In his comprehensive and highly readable online "Textbook of Bacteriology", Dr Kenneth Todar, an emeritus lecturer in Microbiology at the University of Wisconsin-Madison, calls this a "double hit", because "...we get antibiotics in our food and drinking water, and we meanwhile promote bacterial resistance".
For this reason, the European Union
and other industrialized nations, have banned feeding antibiotics to animals, and recently, the US Food and Drug Administration
(FDA) started urging farmers to limit their use of antibiotics.
In fact, after decades of deliberation, it appears the FDA
may be poised to issue its tightest guidelines yet on use of antibiotics in animals, with the intention of bringing to an end the use of the drugs simply to make animals grow faster.
says that the "non-therapeutic use of antibiotics in livestock production makes up at least 60 per cent of the total antimicrobial production in the United States", so this is not a small thing.
Another industry that is starting to be a cause for concern is genetically modified crops, because some have antibiotic-resistant genes inserted as "markers".
The marker genes are introduced into the crop plant during the early stages of development for scientific reasons (eg to help detect herbicide-resistant genes), but then serve no further purpose, and are left in the final product.
Some people have criticized this approach because they say it could be a way for microorganisms in the environment to acquire the antibiotic-resistant genes.
says that in some cases, these "marker genes confer resistance to front-line antibiotics such as the beta-lactams and aminoglycosides".