January 27, 1999
'Superbugs' possible from genetically modified food
'Superbugs' possible from genetically modified food
Fears that genetically-modified foods might promote drug-resistant
"superbugs" have been fuelled by new research.
Dutch scientists used a computer-controlled artificial gut to show that
DNA remains intact for several minutes in the large
intestine.
Hub Noteborn, of the State Institute for Quality Control of Agricultural
Products in Wageningen, said in New Scientist
magazine: "It was a surprise to see that DNA persisted so long in the
colon."
This persistence means it might be possible for genes to jump from
genetically-modified (GM) food into bacteria in the gut
of farm animals. Previously some scientists have said there was no risk
as the modified DNA breaks down too quickly.
If the transferred genes were the antibiotic-resistance genes used as
markers in some GM crops fed to livestock, then
serious health risks might result. The danger would be that
antibiotic-resistant microbes would spread from animals to
humans.
The experiments used bacteria genetically modified to contain
antibiotic-resistant genes. As these were digested in the
artificial gut, half the DNA survived for six minutes.
"This makes it available to transform cells," said Robert Havenaar, of
the TNO Nutrition and Food Research Institute in
Zeist. His team designed the artificial gut which provides a mechanical
model of the stomach and intestines and contains
the normal microbes and enzymes.
For the first time the experiments measured the rate of transfer of DNA
from GM bacteria to other bacteria normally
found in the gut. Only one in 10 million passed on the DNA. But there
are usually around a thousand billion gut bacteria,
suggesting many would be transformed.
However, the Flavr Savr tomato, engineered by Calgene to resist rot, did
not pass on antibiotic resistant genes, although
up to 10% of its DNA reached the colon.
The crucial test will be whether GM foods and bacteria which have
infected the gut can transfer genes. Havenaar says
he will ask the European Union to fund further research.
The new findings show more research is essential, says Derek Burke,
former chair of Britain's Advisory Committee on
Novel Foods and Processes. "We can only say that the risk is not zero,"
he says. "Anything that would help put numbers
on this, would be useful."
A UK House of Lords select committee recently said that the potential
benefits from genetically modified crops far
outweigh the risks. However, they still recommended that the use of
antibiotic-resistance genes in crops such as the
maize fed to some US cattle should be "phased out as quickly as
possible".
--
Judith Richards, London, Ontario, Canada
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