Reproduced with permission from The Institute of Science in Society
The following warnings come from a letter from N. Tomlinson of UK MAFF's
Joint Food Safety and Standards Group dated 4 December 1998 to the US FDA,
commenting on its draft document, "Guidance for Industry: Use of
Antibiotic Resistance Marker Genes in Transgenic Plants".
- Exposure of farm workers and food processors to transgenic DNA in
dust and pollen
- Transfer of antibiotic resistant marker genes to gut microorganisms
- Transfer of antibiotic marker genes to environmental organisms
- Transfer of transgenic DNA into mammalian cells
- Ampicillin resistance marker gene may compromise treatment for
The letter from MAFF cites new findings from the University of Leeds
showing "the relative difficulty with which plant DNA is degraded
during processing"(p.4). It mentions other new research showing that
bacteria in the mouth can take up foreign DNA and express the gene(s); and
transformable bacteria are also present in the respiratory tract.
MAFF warns that "there is a case to be concerned about the problem
of gene transfer to environmental organisms" and that bacteria that
have taken up the antibiotic resistance genes "could also act as a
gene pool that may interact with human pathogens." (p.4).
"The widespread use of transgenics carrying antibiotic resistance
marker genes will involve a massive amplification of these genes in the
biosphere. Whether or not these genes are expressed, amplification on the
scale that will occur when transgenic crops are planted in large fields
means that arguments about the rarity of possible transfer events will
become less significant." (p.5).
MAFF cites recent publications showing that transgenic DNA may gain
access into mammalian cells by being carried in pathogenic bacteria that
invade cells. The ampicillin-resistance marker gene encodes a
beta-lactamase which inactivates penicillin and other penicillin-like
antibiotics. This gene is highly mutable, and hence capable of extending
its spectrum of resistence to many other similar antibiotics. "Human
respiratory flora contains notable potential pathogens including Neisseria
meningitidis and Streptococcus pneumoniae. These bacteria do not currently
exhibit high-level, beta-lactamase mediated resistance to penicillins."
Dr. Mae-Wan Ho , a scientists who has been warning of these
possibilities of horizontal gene transfer to unrelated species for several
years, says,"It is irresponsible for the Government to continue with
the massive farm-scale field trials in view of the evidence its own
scientists are taking into account." She points out that transgenic
pollen can travel for miles. Not only farm workers and food processors,
but the general public will also be exposed to transgenic DNA, while bees
will certainly take it up and contaminate the honey.
There is no provision to monitor for horizontal gene transfer or impacts
on health in the current farm-scale trials.
The current farm-scale field trials involve herbicide-tolerant
transgenic maize and canola. The transgenic maize carries a 'disrupted'
ampicilllin-resistance gene, which is not expressed. However, given the
mutability of that gene, it may become re-activated in bacteria.