The Food and Drug Administration has recently proposed severe restrictions
on the use of antibiotics to promote the health and growth of meat animals.
Medications added to feeds kill many microorganisms but also encourage the
appearance of bacterial strains that are resistant to anti-infective drugs.
Already, for example, penicillin and the tetracyclines are not as effective
therapeutically as they once were. The drug resistance is chiefly conferred by
tiny circlets of genes, called plasmids, that can be exchanged between
different strains and even different species of bacteria. Plasmids are also one
of the two kinds of vehicles (the other being viruses) that molecular
biologists depend on when performing gene transplant experiments. Even present
guidelines forbid the laboratory use of plasmids bearing genes for resistance
to antibiotics. Yet, while congressional debate rages over whether or not to
toughen these restrictions on scientists in their laboratories, little
congressional attention has been focused on an ill-advised agricultural
practice that produces known deleterious effects.
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