A strain of Salmonella resistant to the most powerful antibiotics has been found in the UK, France and Denmark.
The outbreak emerged in Africa then spread to Europe, picking up antibiotic resistance along the way, says a team of international researchers.
They are calling on health officials to step up monitoring to stop the “superbug” spreading globally.
Cases have grown from a handful in 2002 to 500 worldwide in 2008, they report in The Journal of Infectious Diseases.
Co-researcher Dr Simon Le Hello of Institut Pasteur in Paris, France, said: “We hope that this publication might stir awareness among national and international health, food, and agricultural authorities so that they take the necessary measures to control and stop the dissemination of this strain before it spreads globally, as did another multidrug-resistant strain of Salmonella, Typhimurium DT104, starting in the 1990s.”
Most of the millions of Salmonella infections a year are not serious, causing only mild stomach upsets. Occasionally, however, particularly in the elderly or in people with weakened immune systems, they can be life-threatening and may need treatment with antibiotics.
Salmonella
The strain, known as S. Kentucky, has developed resistance to the antibiotic Ciprofloxacin, often used for treating severe Salmonella cases.
French researchers started monitoring the strain after noticing a handful of cases in travellers returning from Egypt, Kenya and Tanzania.
Data from other countries suggests S. Kentucky arose in poultry in Egypt in the 1990s, and then spread to farm animals in various parts of Africa and the Middle East.
Although the first infections outside Africa seem to be in international travellers, more recent cases seem to have been acquired in Europe, perhaps through contaminated food, say the researchers. Cases have been seen in England, Wales, Denmark and France.
A spokesperson from the UK’s Food Standard’s Agency (FSA) said human Salmonella infections are rarely treated with antibiotics, and cooking food thoroughly will destroy any bacteria irrespective of whether the organism is resistant to antibiotics or not.
He added: “As part of the FSA strategy to reduce foodborne illness we recommend people follow some basic food safety rules: wash hands properly and keep them clean, cook food thoroughly, chill foods properly and avoid cross-contamination.
“These principles, which are designed to reduce the risk from pathogens, such as Salmonella, are equally applicable whether these pathogens are resistant to antimicrobials or not.”
A super-salmonella bug that cannot be treated by any drug is on the rise in Britain, scientists warn.
They think the strain originated in Egypt and is now being spread across Europe by contaminated fruit, vegetables and spices.
So far at least 200 Britons have been infected with the bug known as Salmonella Kentucky since 2000.
The scientists from the World Health Organisation warn that there have probably been many more cases which were never reported to health officials.
Figures show that the number of Britons infected with this particular type has trebled over the past decade.
In 2000 fewer than 20 cases were reported to the Health Protection Agency but this had gone up to 60 in 2008, the most recently available figures. It is not known if anyone has died from this strain.
There are around 2,500 different types of salmonella bacteria across the world lurking in soil or in the intestines of animals.
Most people catch the bug by eating infected chicken or eggs but it can also be spread by fruit or vegetables that have been contaminated in the soil.
It isn’t normally serious and symptoms include vomiting, diarrhoea, headaches and fever which clear up without treatment within a few days.
But it can be deadly in the elderly, young children and patients with long-term illnesses such as cancer and often they need antibiotics.
Scientists from the Institut Pasteur at the World Health Organisation in Paris say that this particular type is resistant to all types of drugs.
They are concerned it could spread very quickly around the world – and could prove deadly for the most vulnerable.
The scientists, whose study is published in the Journal of Infectious Disease, looked at the number of reported cases in England and Wales, France, Denmark and the U.S. between 2002 and 2008.
They discovered that in all countries the number of cases had increased substantially.
The scientists think that the strain originated in Egypt in the 1990s and has since spread to other African countries such as Morocco and Ethiopia through infected poultry.
They think it is now being spread across Europe through contaminated spices, fruit or vegetables imported from Africa.
Dr Le Hello, lead researcher, said: ‘We hope that this publication might stir awareness among national and international health, food, and agricultural authorities so that they take the necessary measures to control and stop the dissemination of this strain before it spreads globally.’