A new strain of the MRSA “superbug” has been found in British cows and is believed to be infecting humans.
Environmental campaigners say the new strain has emerged because of the over-use of antibiotics by dairy farmers.
Dr Mark Holmes of Cambridge University, who led the research, said this was a “credible hypothesis”.
The researchers, writing in the Lancet Infectious Diseases Journal, say there is no additional health risk from eating milk and dairy products.
MRSA, or methicillin-resistant Staphylococcus aureus, is a drug-resistant form of a usually harmless bacterium which can be deadly when it infects wounds.
The 35 or so strains of antibiotic-resistant superbugs are genetically fairly similar. However, this new variety is very different and it is thought that it might have first emerged from cows.
Its discoverers have dubbed it “New MRSA”
Antibiotics are widely used by dairy farmers to treat cows with mastitis. However over-use means some bacteria become resistant and difficult to treat if humans become infected.
Dr Holmes said the problem might be exacerbated by financial pressures on diary farmers.
“If you drive your cows harder to produce more milk you get more mastitis,” he told reporters at a news conference.
MRSA
The Soil Association has called for a complete ban on routine use of antibiotics in farming.
Soil Association director Helen Browning said: “Dairy systems are becoming ever more antibiotic-dependent. We need to get farmers off this treadmill, even if that means that milk has to cost a few pennies more”.
National Farmers’ Union chief dairy adviser Rob Newberry said the health and welfare of cows were of “paramount importance” to British dairy farmers.
“In the interests of human and animal health, and animal welfare, it is important that veterinary medicines are administered as little as possible but as much as necessary,” he said.
“Any antibiotic or veterinary medicine being administered to a food producing animal has strict conditions of use, including milk and meat withdrawal times, and in general, under European law, would only be available under prescription.”
Dr Holmes and his colleague Dr Laura Garcia-Alvarez discovered the new strain while studying a bacterium known to cause mastitis in cows.
They found that, like other MRSA strains, it was resistant to the most commonly used antibiotics. However, the bug was found to be genetically very different.
Subsequent research showed that the strain was also present in humans.
Dr Garcia-Alvarez says that finding a new strain in both in humans and cows is “very worrying”.
“Workers on dairy farms are at higher risk of carrying MRSA but we don’t yet know if this translates to a higher risk [of them becoming ill],” she said.
Dr Holmes said very few people had been infected with the new strain, probably fewer than 100 a year in the UK. “But it does appear that the numbers are rising,” he says.
The Health Protection Agency said the risk of becoming infected with the new strain was “very low”.
Dr Holmes and Dr Garcia-Alvarez will now investigate the prevalence of the new strain and whether it is more or less harmful than current strains.
They also plan to conduct studies on farms to look for more MRSA strains of this type and explore any potential risks to farm workers.
MRSA is often found in hospitals and was linked to 1,593 deaths in 2007.
Since then the number of suspected fatal cases has fallen dramatically. There were 1,290 in 2008 and 781 in 2009.
A Department of Health spokesman said: “From the available evidence, we understand this new form of MRSA is rare in the UK and is not causing infections in humans.
“However, our expert committee, ARHAI, will be reviewing this issue at their next meeting and will consider potential medical, veterinary and food safety issues.”
A Food Standards Agency spokesman said the study did not provide direct evidence that humans were being infected with MRSA from cattle.
“The risk of contracting this new strain of MRSA through drinking milk is extremely low because the vast majority of cows’ milk is pasteurised and the pasteurisation process destroys all types of MRSA,” he added.
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Nurses are required to regularly wash their hands and disinfect bed frames and mattresses, but underestimate the risk of infection from dirty pillows, a report said.
But dead skin, dandruff, dirty air and contaminated fluids found on pillows in hospital wards expose patients to the risk of diseases ranging from seasonal flu to chickenpox, hepatitis and even leprosy, it was claimed.
The study by The Barts and The London NHS Trust found 30 different types of infection in a sample of pillows taken from hospital wards, posing a significant risk of infection.
While used linen and bedding is changed and laundered between patients and is routinely cleaned, the study found a “very high and unacceptable percentage” of damaged pillows on three test wards.
Tears to the lining or stitching of pillows mean they cannot be effectively cleaned and patients could be exposed to infection through the mouth, nose, eyes and ears, the report said.
Germs are released through tears and the stitching of standard NHS pillows when pressure is applied – for example when a patient lays their head down, it added.
The study was sponsored by SleepAngel, which has developed a hermetically sealed pillow to minimise the risk of spreading infection through stitching. Tests showed that after three months of use in hospitals, none of these pillows were contaminated on the inside.
Dr Arthur Tucker, Principal Clinical Scientist and Senior Lecturer at St. Barts and the London Hospitals and author of the report, said: “The presence of these bugs means that they can and will be passed to patients.”
A new strain of MRSA has been found in cows’ milk.
The same strain of the superbug has also been discovered in patients being treated for wound infections.
It is the first time any form of MRSA has been traced to dairy cattle in the UK.
However, experts insist there is no overall threat to the safety of milk sold in shops.
This is because any kind of MRSA in dairy products is destroyed by the heat used in the process of pasteurisation.
Scientists warned that further research would be required to find out if humans were spreading the bug to cows or vice versa.
The discovery raises concern that intensive farming methods may be encouraging the emergence of new MRSA strains which are resistant to an ever-wider range of antibiotics.
Organic farming lobby The Soil Association last night called for a complete ban on routine use of antibiotics in livestock because of fears they may promote drug-resistant bacteria.
Helen Browning of the Soil Association, said: ‘Under acute price pressure, dairy systems are becoming ever more antibiotic dependent.
We need to get farmers off this treadmill, even if that means that milk has to cost a few pennies more.
‘That would be a very small price to pay for maintaining the efficacy of these life-saving drugs.’
The MRSA strain was discovered by researchers at Cambridge University investigating mastitis, a serious disease in dairy cows.
Dr Mark Holmes, a veterinary scientist who led the research, said they found a drug resistant form of MRSA which did not match existing strains.
MRSA, or methicillin-resistant Staphylococcus aureus, is a usually harmless and common bacterium carried on the skin which can be deadly if it infects wounds.
Checks found the mutated MRSA in 13 of 940 samples from 450 English dairy herds.
Further research confirmed the strain was also in humans, says a report published today in the journal The Lancet Infectious Diseases.
Samples from screening tests and patients treated for MRSA wound infections revealed 12 instances of the strain from Scotland, 15 from England and 24 from Denmark. It was also identified in Ireland and Germany.
The scientists also spotted a ‘clustering’ of human and cow samples that suggested transmission between them.
Dr Holmes said: ‘Although there is circumstantial evidence that dairy cows are providing a reservoir of infection, it is still not known for certain if cows are infecting people, or people are infecting cows.’
MRSA infection is often found in hospital patients, but a drive to improve hygiene has dramatically cut the number of fatal cases.
There were 1,290 in 2008 and 781 in 2009.
Researchers have no information about the virulence of the new strain, which has so far not been linked to any deaths.
It is treated with the same antibiotics used against ‘normal’ MRSA.
They said workers on dairy farms might be at higher risk of becoming carriers, but the food chain was unlikely to be affected.
Unpasteurised milk can only be sold directly from farms in England, and bugs in unpasteurised cheeses struggle to survive the human digestive system. The Department of Health said it would review the issue.
A spokesman from the Food Standards Agency said: ‘The risk of contracting this strain of MRSA through milk is extremely low because the vast majority of cows’ milk is pasteurised.’
A new strain of the MRSA “superbug” has been found in the milk of British cows as well as swab samples taken from humans.
Experts have ruled out any general threat to the safety of milk or dairy products, but they point to “circumstantial” evidence of the bacteria passing between cattle and the human population.
However, the findings, published in the journal The Lancet Infectious Diseases, have fuelled controversy over intensive farming methods and the way antibiotics are used to protect livestock.
The Soil Association called for a complete ban on routine use of the drugs, which is said to promote the development of drug-resistant bacteria. It also urged an end to the continuing economic pressure on farmers to cut costs and maintain low prices.
Helen Browning, director of the Soil Association, said: “In the relentless drive for increased per animal productivity, and under acute price pressure, dairy systems are becoming ever more antibiotic dependent. We need to get farmers off this treadmill, even if that means that milk has to cost a few pennies more. That would be a very small price to pay for maintaining the efficacy of these life-saving drugs.”
The Cambridge University veterinary scientist who led the research spoke of the “tremendous financial pressure” placed on farmers by the purchasing power of big supermarkets. Dr Mark Holmes and his team stumbled on the new MRSA bug while investigating mastitis, a disease which affects dairy cows.
MRSA, or methicillin-resistant Staphylococcus aureus, is a drug-resistant form of a usually harmless common bacterium which can be deadly when it infects wounds.
Alarm bells rang over the new strain when it showed itself to be drug-resistant yet impossible to identify using standard molecular tests. The strain turned out to have a key gene for antibiotic resistance, called mecA, which was different from the one for “normal” MRSA.
A Department of Health spokesman said: “From the available evidence, we understand this new form of MRSA is rare in the UK and is not causing infections in humans. However our expert committee (Advisory Committee on Antimicrobial Resistance and Healthcare Associated Infections) will be reviewing this issue at their next meeting and will consider potential medical, veterinary and food safety issues.”
A spokesman from the Food Standards Agency said: “The data from this study does not provide direct evidence that humans are being infected with MRSA from cattle. The risk of contracting this new strain of MRSA through drinking milk is extremely low because the vast majority of cows’ milk is pasteurised and the pasteurisation process destroys all types of MRSA. Additionally most of the samples of the new strain of MRSA found were in milk from cows with udder infections. Milk from these cows is banned for human consumption.”