March 31, 2009

Antibiotics in soil affect ecosystems

A Dutch study suggests antibiotics used extensively in intensive livestock production might have an adverse effect on agricultural soil ecosystems.

University of Utrecht researchers led by Heike Schmitt studied the effects of antibiotics passed from animals in manure that was then spread on farmland.

Although higher organisms, such as earthworms, would only be affected at unrealistic concentrations of antibiotics, the scientists said changes in soil bacterial communities have been found repeatedly using molecular microbiological techniques.

The study found bacteria involved in the nitrogen cycle, which replenishes nutrients in the soil, seem to be particularly affected. In addition the microbial population of the soil changed as fungi replaced the bacteria suppressed by the antibiotics.

The antibiotic concentrations that to date have been found in agricultural soils are smaller than the concentrations at which the adverse effects start occurring, said Schmitt, However, this might not be the case for 'hot spots, for example, when manure is not mixed thoroughly in the soil."

He presented the research Monday in Harrogate, England, during a meeting of the Society for General Microbiology.