Horizontal gene transfer – DNA being taken up and integrating into the genome of cells – came under scrutiny by the European food Safety Authority (EFSA)  in relation the safety of  antibiotic resistance marker genes in genetically modified (GM) crops grown commercially or entering the market. EFSA failed to reach a unanimous opinion. The published Statement [1] acknowledged scientific uncertainties, but claims it is “unlikely” that antibiotic resistance genes in GM crops pose health and environment risks.

However, two senior scientists on EFSA’s biohazard panel, which carried out the assessment jointly with the GMO panel, did not agree with the conclusion and issued a minority opinion included in an annex to the Statement. The key issue is the probability that the antibiotic resistance genes could transfer from plant to bacteria. The two scientists stated that the adverse effects cannot be assessed, and that the probability of gene transfer from plants to bacteria ranges widely “from unlikely to high.”

EFSA had already given a positive opinion to Germany chemical company BASF’s GM potato that has an antibiotic resistance marker gene, but was asked by the European Commission to re-examine the risks of antibiotic resistance, after failing to address persisting legal and health concerns [2]. An EU law from 2001 requires antibiotic resistance genes that may have adverse effects on human health and the environment to be phased out by the end of 2004, while the World Health Organisation considers the antibiotics inactivated by the resistance gene in the GM potato vital for treating serious infections such as tuberculosis.

Despite the scientific uncertainties, the European Commission granted approval to the GM potato, Amflora in March 2010, in time for the planting season [3], more than 13 years after BASF first applied for commercial approval in the EU.

Conclusion

EFSA’s claim that it is “unlikely” for antibiotic resistance genes in GM crops to pose health and environment risks is based on failure to detect horizontal gene transfer events in the field is  unjustified, in view of evidence from studies that conflict with those on which it has based its conclusion, in particular:

1. Transfer of GM DNA from plant to bacteria has been found both in the field and in the gastrointestinal tract, despite the paucity of dedicated research.

2. Transfer of antibiotic resistance marker genes in the gastrointestinal tract is particularly relevant to human and animal health

3. Recent research based on non-selective direct visualisation of horizontal gene transfer events suggests that previous methods underestimate the true extent of horizontal gene transfer.

4. The antibiotic resistance marker gene nptII is not common in the environment and its release in GM crops can severely compromise antibiotics vital to treating multidrug life-threatening infections

5. EFSA has failed to consider the damage from unsuccessful horizontal gene transfer, which is at least a hundred to a thousand fold that of successful horizontal gene transfer, especially for human and animal cells

6. It has failed to consider evidence suggesting that GM DNA is more likely to transfer horizontally than natural DNA

EFSA needs to consider the full hazards of horizontal gene transfer as a matter of urgency before it considers further environmental releases of GMOs.