smitty777 writes with news that researchers have discovered another way methicillin-resistant Staphylococcus aureus (MRSA) bacteria are developing resistance to antibiotics. According to the study (abstract), the bacteria made the jump to pigs on livestock farms, developed greater resistance through the rounds of antibiotics commonly used to keep the pigs healthy, and then jumped back to humans. "The important development in the story of ST398 is its move back off the farm into humans, causing first asymptomatic carriage in that original family, and then illnesses in other Dutch residents, and then outbreaks in healthcare settings, and then movement across oceans, and then appearance in retail meat, and then infections in people who had no connection whatsoever to farming—all from an organism with a distinctive agricultural signature. That’s an important evolution, and an illustration once again that, as soon as resistance factors emerge, we really have no idea where they will spread. So it would be a good idea to take actions to keep them from emerging, or at the very least to implement surveillance that would allow us to identify them when they do."