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By Root 1259 0

are exceedingly remote, the question of antibiotic-resistance markers also exists in a regulatory vacuum. Attempts to regulate transgenic antibiotic resistance began in 1990, when Calgene, an agricultural biotechnology company, asked the FDA for an opinion about whether it could use a gene for resistance to the antibiotic kanamycin (neomycin) as a selection marker for constructing transgenic tomatoes and canola oilseeds. This particular resistance gene specifies production of an enzyme able to inactivate kanamycin and related antibiotics. By the time the FDA issued its 1992 policy on genetically engineered plants, kanamycin already was in use as a selectable marker for development of more than 30 transgenic crops. In that policy, the FDA made no particular recommendation about antibiotic-resistant marker genes but said that its scientists were evaluating the issue.18 In 1993, hoping to elicit a decisive response, Calgene petitioned the FDA to permit use of the kanamycin-inactivating enzyme as a “food additive” in genetically modified foods and cotton. In 1994, the FDA convened a meeting of its Food Advisory Committee to consider the Calgene petition.

I was one of four consumer representatives to that committee at the time, all of us united in what turned out to be the minority opinion. We were troubled by the lack of satisfactory answers to our questions about the probability of transferring antibiotic resistance. We urged caution but were heavily outvoted. After the meeting, FDA officials correctly reported that committee members “generally” approved the agency’s regulatory approach and agreed that Calgene had addressed the relevant scientific questions. Thus, the FDA ruled that Calgene’s evidence met the legal definition of safety for food additives: reasonable certainty that no harm would result from use.

Calgene contended that the kanamycin-inactivating enzyme (like all enzymes, a protein) would be destroyed by cooking or normal digestive processes and was unlikely to function in the intestine. But could the gene for antibiotic resistance jump from food or soil to bacteria in the intestines of animals or people? The FDA considered this suggestion too highly improbable to be worth discussion. In approving the kanamycin-inactivating enzyme as a food additive, the FDA explained that its policy is not to regulate genes or DNA: “DNA is present in the cells of all living organisms, including every plant and animal used for food by humans or animals, and is efficiently digested. . . . The DNA that makes up the [kanamycin-resistance] gene does not differ from any other DNA and does not itself pose a safety concern.”23

In its decision, the FDA emphasized that safety “does not—and cannot—require proof beyond any possible doubt that no harm will result under any conceivable circumstance.” Nevertheless, the agency agreed to consider further requests for use of selection markers for resistance to other antibiotics on a case-by-case basis. Subsequently, various groups challenged the FDA about the safety and regulatory status of antibiotic-resistance marker genes and, in late 1996 and early 1997, the agency consulted with outside experts about whether the use of such genes might cause problems. On the basis of those discussions, the FDA drafted a guidance statement for industry. This reassuring document said that antibiotic-resistance genes in food were “not of great concern,” as the chance that they might be transferred from plants to bacteria in the intestine or environment was “remote.”24

It is difficult to know how to interpret the FDA’s decisions or guidance suggestions. Either transgenic transfer of antibiotic resistance is a problem or it is not. The FDA’s use of the word “remote” suggests that marker genes require no special attention, but its nonbinding guidance document advises developers to evaluate the use of these genes quite carefully. Developers of new plant varieties, according to the FDA, should find out whether their marker genes involve clinically important antibiotics and whether they could transfer resistance