Herbicides can cause bacteria to become resistant to antibiotics
March 24, 2015
Research lead by a team from the University of Canterbury has found that commonly used herbicides can cause bacteria to
become resistant to antibiotics.
Herbicides are used to kill plants. They can be tested for killing bacteria, too, as part of the process of reviewing
their approval for use. However, they have never been tested for other effects on bacteria, University of Canterbury’s
Professor Jack Heinemann says.
This is the first study of its kind in the world. While other substances such as aspirin have been shown to change
bacteria's tolerance to antibiotics herbicides have never been tested. The team at the University of Canterbury
investigated what happens to species of disease-causing bacteria when they are exposed to common herbicides such as
Roundup, Kamba and 2,4-D.
“We found that exposure to some very common herbicides can cause bacteria to change their response to antibiotics. They
often become antibiotic resistant, but we also saw increased susceptibility or no effect. In most cases, we saw
increased resistance even to important clinical antibiotics,” Professor Heinemann says.
“We were so surprised by what we were seeing. We wanted to be sure it wasn’t an artefact of conditions in our laboratory
or some kind of contamination. So we enlisted a fellow researcher at Massey who conducted the same experiments but
without knowing what she was adding to the bacteria. She got the same results.”
The effects found are relevant wherever people or animals are exposed to herbicides at the range of concentrations
achieved where they are applied. This may include, for example, farm animals and pollinators in rural areas and
potentially children and pets in urban areas. The effects were detectable only at herbicide concentrations that were
above currently allowed residue levels on food.
Antibiotic resistance is a serious and growing problem for human and animal health. New antibiotics are hard to find and
can take decades to become available. Effects of chemicals such as herbicides could conflict with measures taken to slow
the spread of antibiotic resistance.
The research team included researchers from Mexico, Lincoln University and Massey University.