RODALE NEWS, EMMAUS, PA—Flies can do more than annoy you at a summer picnic. A new study in press at the journal Science and the Total Environment has revealed that they can carry antibiotic-resistant bacteria, increasing our exposure to germs that are hard to kill.
THE DETAILS: Researchers from Johns Hopkins Bloomberg School of Public Health set up traps to collect flies near 8 poultry farms and then collected samples of poultry litter (a mix of manure and bedding materials) from 3 large-scale, conventional poultry operations in that same area. Both the poultry litter and the flies were found to harbor antibiotic-resistant strains of bacteria—“superbugs” that don’t respond to medicines commonly used to treat them. This isn’t the first study linking large-scale farms, often referred to as CAFOs, or "concentrated animal feeding operations," to drug-resistant bacteria. A small study of 20 Iowa hog farms, published in February in the online journal PLoS One, found that nearly 50 percent of the animals carried methicillin-resistant Staphylococcus aureus, or MRSA. That study is in line with others from Canada and Europe that have found similar relationships between MRSA in hog farmers and their animals. MRSA, one of the most widely publicized forms of antibiotic-resistant bacteria, can cause a severe skin infection that does not respond to standard antibiotics and can be fatal.
WHAT IT MEANS: If our farms are harboring MRSA and other medicine-resisting germs, it’s a threat to all of us. There’s potential for the microbes to spread to people who don’t live within a fly’s distance of a poultry farm, or anywhere near a hog farm, says Hopkins study coauthor Ellen Silbergeld, PhD, professor of environmental health sciences and epidemiology at the Johns Hopkins School of Public Health. In fact, a recent Johns Hopkins study found that cars traveling behind poultry-transport trucks were contaminated with drug-resistant bacteria. “This study points to a general breakdown in food safety and oversight of how we grow, produce, ship, and store food that humans consume,” says Silbergeld. Finding the bacteria in flies may be a particularly ominous sign, says Stuart Levy, MD, professor of medicine at Tufts University and author of The Antibiotic Paradox: How the Misuse of Antibiotics Destroys Their Curative Powers. “This just indicates that you have no control over where bacteria will go, ” he says. Fortunately, there’s no evidence of flies directly transmitting resistant bacteria to humans, though research by Dr. Levy and others has found flies to be important vectors for transmitting bacteria between farms.
Here are a few ways to minimize your exposure to antibacterial-resistant germs, and help eliminate them: