Sunday, September 22, 2013

Livestock Origin for a Human Pandemic Clone of Community-Associated Methicillin-Resistant Staphylococcus aureus

Livestock Origin for a Human Pandemic Clone of Community-Associated Methicillin-Resistant Staphylococcus aureus


  1. The Roslin Institute and Edinburgh Infectious Diseases, University of Edinburgh, Easter Bush, Midlothian, United Kingdoma
  2. University of Cambridge, Department of Veterinary Medicine, Cambridge, United Kingdomb
  3. Institute of Evolutionary Biology, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdomc
  4. National Food Institute, Technical University of Denmark (DTU), Lyngby, Denmarkd
  5. Microbiology Services, Colindale, Health Protection Agency, London, United Kingdome
  6. Department of Antimicrobial Surveillance and Research, Statens Serum Institute, Copenhagen, Denmarkf
  1. Address correspondence to J. Ross Fitzgerald, Ross.Fitzgerald{at}
  1. Editor Fernando Baquero, Ramón y Cajal University Hospital




The importance of livestock as a source of bacterial pathogens with the potential for epidemic spread in human populations is unclear. In recent years, there has been a global increase in community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections of healthy humans, but an understanding of the different evolutionary origins of CA-MRSA clones and the basis for their recent expansion is lacking. Here, using a high-resolution phylogenetic approach, we report the discovery of two emergent clones of human epidemic CA-MRSA which resulted from independent livestock-to-human host jumps by the major bovine S. aureus complex, CC97. Of note, one of the new clones was isolated from human infections on four continents, demonstrating its global dissemination since the host jump occurred over 40 years ago. The emergence of both human S. aureus clones coincided with the independent acquisition of mobile genetic elements encoding antimicrobial resistance and human-specific mediators of immune evasion, consistent with an important role for these genetic events in the capacity to survive and transmit among human populations. In conclusion, we provide evidence that livestock represent a reservoir for the emergence of new human-pathogenic S. aureus clones with the capacity for pandemic spread. These findings have major public health implications highlighting the importance of surveillance for early identification of emergent clones and improved transmission control measures at the human-livestock interface.

IMPORTANCE Animals are the major source of new pathogens affecting humans. However, the potential for pathogenic bacteria that originally were found in animals to switch hosts and become widely established in human populations is not clear. Here, we report the discovery of emergent clones of methicillin-resistant Staphylococcus aureus (MRSA) that originated in livestock and switched to humans, followed by host-adaptive evolution and epidemic spread in global human populations. Our findings demonstrate that livestock can act as a reservoir for the emergence of new human bacterial clones with potential for pandemic spread, highlighting the potential role of surveillance and biosecurity measures in the agricultural setting for preventing the emergence of new human pathogens.



  • Citation Spoor LE, McAdam PR, Weinert LA, Rambaut A, Hasman H, Aarestrup FM, Kearns AM, Larsen AR, Skov RL, Fitzgerald JR. 2013. Livestock origin for a human pandemic clone of community-associated methicillin-resistant Staphylococcus aureus. mBio 4(4):e00356-13. doi:10.1128/mBio.00356-13.

  • Received 20 May 2013
  • Accepted 14 June 2013
  • Published 13 August 2013

This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-ShareAlike 3.0 Unported license, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original author and source are credited.





Veterinary Record 173:260 doi:10.1136/vr.f5488

  • News and Report

  • Research

Study reveals bovine origin for human MRSA strain

A RECENT study has suggested a type of meticillin-resistant Staphylococcus aureus found in people originated in cattle at least 40 years ago. Researchers say that their work provides clear evidence that livestock were the original source of the MRSA strain, which is now widespread in the human population.
The researchers, from a number of different institutions, including the Roslin Institute and Cambridge veterinary school, …

Tuesday, September 17, 2013

Antibiotic resistance threats in the United States, 2013 THREAT REPORT

“We continue to promote the concept that, if an animal is sick, using antibiotics to treat that animal is obviously important,” said CDC Director Dr. Tom Frieden. “We also know that there are specific situations in which the widespread use of antimicrobials in agriculture has resulted in an increase in resistant infections in humans.”
kind regards,

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