Unwanted antibiotics may be coming from plants

by Don Gordon
Mankato Free Press
June 13, 2009

In a January column, I discussed how overuse of antibiotics might foster a buildup of disease-causing organisms that are resistant to the chemicals used to control them.

Nearly 70 percent of the antibiotics produced in the United States are fed to livestock, but even if you are a vegetarian there is no escaping them because research conducted at the University of Minnesota confirms we might be getting unwanted antibiotics from plants.

The common vegetables we eat, such as corn, lettuce and potatoes, may absorb antibiotics when grown in soil fertilized with livestock manure.

Now there is new evidence that the ethanol industry may be another source of unwanted antibiotics.

Distillers grain, a byproduct of ethanol production, is a high-protein livestock feed, but according to the FDA and the University of Minnesota, it may be laced with multiple antibiotics. In samples from 60 ethanol plants, including some from Minnesota, FDA chemist Linda Benjamin, said many contained antibiotics such as “penicillin, virginiamycin, erythromycin and tylosin.”

Adding antibiotics is one of several methods used by ethanol manufacturers to control bacterial contamination. These bacteria interfere with yeast in the conversion of carbohydrates to ethanol.

Stan Cox, in an article published last week in the Grand Forks Herald, reported researchers have found antibiotic resistant bacteria in the waste stream of ethanol plants. Cox points out that antibiotics increase ethanol production by 1 to 5 percent, but it is not an absolute necessity as demonstrated by the liquor industry.

I think this news is going to cause some rethinking about recommending distillers grain for the home lawn. With a grant from the Minnesota Pollution Control Agency, distillers grain was tested for two years here in Mankato, and we do know it is an effective pre-emergent herbicide. It has been used for several years on one Minnesota college campus and at some high schools. MSU toxicologist Dr. Steve Mercurio told me this week his major concern over antibiotics in distillers grain is the direct feed to livestock, but there isn’t enough information to access its effect on soil.

Many soil-born organisms are disease causing, and their exposure to more antibiotics might be problematic. In theory, it could also be also be a problem for individuals who are allergic to certain antibiotics if they came in contact with these soil-applied chemicals.

(See also "Worried about Antibiotics in Your Beef? Vegetables May Be No Better" in Scientific American, Jan. 6, 2009.)