A shared population of methicillin-resistant Staphylococcus aureus (MRSA) bacteria circulates both in humans and companion animals, according to a study published recently in mBio. “Our study demonstrates that humans and companion animals readily exchange and share MRSA bacteria from the same population,” says senior author Mark Holmes, PhD. MRSA naturally lives on the skin and also causes difficult-to-treat infections in humans and animals. “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.”
Holmes and colleagues sequenced the genomes of 46 MRSA samples from cats and dogs, collected between 2003 and 2007 from veterinary hospitals and practices in the United Kingdom. The samples were found to be similar to those associated with MRSA strains in humans, with most coming from wound infections or skin and soft tissue infections. Additional samples were from the animals’ urine, cerebrospinal fluid, nasal wash or discharge, and bloodstream, heart valve, or joint infections.
Comparing the samples to a global collection of human MRSA samples sequenced as part of other studies and evaluating the evolution of the bacteria, the investigators found that all animal infections fell in the same family: Epidemic MRSA 15 (EMRSA-15) (sequence type ST22), a common strain of MRSA first detected in the UK in the 1990s that spread throughout Europe. The bacteria were interspersed throughout the EMRSA-15 genetic family tree. Nearly all samples were genetically similar to human bacteria, and their place in the family tree showed that the companion animal bacteria most likely originated in humans. Read the article.
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