May 8, 2012 -- Antibiotics found in river sediment, farmed soil, and other sources are polluting the environment and contributing to the rising rates of antibiotic resistance, a new report suggests.
Antibiotic resistance occurs when a bacteria grows immune to the effect of an antibiotic or class of antibiotics. It has been called one of the world's greatest health threats by the CDC, the FDA, and the World Health Organization.
New research in Environmental Health Perspectives analyzed how antibiotics in the environment affect illness-causing bacteria including E. coli. The researchers found that antibiotic pollution in the environment has led to the proliferation of resistant bacteria.
"This ... reinforces previous studies which highlight that antibiotic contaminants in the environment may be leading to the development of antibiotic resistance," says researcher Alfredo Tello in a news release. He is a PhD student from the University of Stirling's Institute of Aquaculture in Scotland. "Antibiotics are being overused and we're seeing the emergence of resistance to infections that we used to be able to treat."
Their overuse has caused what's called "selective pressure." When exposed to antibiotics, bacteria can either die or survive. Selective pressure occurs when these bacteria survivors replicate and their offspring quickly become the dominant type of bacteria. As a result, an army of hard-to-treat germs can arise and spread to humans.
"This adds more science to the fact that antibiotic resistance doesn't just happen at the animal level," says Gail Hansen, DVM, MPH. She is a senior officer with the Pew Charitable Trusts in Washington, D.C. "It gets get into lagoons or the environment, in general, and has an additive effect on antibiotic resistance."
She adds that "even lower levels of antibiotics can get into the environment and be high enough to cause resistance."
Sometimes, antibiotics are given to food animals to speed growth and compensate for less-than-hygienic conditions. The FDA recently gave the food industry three years to voluntarily stop using antibiotics to make food animals grow faster.
The bottom line? "Antibiotics are having an effect even after they are outside of the animal," Hansen says. "It doesn't stop."
Other Drivers of Antibiotic Resistance Matter, Too
Still, the inappropriate, indiscriminate use of antibiotics by doctors is one of the main drivers of antibiotic resistance, explains Philip M. Tierno Jr., PhD. He is director of clinical microbiology at NYU Langone Medical Center and a clinical professor at the NYU School of Medicine.
How do these antibiotics get into the environment? "Things go down the drain, get flushed or thrown in garbage, and leach into soil," he says. "This is the first study that showed the effect of concentrations of antibiotics in the environment and how this leads to resistant strains of illness-causing bacteria."
The public health consequences are significant. "If a person got one of these bugs and is in the hospital and being treated, the antibiotic therapy may fail and they may succumb to a once-treatable infection," Tierno says. "The handwriting is on the wall, and these studies continue to remind us that we have to do something."
"On an individual level, this means not eating antibiotic-riddled food, not throwing unused antibiotics in the garbage, and not begging your physicians for antibiotics."
Antibiotic resistance is on the rise, agrees David Hirschwerk, MD. He is an attending physician in the division of infectious disease at North Shore University Hospital in Manhasset, N.Y. "More bacteria are becoming resistant to more types of antibiotics," he says.