Bacteria from the U8 tributary on the Savannah River Site were found to be resistant to antibiotics.

Antibiotic resistance is on the rise in an alarming amount of bacteria, but overuse and misuse of antibiotics may not be the only cause.

Ecologists have recently found that in polluted areas, more bacteria have developed antibiotic resistance. The role of environmental contaminants in the amount of resistance seen today could help explain how antibiotic resistance is so widespread.

Antibiotics are our main line of defense against bacterial infection. However, bacteria are highly adaptable and are able to develop resistance to the drugs over time. The more widespread these resistant strains are, the less equipped we are to fight them.

J. Vaun McArthur, a senior research ecologist with the Savannah River Ecology Laboratory and Odum School of Ecology, believes environmental contaminants may be partly to blame for the rise in bacterial resistance. He tested this hypothesis in streams on the U.S. Department of Energy’s Savannah River Site.

The 310-square-mile site near Aiken, South Carolina, was closed to the public in the 1950s, before antibiotics were used in medicine and agriculture. The site was used to produce materials used in nuclear weapons, causing certain areas of the site to be contaminated. Since the streams have not had input from residential and agricultural wastewater, the observed patterns must result from something other than antibiotics.

In one screening, McArthur and his colleagues focused on three streams at the site. Two streams had a long history of waste inputs, while one did not. They found that the two streams with the highest levels of contaminants also had the highest levels of bacteria with antibiotic resistance in both water and sediment samples. With no other source of antibiotic input, the only explanation for the resistance seen in these streams are the waste contaminants.

More than 95 percent of the bacteria samples were resistant to 10 or more of the 23 antibiotics the researchers screened for. These included front-line antibiotics such as gatifloxacin and ciprofloxacin, used to treat basic bacterial infections such as pink eye and sinus infections. McArthur’s study was published in the journal Environmental Microbiology.

The antibiotic-resistant streams feed into the Savannah River, a body of water that is close to to residential communities and ultimately feeds into the Atlantic Ocean.