Tetra­cy­cline kills gut bac­te­ria bees need to stay healthy, study finds.

Austin American-Statesman - - FRONT PAGE - By Marty Toohey mtoohey@states­man.com

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.

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