A dangerous strain of salmonella is becoming more common in meat in the UK, unpublished government records show.
Test results obtained by the Bureau of Investigative Journalism (BIJ) and the Guardian reveal a rise in poultry products contaminated with salmonella infantis, with raw and processed meat found to be affected. Beef, pork and animal feed have also tested positive for the bacteria, which can cause serious illness that sometimes proves fatal.
Some of the tests also revealed antibiotic-resistant infections, meaning treatment options for anyone becoming seriously ill could be reduced. Such “superbug” variants, known as multidrug-resistant salmonella infantis, have been linked to major food poisoning outbreaks including one in the US in which at least one person died.
Although some of the contaminated meat originated from outside the UK, salmonella infantis has also been found on UK poultry farms, suggesting the strain may have taken hold in this country.
Salmonella bacteria are found in the guts of poultry and livestock. Birds and animals can be infected through feed, in hatcheries or through faeces on the way to abattoirs, where slaughter and processing can also spread the infection.
Salmonella poisoning can be life-threatening, particularly for infants and elderly people. Although most people will recover without the need for antibiotics, the drugs are often recommended in the most serious cases.
There are more than 2,000 types of salmonella, and salmonella infantis is regarded as being among the most virulent, frequently causing illness in humans and spreading rapidly on farms. The strain has become well established in parts of the EU poultry industry but has rarely been found on UK farms.
Numbers for this particular strain are still low. The most recent public health data available for the UK suggests about 400 people were infected with salmonella infantis in 2019 and 2020, although the true figure could be higher as not every case is reported.
But a report by the Animal and Plant Health Agency on salmonella infantis outbreaks on UK chicken farms said that “once introduced within a country, the speed at which infantis spreads and establishes itself within the production chain of that country gives rise to great concern”.
Responding to the investigation’s findings, Robin May, the chief scientific adviser of the Food Standards Agency, said: “The risk of people getting salmonella infections through handling and consuming contaminated meat, including breaded chicken products, is very low so long as good hygiene and cooking practices are followed.”
Richard Griffiths, the chief executive of the British Poultry Council, said: “The prevalence and type of salmonella in livestock changes over time and with varying environments, which is why the monitoring programmes are in place. The on-farm monitoring has clearly worked in these instances and the information from them can be used to develop control plans as required.”
Internal records released after freedom of information requests to Northern Ireland’s Department of Agriculture, Environment and Rural Affairs (Daera) revealed that tests on meat products and other commodities had detected salmonella infantis on at least 114 occasions since 2016. Northern Ireland is a powerhouse of chicken production, supplying 30% of the UK poultry market.
Raw poultry meat was the most commonly contaminated product, with a steep rise in detections recorded in 2020 and 2021. Some raw pork and beef meat was also found to be infected, as was grain used as livestock feed. UK government records show processed chicken products including goujons and kievs were also found to be contaminated in Northern Ireland.
Separate internal Daera records seen by the BIJ reveal that tests on some of the contaminated meat and feed found antibiotic-resistant strains of salmonella infantis. In 2020, nine poultry products and one pork item were recorded as harbouring multidrug-resistant salmonella infantis, along with one feed product.
Superbug variants of salmonella were also found during separate UK-wide tests conducted by the Food Standards Agency in 2021, including in two supermarket chicken goujon products.
In many of these cases, the contaminated products showed partial or full resistance to ciprofloxacin, a fluoroquinolone antibiotic that is often used to treat serious food poisoning. Fluoroquinolones were once widely used on UK chicken farms and are still used in poultry production internationally.
Cóilín Nunan, a scientific adviser to the Alliance to Save Our Antibiotics, said it was “particularly alarming that 70% of the isolates found have intermediate or full resistance to fluoroquinolone antibiotics”. He added: “Fluoroquinolones are highest-priority, critically important antibiotics which are key treatments for serious salmonella infections.”
The records do not show the origins of all the contaminated meat and feed samples, stating that they included the UK and other countries, but Ireland and Hungary were referred to.
The BIJ has learned that salmonella infantis, including superbug variants, was found on four occasions on poultry farms in Northern Ireland in 2019 and 2020, and has been found at least five times on chicken farms in England and Wales since 2013, including twice in Herefordshire in 2021. In one of the Herefordshire cases, the detection prompted the culling of more than 100,000 infected chickens.
In Northern Ireland, however, it appears no birds were destroyed, meaning infected products were free to be sold.
“When salmonella infantis was isolated, a public health advisory letter was issued to the flock keeper,” Daera documents state. “The flocks and any associated products were not placed under restriction. Advice was given on control and elimination of infection.”
Daera confirmed there had been an increase in salmonella infantis detected in 2020 and said it was “concerned about the increase in prevalence of S infantis across Europe over the last decade and particularly the levels of antimicrobial resistance it displays. Officials will continue to monitor this situation and take action as required.”
It said the majority of cases were connected to imported meat. Daera said the salmonella infantis cases found in poultry flocks in 2020 and 2019 “had a different AMR resistance profile to isolates originating from Europe and have not been associated with the large human outbreaks that have been reported in parts of Europe”.
Unlike several other strains of salmonella known to pose a potential public health risk, salmonella infantis in the UK is not regarded as a “regulated” strain in meat chickens, meaning there is no legal requirement for infected birds to be destroyed. Instead, records show, “attempts are made to manage [cases] in a similar manner to the regulated [strains] but on a voluntary basis”.
Nunan said salmonella infantis could cause serious infections in humans, “so these bacteria should not be allowed to spread uncontrolled in the food chain”.
The wide use of antibiotics in farming can create incubators for deadly drug-resistant diseases. The UK poultry industry has significantly cut its annual usage of antibiotics in the past decade after concerns about the spread of antibiotic-resistant bacteria. It is considered one of the world’s biggest public health threats; a UK government review estimated superbugs kill 700,000 people worldwide a year.