Position of EFSA on Antibiotic Resistance Markers Limited Use

In the EU, GM plants with certain antibiotic resistance markers have been given only limited authorisation for release into the environment.

On 2 April 2004, the GMO Panel, a committee of experts under the European Food Safety Authority (EFSA), submitted a report on antibiotic resistance marker genes. According to the experts, a general ban on the use of antibiotic resistance marker genes is not justified. Nonetheless, EFSA suggests a careful approach to their use on an individual basis: some should be not be used at all, and others should be used on a limited basis. The nptII marker gene, which is used in most GM plants and imparts resistance to kanamycin, may continue being used without restriction.

Young transgenic plants. Kanamycin resistance is widely used to create genetically engineered plants. The use of this marker is to remain permitted.

Avoiding risk as a precaution Although the chances of horizontal gene transfer from genetically modified plants to microorganisms are very small, EFSA’s GMO Panel works upon the basis that it is possible when evaluating the safety of various antibiotic resistance genes (ABR genes). The experts on the GMO Panel haven taken the position that marker genes should do no damage to the environment or to human or animal health if horizontal gene transfer were to occur. Several criteria are considered when evaluating antibiotic resistance genes: The medical importance of the antibiotic concerned. The distribution of microorganisms already possessing resistance genes in soil and water, as well as their presence in the digestive tracts of humans or other mammals.

Different markers, different approaches

EFSA’s GMO panel classifies the ABR marker genes in three groups:

• First group: Unlimited use.
  According to EFSA, these marker genes can continue being used in GM plants. The antibiotic resistance genes in this group are widespread in nature and their corresponding antibiotics are seldom or never used in medicine. The nptII gene (kanamycin resistance) falls under this category.

• Second group: Not to be used in commercial GM plants.
  Plants possessing these genes may be planted in field trials, but they may not be used for agriculture. These genes confer resistance to antibiotics used in human and veterinary medicine to treat specific infections. These resistance genes are widespread in microorganisms. According to the committee, growing plants with genes from this group would not increase the distribution of resistance genes in nature. The ampicillin resistance gene fits into this category.

• Third Group: Not allowed.
  These marker genes are to no longer be used in GM plants. They confer resistance to antibiotics that are of high value, particularly in human medicine. The effectiveness of these antibiotics must not be compromised. One example of this type of gene is the nptIII gene (resistance to amikacin).

Use Restricted By Law: EFSA’s report on antibiotic resistance markers was conducted in light of the EU directive on the deliberate release into the environment of genetically modified organisms (2001/18/EC) that came into effect in October 2002. The directive demands that antibiotic resistance marker genes be monitored and used with caution.

Article 4 of the directive states:

„Member States and the Commission shall ensure that GMOs which contain genes expressing resistance to antibiotics in use for medical or veterinary treatment are taken into particular consideration when carrying out an environmental risk assessment, with a view to identifying and phasing out antibiotic resistance markers in GMOs which may have adverse effects on human health and the environment. This phasing out shall take place by the 31 December 2004 in the case of GMOs placed on the market according to Part C and by 31 December 2008 in the case of GMOs authorised under Part B.“

See also on GMO-Compass:

• Antibiotic Resistance Genes: A Threat?