Food Safety Evaluation Antibiotic Resistance Genes: A Threat?

A dangerous scenario: Antibiotic resistance genes from GM foods are taken up by bacteria in the gut during digestion. If bacteria carrying antibiotic resistance genes were ever to cause infection, it would be very difficult for doctors to treat. Until now, however, there is no real proof that the antibiotic resistance genes in GM plants pose a threat. Regardless, as a precautionary measure, some experts say that antibiotic resistance genes should not be used.

In the last 15 years there have been numerous scientific studies on this subject. So far nothing threatening has been found. The most important results of these studies are:

• The probability of a successful transfer of an antibiotic resistance gene to a bacterium is very low. Estimates from laboratory experiments place the probability at anywhere from 1:10,000,000,000,000 to 1:1,000,000,000,000,000,000,000,000,000.

• Resistance genes for the antibiotics kanamycin and ampicillin, the most commonly used marker genes, are already widespread in organisms that cause diseases. Tests on the stools of people not taking antibiotics showed that in 60 percent of cases, more than 10 percent of bacteria had resistance to at least one type of antibiotic. Soil tests confirmed that antibiotic resistant bacteria, particularly kanamycin resistant bacteria, are widespread in nature. Even if resistance genes from GMOs were transferred to bacteria in a few cases, the rise in the number of antibiotic resistant bacteria in our environment would be immeasurably small.

• Kanamycin is now rarely prescribed in human medicine. Ampicillin is still used to treat certain infections, but since resistance is so widespread, treatment is usually combined with substances (beta-lactamase inhibitors), which take away the effect of the resistance genes.

• Whenever we eat fruits and vegetables we are eating antibiotic resistant microorganisms from the soil. This has no known negative effects.

Despite these considerations, some still believe that antibiotic resistance markers should not be used at all as a precaution for environmental and consumer protection. It is thought that if GM plants with antibiotic resistance genes are planted over a very large area, the rare event of gene transfer to other organisms (horizontal gene transfer) could become significant.

See also on GMO-Compass:

• Position of EFSA on antibiotic resistance markers: Limited use