Antibiotics may help animals spread salmonella

Giving animals antibiotics may make them sicker and could lead some to spread even more salmonella than they would have otherwise, U.S. researchers experimenting on mice said. The findings in the Proceedings of the National Academy of Sciences could point to a new concern over feeding healthy livestock low doses of antibiotics to help them grow and stave off common illnesses, a practice that critics say may fuel drug-resistant superbugs. Researchers at Stanford University School of Medicine gave oral antibiotics to mice infected with Salmonella typhimurium, a bacteria which can cause food poisoning. A small minority, known as “superspreaders” because they had been shedding high amounts of salmonella in their feces for weeks, remained healthy. It appears neither the antibiotic or the illness had much effect on them.

The rest of the mice got sicker instead of better and, oddly, started shedding like superspreaders.

A statement from Stanford University School of Medicine

A previous Stanford study found that giving non-superspreader mice an oral antibiotic led to a rapid increase in salmonella shed in their feces. This study showed that giving streptomycin, an antibiotic, to salmonella-infected mice, led most of them to begin shedding high levels of the pathogen in both their gut and their feces. Most of the treated mice also appeared sicker after the antibiotics.

We need to think about the possibility that we’re not only selecting for antibiotic-resistant microbes, but also impairing the health of our livestock and increasing the spread of contagious pathogens among them and us.

Denise Monack, associate professor of microbiology and immunology

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