The rise of antibiotic-resistant bacteria, including the killer Methicillin-resistant Staphylococcus aureus (MRSA), has been partially blamed on the use of antibiotics in animal feed. Intended to keep livestock healthy, the continuous antibiotic exposure allows bacteria to adapt and evolve into resistant strains.
This effect, however, is not restricted to livestock fed high-antibiotic diets. New research published in PLoS ONE found that nearly 65 percent of grocery store pork labeled “antibiotic-free” harbored Staph, and some 6 percent carried MRSA itself. The label “antibiotic-free” is unregulated.
How the bacteria are getting into the meat and whether they’re then extending their reach to the table is not yet known. Do the animals catch the bacteria at the farm? The processing plant? "The definitive study would take every bacterium and follow that along until it gets in humans—from food supply to causing a certain disease," epidemiologist Tara Smith from the University of Iowa College of Public Health told ScienceNOW.