|Stray seeds had antibiotic-resistance
Nature, Published online: 29 March 2005, Colin Macilwain,
Accidental release of genetically-modified crops sparks
Hundreds of tonnes of genetically modified corn seeds
sold to farmers by mistake over the past four years
contained a gene for antibiotic resistance, Nature has
learned. The release of such genes into the environment
is sometimes considered inadvisable, as there is a small
chance that they could flow from crops to microorganisms
and spread problems of antibiotic resistance.
The Swiss biotechnology company Syngenta admitted last
week that it had accidentally released a variety of
corn (maize) called Bt10 between 2001 and 2004. Like
other crops with the name Bt, this corn had been genetically
modified to produce a protective pesticide. But Bt10
has not been approved for sale by regulatory agencies.
Officials at the company last week argued that Bt10
is basically identical to Bt11 corn, which has been
approved for sale (see Nature 434, 423; 2005). But this
week, Sarah Hull, a spokeswoman for Syngenta, confirmed
that a marker gene that confers resistance to ampicillin,
a commonly used antibiotic, was present in the Bt10
seeds. She adds that this gene would not have been active
in the corn plants that grew from the seeds.
Antibiotic-resistance genes are widely used as 'tags'
during the production of genetically modified crops,
to help breeders identify and preserve desirable strains.
But the genes are often removed before the seeds enter
the food chain. The presence of the marker gene in Bt10
corn was noted in a 2003 advice notice from a UK government
committee, the Advisory Committee on Releases to the
Environment, which was using Bt10 as a comparison to
prove that there were no marker genes in Bt11 corn.
Critics have expressed surprise that neither Syngenta
nor the US Environmental Protection Agency (EPA) announced
the presence of the marker when they admitted that the
release of Bt10 had taken place. "It is quite scandalous,"
says Greg Jaffe, head of the biotechnology project at
the Center for Science in the Public Interest, a pressure
group in Washington DC. "This shows that the government
and the company are not being forthright."
Hull says that the company didn't mention the gene's
presence because "it wasn't relevant to the health
and safety discussion". She adds that the antibiotic-resistance
genes have been around for a long time. "They've
been studied extensively, and they pose no risk to humans
or animals," she says. Regulators say that the
genes present a very small risk to human health, either
directly - if in the stomach of a patient on antibiotics,
for example - or indirectly through gene flow into microbes.
Michael Rodemeyer, director of the Pew Initiative on
Food and Biotechnology, a think-tank in Washington DC,
says that the presence of such genes would be unlikely
to see a crop declared unsafe in the United States -
but adds that it could cause problems in Europe.
In a ruling published last April, for example, the
European Food Safety Authority, which advises European
Union governments on food issues, said that marker genes
conferring resistance to ampicillin "should be
restricted to field trials and not be present in genetically
modified plants placed on the market". And the
Codex Alimentarius Commission, the international food-standards
body, has urged the agricultural biotechnology industry
to use alternative methods to refine genetically modified
strains in the future.
The EPA, which is jointly investigating the release
of the Bt10 corn with the US Department of Agriculture,
declined to say what it knew about the antibiotic-resistance
marker. "What the company told us and when about
the marker gene is part of our ongoing investigation
and we are not able to discuss it at this time,"
the agency said in a statement.
"I think they've done a terrible job," says
Margaret Mellon, head of the food and environment programme
at the Union of Concerned Scientists in Washington DC,
referring to both Syngenta and the government agencies.
"There are lots and lots of unanswered questions,
and the longer they remain, the less confidence people
are going to have in the technology and in the regulatory