Antibiotic resistance marker genes are used as a tool to recognise the successful introduction into plant cells of a new gene with beneficial characteristics. The markers are coupled with the new gene, so by selecting those cells that express the resistance marker, the cells that have incorporated the gene of interest into their DNA can be identified. Plants derived from these cells neither contain nor produce antibiotics.
The issue of the safety of incorporating antibiotic-resistance markers into GM plants has been a matter of public debate since the early stages of their development. Concern has surrounded the possibility that antibiotic-resistance genes might be passed from GM plants to bacteria, thus creating bacteria that are resistant to antibiotics such as those used to treat common skin, ear, and eye infections.
In this review, authors Stephen Gillespie (University College, London) and Philippe Gay evaluate the scientific evidence regarding the impact of antibiotic-resistance markers on human health. They consider the biological barriers to the transfer of antibiotic-resistance markers into bacteria that cause disease in animals and humans, and the possible clinical consequences of this transfer.
The authors conclude that whereas there is no evidence that antibiotic resistance from GM crops is being transferred to bacteria, this does not exclude the possibility that it might occur. However, the evidence suggests that, if it occurs at all, the contribution to the burden of antibiotic resistance from GM plants is low, and is dwarfed by inappropriate prescribing of antibiotics in medical practice and their use as animal growth promoters in agriculture.
Professor Gillespie comments: "antibiotic-resistance markers do not pose a substantial risk to human health because the contribution that recombinant bacteria might make--should the enormous barriers to transfer be overcome--is so small that any contribution to antibiotic resistance made by GM plants must be overwhelmed by the contribution made by antibiotic prescription in clinical practice."
Contact: Professor Stephen Gillespie, University College London, Hampstead Campus, Rowland Hill Street, London NW3 2PF, UK. T) +44 (0) 20 7794 0433
E: s.gillespie@medsch.ucl.ac.uk
Journal
The Lancet Infectious Diseases