December 28, 2012
New strain MRSA detected in British milk supply
A new strain MRSA (Methicillin-resistant Staphylococcus aureus) in the British milk supply was identified by scientists from Cambridge University which is likely due to an overuse of antibiotics in the dairy industry.
The new strain, MRSA ST398, was found in seven out of 1,500 samples of bulk tank milk taken from five different dairy farms.
"This is definitely a worsening situation," Mark Holmes, of the department of veterinary medicine at Cambridge, told the local media. "In 2011 when we first found MRSA in farm animals, the Department of Environment, Food and Rural Affairs [Defra] initially did not believe it. They said we do not have MRSA in the dairy industry in this country."
"Now we definitely have MRSA in livestock. What is curious is that it has turned up in dairy cows when in other countries on the Continent it is principally in pigs."
The study was done between January and July 2012, and its findings were published in the scientific journal Eurosurveillance on December 13. While consumers should not have concerns about catching the meticillin-resistant Staphylococcus aureus if their milk is pasteurised, veterinarians and farm and slaughterhouse workers who come in contact with livestock are at greater risk.
Holmes said pressure from supermarket chains to keep down prices has forced the dairy industry to overuse antibiotics so cows do not get udder infections, which slow down milk production.
"Three classes of antibiotics rated as 'critically important to human medicine' by the World Health Organisation - cephalosporins, fluoroquinolones and macrolides - have increased in use in the animal population by eightfold in the last decade," the paper reports. Their overuse increases the probability that MRSA will evolve in the dairy population.
The cramped living conditions of cows and other livestock contributes to a more rapid spread of the bacteria. Holmes recommends increased regulation on how much antibiotics British vets can prescribe. Dairy supplies in Denmark and Norway are not at risk for developing MRSA because of stricter government controls in those countries.
