Scientists at the University of Minnesota have been evaluating the
impact of antibiotic feeding in livestock production on the environment.
This particular study, funded by the United States Department of Agriculture
(USDA), evaluated whether food crops accumulate antibiotics from soils
spread with manure that contains antibiotics.
Results from the study are published in the July-August 2007 issue of
the Journal of Environmental Quality. The research was also presented in
Indianapolis, IN at the Annual Soil Science Society of America Meeting in
November 2006.

Plant uptake was evaluated in a greenhouse study involving three food
crops: corn, lettuce, and potato. Plants were grown on soil modified with
liquid hog manure containing Sulfamethazine, a commonly used veterinary
antibiotic. This antibiotic was taken up by all three crops. Concentrations
of antibiotics were found in the plant leaves. Concentrations in plant
tissue also increased as the amount of antibiotics present in the manure
increased. It also diffused into potato tubers, which suggests that root
crops, such as potatoes, carrots, and radishes, that directly come in
contact with soil may be particularly vulnerable to antibiotic
contamination.

The ability of plants to absorb antibiotics raises the potential for
contamination of human food supply. However, Satish Gupta, group leader
notes ?The adverse impacts of consuming plants that contain small quantities
of antibiotics are largely unknown?. Consumption of antibiotics in plants
may cause allergic reactions in sensitive populations, such as young
children. There is also concern that consuming antibiotics may lead to the
development of antimicrobial resistance, which can render antibiotics
ineffective.

Holly Dolliver, the lead scientist in this study, notes that
antibiotics consumed by plants may be of particular concern to the organic
farming industry. Manure is often the main source of crop nutrients for
organic food production, since regulations prohibit the use of synthetic
fertilizers. According to the USDA, producers must manage animal materials
in a manner that does not contribute to contamination of crops by residues
of prohibited substances, which includes antibiotics. However, manures
containing antibiotics are not formally banned or prohibited.

Further research is needed to investigate the presence of antibiotics
in edible parts of plants, especially vegetables that are consumed raw, and
how different plants absorb different antibiotic compounds. Research is
ongoing at the University of Minnesota to further investigate the potential
fate and transport of antibiotics introduced to the environment from
livestock operations.


[www.eurekalert.org]