The human origins of "pig" Staph ST398

[Gert van der Hoek]

The human origins of "pig" Staph ST398


Bacteria, including multiresistant bacteria are freely shared between humans and animals. These bacteria jump to animals and jump back.

New research says you can't simply say: MRSA or "Pig MRSA" is caused by the overuse of antibiotics in the pig industry. It seems to be more complicated.

The findings throw the ST398 story a bit on its head. Instead of being a true pig strain, ST398 appears to have originated as a methicillin-susceptible human strain which was transferred into the pig population, picked up antibiotic resistance genes (including resistance to methicillin and tetracyclines), and then has been passed back to farmers as more resistant organisms. Some prophages were also gained or lost along the way, probably due to selection by host factors.

Indeed, it looks like ST398 has taken a very similar path to that of another animal-associated S. aureus strain, ST5. As Ed Yong described back in 2009, humans are also the ultimate origin of a "chicken" type of S. aureus ST5, which spread around the world in broiler chicken flocks. In Ed's article, the first author of the chicken ST5 paper, Bethan Lowder, notes that the change in chicken farming from small farms to multinational corporations likely aided the spread of this organism--and the exact same thing has happened with pig farming.

Scienceblogs

thanks to Mike Coston