Animal Feed and Resistant Bacteria

The use of antibiotics in livestock feed contributes to the growing problem of antibiotic resistance in humans, according to an editorial in this week's issue of the journal Science. Dr. Wolfgang Witte of the Robert Koch Institute, Wernigerode, Germany, argues that this meat industry practice is a "driving force" behind the development of antibiotic resistance in certain species of bacteria that cause human disease. The major purpose of giving antibiotics to cows, sheep, and other livestock is to promote growth. "Animals receiving antibiotics in their feed gain 4% to 5% more body weight than animals that do not receive antibiotics," Witte explains. The antibiotic-resistant bacteria that develop can easily be transmitted to humans through meat or through human contact with living animals.

In some cases, antibiotic resistance is making it difficult for physicians to treat disease. For example, some strains of Salmonella bacteria, which can be transmitted to humans through food or contact with animals, are now resistant to commonly used antibiotics. Last year, the World Health Organization recommended that antibiotics should not be used as growth promoters in animals if there is a risk that humans will develop resistance. Witte points out, however, that a UK commission reached the same conclusion in 1969, and that the meat industry has been debating it ever since. Certainly there are financial incentives for the meat industry to continue using antibiotics as growth promoters. However, Witte points out that in Sweden, where this practice was prohibited in 1986, "improved hygiene has recouped the productivity losses." Because meat products are traded around the globe, worldwide surveillance by pharmaceutical companies and licensing authorities is needed, Witte emphasizes. "In the long run," he predicts, "an industrial investment in alternatives to antimicrobials for animal growth promotion should pay off in more efficient production of food animals as well as protection of the fragile resources that are critical to successful management of human infectious disease."

SOURCE: Science (1998;279:996-997); Reuter’s News Service, 1999