Researchers from the University of Edinburgh, Scotland, analyzed around 40 strains of the bacterium - Staphylococcus aureus, which is capable of building up methicillin antibiotic resistance, leading to MRSA.
Staphylococcus aureus spreads easily in humans through skin-to-skin contact.
The researchers found that at least two genetic subtypes of the bacterium, already present in widespread human MRSA, could be traced back to cattle.
The study, published in the journal mBio, suggests that the bacterium may have passed from cattle to humans by way of direct contact, possibly through people working with farm animals.
Professor Ross Fitzgerald of the Roslin Institute at the university and lead study author, said:
"Human infections caused by bacteria being transmitted directly from livestock are well known to occur.
However, this is the first clear genetic evidence of subtypes of Staph. aureus which jumped from cattle and developed the capacity to transmit widely among human populations."
Bacteria developed resistance when passed to humans
Are they the culprits? Researchers say a type of MRSA in humans may have come from cows.
The researchers explain that once the bacterium was passed on to humans, Staphylococcus aureus became resistant to methicillin - a class of antibiotics in the penicillin group.
The bacterium also progressed to form the ability of avoiding attack from the human immune system. But the study authors add that the bacteria originating in the cattle do not seem to be any more aggressive or have stronger resistance to antibiotics compared with other forms of MRSA in humans.
"This research provides insight into how some strains of MRSA have evolved and help us better understand how they have adapted to cause disease in different host species," added Laura Spoor, also of The Roslin Institute at the university.
Good hygiene measures may prevent spread
Many infectious diseases in humans are thought to have stemmed from animals. For example, a recent European study suggested that the MERS coronovirus may come from camels.
The researchers of this most recent study highlight the importance of hospitals acting on the importance of hygiene in preventing transmission of pathogens such as MRSA. Research has shown lower MRSA rates in hospitals that take infection control seriously by having a board-certified director.
The study authors conclude that improved hygiene measures when humans are handling livestock may also help to limit transmission:
"Improved biosecurity and hygiene control measures which prevent the spread of bacterial flora between livestock and human hosts may limit opportunities for successful livestock-to-human transmission."
"Furthermore, regular surveillance of the microbiota in livestock and humans may facilitate the early identification of emergent clones with the capacity to transmit and cause disease among human populations."