Antibiotic-resistant bacteria are a growing concern in nearly all fields of health study, but recent research from Michigan State University reveals that one of the biggest threats has been sitting right under our noses. According to U.S. News and World Report, the continued use of antibiotics in farm animal feed is a massive contributor to the escalating issue of antibiotic-resistant bacteria.

According to microbiology and molecular genetics professor James Tiedje from Michigan State, “In the fight against the rise of antibiotic resistance, we need to understand that the use of one antibiotic or, in some cases, antibacterial disinfectants may increase the abundance of multi-drug resistant bacteria.”

The study tracked large farms raising pigs in both the United States and China. Researchers found that on farms where antibiotics were used regularly in feed, drug-resistant strains of bacteria were extremely common. Antibiotics are added to animal feed to promote growth and ward off diseases.

To make matters even more complicated, Tiedje said, keeping track of the sources of antibiotic-resistant strains is becoming increasingly difficult due to the widespread use of antibiotics and the ability of bacteria to transfer resistant traits across generations.

The researchers acknowledge the need for antibiotics in large-scale animal farms that provide population centers with a consistent supply of meat. If a disease were to break out on a farm near a city, for instance, a large number of people could get sick. But this problem is not eliminated by antibiotics – they may only be postponing it.

As bacteria face antibiotic treatments, the lucky few individuals that survive rapidly split and multiply, passing on the gene that allowed them to resist the drug in the first place. After all of the weak bacteria are wiped out by an antibiotic, the ones that survived are left over to reproduce and potentially unleash a super-resistant strain that shows little response to antibiotics.

The CDC estimates that at least 2 million Americans become infected with a drug-resistant strain of bacteria, resulting in an estimated 23,000 deaths annually.

A press release from Michigan State University describing the details of the study can be found here.