Two studies appear this week (one in The Lancet, the other in Antimicrobial Agents and Chemotherapy ) each independently identifying what are very closely related new strains of MRSA (Methicillin-resistant Staphylococcus aureus) that has been detected both in cows and in humans.

WASHINGTON, DC -- June 2, 2011 -- A distinctly new type of methicillin resistant Staphylococcus aureus (MRSA) that is not detected by traditional genetic screening methods has been discovered in patients in Irish hospitals according to research to be published in the journal Antimicrobial Agents and Chemotherapy. These findings provide significant insights into how new MRSA strains emerge and highlight the potential for the transmission of infectious agents from animals to humans.

Not only is this new type of MRSA `distinctly different’ from previously described strains it is not identified as antibiotic resistant by conventional and real time DNA-based polymerase chain reaction (PCR) assays.

Which means that humans (or animals) infected with this strain might be treated with ineffective antibiotics, based on standard testing protocols.

From the press release above:

Commenting on the significance of the findings, Professor David Coleman from the University of Dublin said: "The results of our study and the independent United Kingdom study indicate that new types of MRSA that can colonize and infect humans are currently emerging from animal reservoirs in Ireland and Europe and it is difficult to correctly identify them as MRSA. This knowledge will enable us to rapidly adapt existing genetic MRSA detection tests, but has also provided invaluable insights into the evolution and origins of MRSA."

For more on The Lancet study, we’ve a couple of newspaper reports from the UK.

The superbug MRSA has been found in the milk of British cows for the first time, scientists have warned.

While the impact on human health from this `new strain’ of MRSA has thus far been limited (less than 100 known infections in the UK since 2008), researchers say the rate is increasing each year.

Lead researcher Dr. Mark Holmes, at a news conference on Thursday, was quoted as saying:

"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. This is one of the many things we will be looking into next”

"Drinking milk or eating meat is not a health issue, as long as the milk is pasteurized," he added that the process of making cheese also "generally kills most of the bacteria".

The authors call it a "credible hypothesis" that the overuse of antibiotics in order to increase production of dairy and meat products may be driving the evolution and emergence of these new resistant strains.