Have you ever had a bacterial infection like strep throat (Streptococcal pharyngitis)? Then you probably received some kind of an antibiotic from your doctor. They likely told you to take the full course of antibiotics, or all the pills you received. This protects against antibiotic resistance. This is when an antibiotic no longer kills bacteria it once controlled.

Yet prescriptions are not the only source of concern for antibiotic resistance. In fact, over 70 percent of antibiotics sold in the United States are given to livestock, including cattle. This has a significant effect on human health.

How Bacteria Develop Resistance

For much of human history, bacteria have presented a danger to human health with diseases like the bubonic plague (caused by Yersinia pestis) wiping out large parts of the world's population. Fortunately, the development of antibiotics has revolutionized treatments for such bacterial diseases. They have not been able to spread as they once did. Yet this safety is being put at risk by growing antibiotic resistance.

Like other organisms, bacterial populations evolve. When bacteria are exposed to an antibiotic initially, most will die. However, some bacteria can develop a genetic mutation, or change. This change allows them to survive and multiply even after being exposed to an antibiotic.

Some bacteria have already developed antibiotic resistance. Notably the bacteria that cause staph infections, methicillin-resistant Staphylococcus aureus, are highly resistant to antibiotics.

Resistant Bacteria in Cattle

Antibiotics are given to farm animals for some of the same reasons they are given to humans. Livestock are often housed together in close quarters, where there is increased risk for spreading disease. Cattle are also at risk for infections because they are often fed a corn-based diet despite having evolved to eat grass. Antibiotics are often fed to cattle as a preventative measure, rather than as a treatment.

Antibiotics have another unexpected benefit. They allow livestock to grow larger much more quickly than usual. Many cattle producers feed livestock low doses of antibiotics for long periods of time. This gives them a greater profit from a single animal, but it contributes to antibiotic resistance.

Bacteria in Meat and Milk

Antibiotic resistance not only affects cattle's health. It impacts many people as well, because many of the antibiotics given to cattle are also used in human medicine. When a person eats meat or drinks milk from an animal with antibiotic-resistant bacteria, that person may become infected too.

Antibiotic-resistant bacteria can also make their way into the air, water, and soil. For example, manure from cattle is often used to grow vegetables. If this manure contains antibiotic-resistant bacteria, it can spread to vegetables and soil.

Not all bacteria is harmful; some are helpful to people and other animals. The good bacteria in our gut is known as our microbiome. The increased use of antibiotics can also harm our microbiome. This can result in short-term infections and long-term health consequences, such as impaired immunity.

Fighting Antibiotic Resistance

The dangers of antibiotic resistance are recognized all over the world. Governments are responsible for establishing guidelines for antibiotic use in livestock. Partnerships between governments, cattle producers, and veterinarians are aimed at reducing the overall use of antibiotics. This means only using antibiotics prescribed by a veterinarian and not using antibiotics to improve production. Improving livestock care could also help reduce the spread of disease and thus the need for antibiotics.

You can also help prevent the spread of antibiotic resistance by lowering how much meat you eat, which reduces your risk for infection. Consumers can also look for meat labeled "antibiotic free." And finally, don't forget to cook foods to their appropriate temperature, separate meats and vegetables, and wash your hands.

Stopping antibiotic resistance demands the combined efforts of many people. However, like the discovery of antibiotics, the effort to stop antibiotic resistance will transform human and animal health alike.

Antibiotic Resistance Is Beefing Up

As antibiotic-resistant "superbugs" become stronger and more common, studying these organisms, such as this methicillin-resistant variant of Staphylococcus aureus, is becoming increasingly vital to the development of medical treatments.


substance that can stop or slow the growth of certain microbes, such as bacteria. Antibiotics do not stop viruses.

antibiotic resistance

ability of bacteria to become resistant to treatment with antibiotics.

Plural Noun

(singular: bacterium) single-celled organisms found in every ecosystem on Earth.


(deoxyribonucleic acid) molecule in every living organism that contains specific genetic information on that organism.


proteins that accelerate the vital processes in an organism.


change in heritable traits of a population over time.

gut bacteria
Plural Noun

microorganisms that live in the digestive tract of animals. Also called gut flora and gut microbiota.

horizontal gene transfer

transferral of genes between genomes and sometimes between different species.


animals raised for human use.


microorganisms and genetic material present in or on a specific environment.


very infectious, often fatal, disease caused by bacteria.


circular DNA within bacteria.

vertical gene transfer

process by which genes are transferred from parent to offspring.