Antibiotic-resistant bacteria from cattle feed yards can become airborne, according to a study to be published in Environmental Health Perspectives this month.
Researchers from Texas Tech University collected particle matter samples downwind and upwind of 10 large-scale cattle feed yards within a 200-mile radius of Lubbock, Texas, over six months. The researchers found bacteria containing antibiotic-resistant genes were 4,000 percent more prevalent in the samples collected downwind from the feedlots than in the samples collected upwind. The Texas Tribune described the study area, in the Texas Panhandle, as "one of the most windswept stretches of the country" and "home to a high concentration of industrial cattle feedlots."
"Finding out where these particles are traveling and how far is an important question," study co-author Phil Smith said. "Specifically these gene sequences: What happens when they land? These are tremendously important questions and ones that we are interested in answering."
This is not the first time antibiotic-resistant 'superbugs' have become airborne. A 2012 study found that sneezing, coughing and shaking bedclothes in hospitals can propel superbugs into the air, allowing them to travel on air currents and potentially infect other hospital patients. The Texas study, however, is the first to examine airborne transport of antibiotic-resistant bacteria from feed yards.
While it's difficult to say if this specific strain of bacteria will affect the nearby community, it certainly wouldn't be impossible: The notorious MRSA outbreak, which killed more than 18,000 people in the United States in 2005, is one example of a pathogen that first became antibiotic resistant in livestock, but affected human health.
Antibiotic-resistant bacteria limit doctors’ ability to treat life-threatening bacterial infections and account for at least 2 million illnesses and 23,000 deaths each year, according to the Centers for Disease Control and Prevention. In January, the White House announced that it was increasing funding to fight antibiotic resistance, including measures like educating health care providers to stop prescribing unnecessary antibiotics to patients. Still, the fact remains that 80 percent of the antibiotics sold in the U.S. aren't directly used by humans -- they are used on livestock.
Antibiotics prescribed to cattle are not only used to treat disease, but also as a growth promoter. Cows can’t easily absorb the antibiotics, so they are passed back into the environment (along with 'super bacteria' not killed by the antibiotics) when the cows expel waste, and are released into the air when the fecal material from the cow pen floor dries out.
Researchers have long known that antibiotic-resistant bacteria from livestock fecal matter could be transmitted to humans through manure used on agricultural farms and contaminated runoff water, but this is the first study to indicate that the antibiotic-resistant particles could become airborne and ingested by humans who come in contact with them. The researchers estimate that the antibiotic-resistant bacteria could remain active for days or weeks after being deposited on skin, soil or water and could spread far past the borders of the feed yards by blowing dust, a common weather pattern in the Southern high plains, and one that could become even more common with global warming.
Still, co-author Greg Mayer cautioned that the study isn't meant to be alarmist. "If you think about it, every time you take a trip to the hospital you have a great risk of breathing in, touching or ingesting antibiotic-resistant bacteria -- but the steps from there that lead to an infection are multifold. Our own immune systems take care of most of that on a daily basis or we'd be sick all the time," Mayer said. "We just want to make sure we don't deplete our first line of defense against bacterial diseases."