Some genetically modified plants contain genes that make the plant resistant to certain antibiotics. Scientists often add these resistant genes during genetic modification so that the GM plants and cells can be distinguished from non-GM ones.
In theory when a genetically modified plant is eaten, such genes can be transferred to bacteria in the gastro-intestinal tract of humans or animals. The bacteria could go on to develop resistance to that specific antibiotic. Subsequently that antibiotic could be ineffective in treating humans affected by the resistant bacteria. The risk of such a gene transfer is very small, but it is nonetheless taken into account when assessing applications for, say, field trials or market approvals.
Licence applications for any uses involving GMOs are individually assessed for associated risks, including any potential risk from antibiotic-resistant genes. If the risks are negligible, the application may be approved. The risk assessment can call on advice from COGEM or other expert bodies. Documentation from other international organisations, such as the European Food Safety Authority (EFSA) is also important.