We can't be too hard on cows and chickens, people are doing the same thing, and in far greater quantities. We use a lot of antibiotics.
Organic company marketing departments and their environmental corporation allies have capitalized on the use of antibiotics in livestock, and in many cases, misrepresented it - the NRDC filed a lawsuit over antibiotic use for growth in 2011 but when California tried to pass a law mandating no antibiotics for growth and letting farmers revert to FDA guidelines for medical use, the NRDC lobbied against it and admitted it antibiotics for growth is actually a tiny percentage of outlier farms and so the law would not help. They may only recently be confused but to microbiologists the origins of antibiotic resistance, and how much of it is man-made, was unclear.
It got less unclear in a recent paper in Proceedings of the National Academy of Sciences by microbiologist Professor Jo Handelsman and colleagues. Instead of implicating corporation farms and antibiotics, they found that organic manure was letting more resistant bacteria gain a foothold in the environment.
What gives? Science has long known that antibacterial resistance has never been as simple as environmental fundraising brochures claim - such as 'get rid of X and the environment is saved'. Bacteria in the environment have always naturally developed antibiotic-resistance genes because soil has always carried antibiotics, due to the influence of fungi, molds and bacteria in the ecosystem. Alexander Fleming discovered penicillin in 1928 because he found that mold inhibited bacterial growth naturally. So blaming modern medicine for antibiotic resistance in soil with certainly was environmental marketing, but not science.
The authors of the new study wanted to find out if man-made antibiotics were really the problem. So they did a study treating soil samples with manure from cows that never had antibiotics, and manure that had the presence of a nitrogen-based fertilizer. Then they examined the samples for the enzymes produced by bacteria that are responsible for resistance to antibiotics like penicillin - called beta-lactamases.
After two weeks, the results were clear - the organic manure was causing more antibiotic resistance by producing more β-lactamases in the soil and that was causing resistant bacteria to flourish.
Environmentalists shouldn't be too disheartened by the results. Even if organic manure causes more antibiotic resistance in the environment, there could be other issues they could blame on humanity.
What they cannot do is dismiss Handelsman as a shill for Big Ag - since 2013, she has been on leave of absence from Yale so she could serve as the Obama administration associate director for science at the White House Office of Science and Technology Policy, led by Obama Science Czar Dr. John Holdren.