A new strain of the MRSA superbug has been found in hospitals in Dublin and in the milk of cows in Britain.
Researchers say the organism is different from any discovered since the 1960s and the task of dealing with this superbug in hospitals will become more difficult.
MRSA, or methicillin-resistant Staphylococcus aureus, is a drug-resistant form of a usually harmless common bacterium that can be deadly when it infects wounds.
There is a strong suggestion that the new strain originated in animals.
The findings were established by two teams of researchers in Dublin and Cambridge.
They 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 humans.
The researchers said the new bug is treatable by antibiotics and is not particularly virulent.
The research is published today in the journal, The Lancet Infectious Diseases.