UT RESEARCH MIGHT HOLD KEY TO BEE DEATHS
Tetracycline kills gut bacteria bees need to stay healthy, study finds.
A common antibiotic appears to be killing helpful bacteria in the guts of honeybees, making it at least partly responsible for the rapid collapse of domestic colonies, according to new University of Texas research.
Bees treated with tetracycline had “dramatically fewer gut microbes,” or bacteria that help them absorb nutrients and block pathogens. The bee stomachs also contained more of a harmful bacterium that appears to have killed them, according to the findings.
Lead researcher Kasie Rayman said the findings, published Tuesday in the academic journal PLOS Biology, are not sweeping enough that beekeepers should abandon antibiotics, which can help colonies survive other health risks. But the research does add to the growing body of evidence that overuse of antibiotics con-
tributes to “honeybee colony collapse.”
The research also suggests that — because the collection of microbes in bee stomachs has a lot in common with the microbes in human intestines — overuse of antibiotics can make people sicker, as well.
“It’s going to be important (as a next step) to understand how exactly the antibiotics changed” the microbes in bee guts, Rayman told the American-Statesman.
Honeybees pollinate a third of the food consumed in the U.S., plus coffee and cotton. But more than half of managed U.S. honeybee colonies have mysteriously disappeared in the past dozen years. Their decline prompted the Obama administration in 2015 to announce an effort to stabilize the population of bees and other pollinators.
Theories abound as to why they are dying off: loss of habitat, increased exposure to pesticides, vulnerability to certain kinds of fungi and parasites. The prevailing theory is that a combination of problems has caused colonies to die off.
Beekeepers typically apply tetracycline to their hives several times a year to prevent “foulbrood,” a bacterial infection that can kill larvae or leave them malformed. Previous research has found antibiotic-resistant bacteria developing in bees, as well as in other animals, such pigs and chickens.
Rayman, a postdoctoral fellow, said she chose to study the effects of tetracycline in part because of the similarity between the community of organisms in a bee’s gut and those in a human’s. A person’s gut is more complex and generally off-limits for the kinds of testing done on animals.
As part of the research, Rayman took collections of bees into a “cold room,” where they would go to sleep. Some bees were fed a sugar solution mixed with tetracycline, and some got just the sugar solution.
Those fed the antibiotic fared worse. Rayman found that the tetracycline “cleared out” the good gut microbes, making way for serratia, a harmful kind of bacteria. The bees treated with tetracycline were only half as likely to survive as those not treated.
Despite the obvious implications, Rayman said she will need more research before knowing whether beekeepers should change their practices. “We didn’t do this study with the aim of making recommendations for beekeeping practices,” she said.
Honeybees pollinate a third of the food consumed in the U.S., plus coffee and cotton. More than half of managed U.S. colonies have disappeared in the past dozen years.