Current issues on the use of antibiotic resistance genes

Part of the worldwide debate about genetically−modified organisms focuses on the safety of antibiotic resistance gene markers in crops destined for human and animal consumption. Diverse and, in some cases, contradictory opinions have been voiced. At times, the debate has been unhelpful and polarized. One of the problems is that despite an increasing body of scientific knowledge about genetic modification, the opinions put forward have often been based on perception and emotion, rather than scientific rationale.

In response to these concerns, scientists have focused efforts on identifying potential risks to the ecology, resistance management and food biosafety. The results should allow more informed decisions to be made with respect to this technology.

Engineered antibiotic resistance genes in products for consumption

Several commercial transgenic crops in development or production contain antibiotic resistance genes as part of their new genetic make−up. For instance, crops contain genes whose products confer resistance to kanamycin (the nptII gene), spectinomycin and streptomycin (the aad gene), and ampicillin (the bla gene). Concerns have been raised about whether this may lead to an increase in the occurrence of microbial populations resistant to antibiotics, thereby posing a risk to animal and human health.

Most antibiotic resistance genes used in biotechnology were originally isolated from bacteria. To be used in plants these genes undergo a series of modifications: regulatory elements in the DNA sequence are exchanged for those used in plant cells, and usually the gene sequence is also altered to reflect the preferred codon usage of plants. This would make horizontal gene transfer back to bacteria unlikely.

For further information, a list of recent scientific papers discussing the potential of horizontal transfer of genes from plants to bacteria present in the gut of humans or animals and other related issues has been compiled. The list is neither exhaustive nor comprehensive, but is representative of the research in this area.