Canterbury: 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.
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.