A strain of MRSA that humans can contract from livestock most likely became drug resistant due to the use of antibiotics on the farm. That's according to the authors of a study in mBio this week, who looked closely at the genetic relationships among strains of the antibiotic resistant bacterium MRSA (methicillin-resistant Staphylococcus aureus). They discovered that ST398, a type of MRSA found in livestock that can also be passed to humans was originally a human strain, and it developed resistance to antibiotics once it was picked up by farm animals. The finding illustrates a very close link between antibiotic use on the farm and potentially lethal human infections.
