of incidences.

The Food Standards Agency (FSA) and the Health Protection Agency (HPA) confirmed a total of 443 cases of Salmonella Enteritidis phage type (PT) 14b have been reported since the start of the year, compared to 137 occurrences in the whole of 2008. Investigations are also underway into a possible link with two deaths.

The agencies have launched a probe into 14 infection clusters since August - involving 144 cases - to find out if there is a common source for the illnesses. All the clusters have been associated with a number of catering establishments and one care home. During the care home outbreak, two elderly people died. Inquests have been ordered to find the cause of death after post-mortem results were "inconclusive".

Imported eggs?

The agencies are examining a theory the clusters may be linked to eggs imported into the UK but stressed there was no conclusive evidence yet to support this.

"Investigations are ongoing into a possible link to eggs sourced from an approved establishment in Spain, and the UK and Spanish authorities are working in close cooperation to investigate this", said a FSA statement.

The HPA added: "From investigations of supply chains, eggs collected from catering premises in five of the outbreaks (three oriental restaurants, two cafes) were produced from the same approved establishment in Spain."

This was confirmed by the distinguishing egg stamp mark on shell eggs, said the body. Two subsequent samplings of eggs supplied by this producer from a UK distributor found infected eggs in two out of 80 and 1 out of 20 tests respectively.

EU regulations

Since January 2009, all EU states have been obliged to introduce a Salmonella National Control Programme and carry out testing for salmonella in laying flocks. The aim of the initiative is to reduce the incidence of salmonella in laying flocks and the egg market but regulators recognise it cannot stamp out infections completely.

Under the regulations, eggs from flocks testing positive for salmonella - specifically S. Enteritidis or S. Typhimurium - cannot be sold directly to consumers and are instead sent for pasteurisation.

Salmonella is one of the most common causes of food poisoning in the UK and is sometimes found in unpasteurised milk, raw meat and poultry, as well as eggs and products containing raw egg. The majority of eggs on sale in shops in the UK are of UK origin, and recent surveys have shown there is a very low incidence of salmonella in UK eggs.

The FSA cautioned that it was impossible to guarantee that any egg will be free of salmonella and stressed the importance of safe storage, preparation and cooking of the products.