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roundtable: the evolving enemy Watch Show 4:
"The Evolutionary Arms Race"
on PBS
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bottle of prescription antibiotics
In the battle against infectious disease, humankind has inadvertently given rise to deadly enemies. Antibiotic resistance is a stunning example of evolution by natural selection. Bacteria with traits that allow them to survive the onslaught of drugs can thrive, re-ignite infections, and launch to new hosts on a cough. Evolution generates a medical arms race. The bad news is that bacteria -- with their fast doubling times and ability to swap genes like trading cards -- evolve quickly. The good news is that in the 150 years since Darwin, we have grown to understand the rules of the race. But can we win this war?
Tamar Barlam
  George Beran
  Stuar Levy
  Stephen Palumbi
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George W. BeranGeorge W. Beran is distinguished professor of preventive veterinary medicine at Iowa State University in Ames, Iowa. His research and teaching career has been in the epidemiology of antimicrobial resistance and diseases transmitted between animals and humans through foods of animal origin. He was a member of the National Research Council Committee on Drug Use in Animals.

Antibiotics are very important in the health and production of animals, as they are in human health. But, antibiotic use leads to the selection of resistant bacteria which can be transferred between people, between animals, but also from animals to humans (and vice versa).

In pet animals, antibiotics control and shorten diseases, and prevent infection of other animals and infection from animals to people. But, the antibiotics that work best for pets are basically the same or similar to those used for humans -- which increases the risk of transferring resistance between animals and humans.
In food animals, antibiotic use for the purpose of disease therapy and prevention is advantageous since it decreases suffering, increases productivity, and protects people, other animals, and the environment from transfer of pathogenic bacteria. Preventive low-level feeding of antibiotics to food animals is useful for increased animal growth, since it suppresses bacteria, but antibiotics should be carefully selected for their effectiveness in the specific species of animals and for their use at critical stages in the animals' growth.
Antibiotics also enhance food animal growth by suppressing bacteria competing for nutrients, maintaining a thinner, more absorptive intestinal mucosa, and favorably modifying the intestinal bacteria. Their use is an effective adjunct to -- but not a substitute for -- optimal management, control of exposure and stress, nutrition, and sanitation in the food animal industry. There is also a move in the industry toward the increased use of antimicrobials that are not used in human medicine. Other methods of fighting disease and increasing productivity in food animals are in development, such as vaccination, immune enhancement measures, enhanced nutrition, and genetic selection.
Judicious use of antibiotics in food animals, pet animals, and human patients is crucial. The monitoring of resistant strains in all of these populations, however, must also be enhanced.
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