Superbug found in milk ‘may be passing to people’

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.

The discovery has also 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: “This new evidence confirms our long-held view of the importance of absolutely minimising the use of antibiotics especially those closely related to antibiotics used by people. This requires excellent husbandry, and much reduced stress on our animals.

“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.

Mark Holmes and his team stumbled on the new MRSA bug while investigating mastitis, a serious and potentially lethal disease which affects dairy cows.

The research is published today (FRI)in the journal The Lancet Infectious Diseases.

MRSA is a drug-resistant form of a usually harmless common bacterium which can be deadly when it infects wounds.

The bug, often found in hospitals, was linked to 1,593 deaths in 2007 but since then the number of suspected fatal cases has fallen dramatically. There were 1,290 in 2008 and 781 in 2009.

Alarm bells rang over the new strain when it showed itself to be drug-resistant yet impossible to identify using standard tests, leading to the risk of people being prescribed the wrong antibiotics.

Using an upgraded test, scientists subsequently found MRSA bacteria with the same mutated gene in 13 of 940 samples from 450 dairy herds in England.

Further research confirmed that the strain was in the human population. Samples taken from screening tests and people treated for MRSA revealed 12 instances of the strain from Scotland, 15 from England and 24 from Denmark. Later the strain was also identified in Ireland and Germany.

The scientists also spotted a “clustering” of human and cow samples containing exactly the same sub-type of the new MRSA strain. This suggested transmission between cattle and humans.”

Colleague Laura Garcia-Alvarez said it was “certainly worrying” to find the same new strain in both cows and humans. But she pointed out that the pasteurisation of milk would keep the bacteria out of the food chain She said: “Workers on dairy farms may be at higher risk of carrying MRSA, but we do not yet know if this translates into a higher risk of infection. In the wider UK community, less than one per cent of individuals carry MRSA – typically in their noses – without becoming ill.”

Unpasteurised dairy products, including cheese, are not thought to be a serious concern.

Rob Newbery, chief dairy adviser at the National Farmers’ Union, said: “This report should not be cause for alarm to consumers, as it confirms the pasteurisation of milk completely destroys MRSA bacteria. It is important to remember that the health and welfare of cows are of paramount importance to the British dairy farmer.”

“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.”