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ANTIBIOTIC RESISTANCE GENES IN TRANSGENIC PLANTS, IN PARTICULAR AMPICILLIN RESISTANCE IN Bt-MAIZE

Executive summary

Oekoinstitut Freiburg on behalf of Greenpeace Germany

1) Introduction

Greenpeace commissioned this report to review the facts about genetically modified plants which contain resistance genes to medically-useful antibiotics. Particularly critical is the Ampicillin resistance gene in the genetically manipulated maize of Novartis. The Europe-wide approval for the planting of this maize line under European gentech-law took place on the 23th of January 1997, against the will of the majority of the EU member states. The first European commercial crop of a genetically manipulated organism is due to be planted in France in April 1998, after the government decided in February to enter Novartis' maize in the national varieties list.

The maize was manipulated to make it resistant to insect damage and herbicides. It also contains an unnecessary antibiotic resistance gene. This report deals with the health risks of such antibiotic resistances that have been generated by means of genetic engineering.


2) Resistance against therapeutically important antibiotics

Usually one speaks of an Ampicillin resistance. Ampicillin belongs to the Penicillin-group of antibiotics, which are still the most commonly used antibiotics in therapy. The artifically introduced gene enables the break-down not only of Ampicillin but also a number of related Penicillins - like Penicillin G, Amoxicillin and some others. These drugs are still used to treat several serious illnesses: for example, Ampicillin is used for the treatment pneumonia, bronchitis and diphteria.

This antibiotic resistant gene has already developed more than 30 years ago and has been developed further since then. Today it's considered as the main origin of a series of antibiotic resistances that have lead to major problems in medicine. For example the present wide spread resistances to a big group of the Cephalosporine antibiotics, which are widely used in therapy and can be put down to the gene that Novartis has now introduced into its transgenic maize.


3) A Transfer of the antibiotic resistance from plant to bacteria is possible. The probability of such a transfer has previously been underestimated.

There is the risk that the gene can be transferred from the plant to disease causing germs, whether the transgenic maize is used as animal fodder or as a food product for humans. These bacteria would then be immune to antibiotic treatment.

This kind of a gene transfer from a plant cell to bacteria is called horizontal gene transfer. Research on if and to what extent such gene transfer can happen has only recently started, so the available scientific data is incomplete.

But one can say definitely that

  • genes can be relatively stable in the intestine;
  • bacteria can in principle take up genes in mammalian intestines;
  • horizontal gene-transfer from genetically modified microorganisms to bacteria has been observed in the intestines of insects (e.g. spring-tails);
  • soil-bacteria are known to take up genes in the soil;

Given the above, current scientific knowledge strongly supports the assumption that antibiotic resistance genes can be taken up from bacteria in the intestines of animals and humans. Genetic engineers often state that gene-transfer of antibiotic resistances is very unlikely ... this statement simply can not be scientifically proven. On the contrary, recent research shows that all preconditions for such gene transfer are now present. Given the fact that huge amounts of possibly genetically modified plants are used for animal feed, and that almost 9% of the US maize harvest in 1997 is genetically modified, the statistical probability of a gene transfer is quite high.

Experience in normal agricultural practice shows that antibiotic resistances can move from animal pathogens to bacteria that are also harmful to humans.


4) At present , antibiotic resistances are not as wide spread in the environment as the genetech industry claims

The risks of antibiotic resistances used in genetic engineering is often trivialized by the industry, with the argument that a large proportion of the bacteria in our environment is already resistant to antibiotics. In their opinion, occasional gene transfers from genetically modified plants to pathogens is statistically insignificant. Several research results contradict this argument. Novartis often states that about 40-60% of intestinal bacteria are already resistant to Ampicillin and related antibiotics. But they present no scientific data for these figures. An analysis of scientific literature shows that the frequency of antibiotic resistances varies considerably. Depending on the variety of bacteria, and also depending on the country where the research has been carried out, the results are completely different. The percentage of antibiotic resistant germs in samples of one variety of bacteria (Bacteroides fragilis) varied between 3 and 30%, in samples of another bacteria (Shigella) between 5,9 and 80,7%. A general statement of 40-60% is completely unfounded. It also has to be assumed that not every human being carries antibiotic or Ampillicin resistant germs. Each antibiotic therapy is based on the bacteria being and staying sensitive to the chosen antibiotic. To maintain the effectiveness of antibiotics as long as possible, it is simply irresponsible to put further resistance genes into circulation.


5) It is an unnecessary, obsolete technology

Novartis' genetically modified maize is an obsolete technology, regardless of the potential danger that the antibiotic resistance gene poses. For several years it has been possible to produce genetically modified plants that do not contain antibiotic resistance genes.

The use of antibiotic resistance genes in transgenic crops does not serve any purpose. Such resistance genes are used as markers in the laboratory by genetic engineers, to distinguish cells where their engineering of other traits has been successful from those where they failed. If the cells are treated with antibiotics after the gene transfer, only those containing the resistance gene survive - those cells also will be the only ones containing the desired genes, like insect- or herbicide-resistance. Today, it is possible to use other markers instead. It is also possible to remove antibiotic resistance genes after the genetic engineering event.

Because they are unnecessary and dangerous, many authorities oppose the use of antibiotic resistance markers. The German ZKBS recommends the renunciation of clinically-important antibiotic resistances. The French Committee of Prevention and Precaution recommends a ban of all transgenic crops containing antibiotic resistance genes. The US Biosafety Advisory Committee says that antibiotic resistances should not be trivialised. Norway prohibits all transgenic plants with antibiotic resistances. The French government will not allow such plants (other than Novartis's already-approved maize). Several EU-member states such as the United Kingdom, pronounced themselves against the approval of the Novartis maize in Europe.


Greenpace demands:

  • Prohibition of all genetically manipulated plants with antibiotic resistances

  • No commercial growing of Novartis maize

  • No deliberate releases of genetically manipulated plants

Report conducted by the Oekoinstitut Freiburg (Germany), Claudia Eckelkamp, Manuel Jaeger, Barbara Weber, on behalf of Greenpeace

Full report available upon request (only in German) .

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