A study has found that both humans and their companion animals have the same shared population of methicillin-resistant Staphylococcus aureus (MRSA) bacteria. The study was led by Mark Holmes, senior lecturer in preventive veterinary medicine at the University of Cambridge in England. Holmes said, “Our study demonstrates that humans and companion animals readily exchange and share MRSA bacteria from the same population.” He added, “It also furthers the 'one health' view of infectious diseases that the pathogens infecting both humans and animals are intrinsically linked, and provides evidence that antibiotic usage in animal medicine is shaping the population of a major human pathogen.”

MRSA bacteria are found on skin and can cause infections in both humans and animals that are difficult to treat. For this study, the researchers sequenced the genomes of 46 MRSA samples taken from dogs and cats in the period from August 2003 to August 2007 in the UK. On analysis, it was found that the samples were similar to the MRSA strains found in humans, most of which came from soft tissue infections, skin infections and wound infections. Additional samples were taken the animals’ cerebrospinal fluid, nasal discharge, urine and other sources.

The bacteria were all part of the EMRSA-15 genetic family tree, and nearly all samples were similar to human bacteria genetically. On checking their place in the genetic family tree, it was found that the bacteria in companion animals most likely originated from humans. Also, researchers found results that suggested that MRSA can be transmitted readily in veterinary hospital settings. Holmes said, “It's a reminder that constant vigilance and high levels of hygiene are just as important when treating cats and dogs as with humans.”