The E coli strain that is killing people in Europe is both new and resistant to at least a dozen antibiotics in eight classes. It’s clear, therefore, that this strain picked up resistance via gene transfer from previous strains that evolved resistance over a longer time frame. Thus, antibiotic resistance can spread very quickly, probably more quickly than we can develop new antibiotics. One of the places that resistance develops is in farm animals where antibiotics are used as growth promoters, not just as therapeutics. Since there is a significant externality from antibiotic use, there is a good case to be made for regulating antibiotic use. As Glenn Reynolds once put it:

I think you can make a better case for regulating antibiotics than heroin: Misusing antibiotics can endanger countless others, while misusing heroin mostly endangers oneself.

(FYI, Tyler and I use antibiotic use as an important example of externalities in Modern Principles).

Denmark progressively regulated and reduced antibiotics for sub-therapeutic use in pigs, poultry and other livestock beginning around 1995. After some experimentation, pig production was not adversely affected and resistance in the wild declined. It’s less clear whether human health increased due to the regulation of antibiotics in farm animals (although there is less resistance in countries that use fewer antibiotics). It may be that Denmark is simply too small and connected with the rest of the world to see a large effect. Nevertheless, Denmark shows us that the costs of reducing antibiotic use in farm animals is not excessive, especially if phased-in, and the benefits of maintaining the effectiveness of our stock of antibiotics is so high that I see more intelligent but reduced use as an important goal.

See also Megan McArdle’s very good talk on this topic.