Is Cow Manure Another Reason Why Our Antibiotics aren’t Working?
Groundbreaking research by U.S. scientists has found antibiotic resistant genes in cow manure. Could this be contributing to our rising resistance to antibiotics?
For a long time now, scientists have been aware of a number of antibiotic resistant genes. While usually benign, these genes could become a problem if they were ever to be adopted by bacteria that cause hospital infections, leading to superbugs that normal antibiotics can’t treat and, as a result, possibly life-threatening consequences.
Now Yale University researchers have identified 80 unique antibiotic resistant genes after testing dairy cow manure, and about three quarters of those genes weren’t previously known to science. This matters because dairy cow manure is often used as fertilizer in food growing, and so there is a real chance that those genes could reach bacteria, which create food-borne illnesses.
The study, which is published this month in mBio or the online open-access journal of the American Society for Microbiology, saw researchers use a sequencing technique to identify the genes. The researchers found that three quarters of the genes were only distantly related to genes that had already been identified, while they were also able to identify an entirely new gene family. The latter gene group would potentially create a resistance to a family of antibiotics known as chloramphenicol. This is an antibiotic that is often given to cattle in order to treat respiratory infections. When the researchers then exposed a laboratory strain of E.coli to the genes, they found that the E.coli then became resistant to the antibiotic.
Concerns have previously been raised about the use of antibiotics in agriculture and the impact and how they may increase drug resistance. Due in part to the incredibly poor welfare standards in which poultry are kept, it tends to be poultry that are fed an abundance of antibiotics to fight off disease, and food watchdogs have for a long time now said that this kind of practice will have consequences for human health. Indeed, there is some evidence to support that antibiotics in our food have already contributed to antibiotic resistance, along with an overuse of antibiotics to treat human health problems. This new research points out that farming practices surrounding livestock may also be cause for concern.
The fact that the genes hadn’t before been identified is actually a good thing, though. It means that, at least for now, they’re unlikely to be a threat to our health as they aren’t yet infiltrating the food chain in a meaningful way. However, the researchers believe that there is a chance that cow manure may harbor “an unprecedented reservoir” of antibiotic resistant genes. Obviously, this could pose a significant worry if we want to ensure that our existing antibiotics continue working until we come up with new solutions to the problem of pathogenic bacteria.
The researchers, therefore, will be carrying out a series of studies to try to pinpoint whether these genes are infiltrating our foodchain and at what point.
“The diversity of genes we found is remarkable in itself considering the small set of five manure samples,” researcher Jo Handelsman is quoted as saying. “This is just the first in a sequence of studies — starting in the barn, moving to the soil and food on the table and then ending up in the clinic — to find out whether these genes have the potential to move in that direction. We’re hoping this study will open up a larger field of surveillance, to start looking at new types of resistance before they show up in the clinic.”
There are a number of ways science is looking at tackling the problem of antibiotic resistance. They include limiting antibiotic use and creating entirely new kinds of antibiotics. In the meantime, however, limiting the use of antibiotics in agriculture will be vital and, while the farming industry has appeared to largely ignore calls for greater action, this is a problem that evidently isn’t going away.
Photo credit: Thinkstock.