Antibiotics And Drug Resistance In Animals

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Most people are aware of the dangers of antibiotics, even those who advocate them.  Issues such as antibiotics creating drug resistance and destroying the healthy flora in the gut are recognized by most vets and pet owners.

Researchers  at the USDA Agricultural Research Service’s National Animal Disease Center have recently discovered that not only does antibiotic use in pigs change the bacterial flora in the gut, even low doses of the drug given for only two weeks causec a drastic increase in the number of E-coli bacteria in the gut.  Moreover,  those bacteria showed a large jump in resistance to antibiotics.

“We wouldn’t have been surprised that bacteria shift populations or that resistance genes changed,” said Thad Stanton, the microbiologist leading the study in Ames, Iowa. “We were a little surprised by how much E. coli populations went up in the medicated group. We were so surprised that we did a repeat experiment in culture. And the number went up by 20 to 100-fold. That’s a big change.”

“We have to be judicious in antibiotic use,” he added. “We are going to need to work together on this, and we need research to discover alternatives.”

Previous studies on farm animals have shown that antibiotic use leads to an increase in antibiotic resistance in animals taking the drugs as well as in people working on the farms where those animals live. Even when farmers stop using the drugs, resistance persists for years, as mothers pass their drug-resistant flora down to their offspring for generations.

Because animals shed their gut bacteria through their feces, which often get spread all over fields, antibiotic use in agriculture has raised worries about the spread of untreatable epidemics throughout the human population. The FDA is currently changing the way it regulates the practice.

The same thing could be happening in your yard, parks or dog boarding and training facilities where the feces are tracked by you, your dog and even your children.

In the USDA study, bacteria in both medicated and non-medicated pigs held multiple genes that conferred resistance to antibiotics, according to DNA analyses. What is frightening is that treatment with antibiotics produced resistance not just to the drugs the pigs were eating. Genes also flourished that could resist other kinds of antibiotics as well, and researchers are now puzzling over the details of how using just a few antibiotics might lead to multiple drug resistances.

“This is an exciting study because it goes beyond what anyone else has done and looks at the whole ecology of the animal’s intestinal tract,” said microbiologist Stuart Levy, director of the Center for Adaptation Genetics and Drug Resistance at Tufts University in Boston.

“This information really takes us a stride forward,” Levy said. “Maybe we don’t need antibiotics. Maybe we could use something else. This could be opening doors to a new way of raising animals.”

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