Antibiotic resistance genes in our food?
May 25,2007 00:00 by Bend_Weekly_News_Sources

The food we eat could be promot­ing the dis­turb­ing spread of an­ti­bi­ot­ic-re­sist­ant in­fec­tions, sci­en­tists warn.

Harm­less bac­te­ria in our food car­ry genes that pro­vide re­sist­ance to an­ti­bi­otics, the re­search­ers ex­plained. Once in our bod­ies, they might trans­mit these genes to di­s­ease-caus­ing bac­te­ria, mak­ing them more dan­ger­ous.

“The mag­ni­tude of an­ti­bi­ot­ic-re­sist­ant bac­te­ri­al con­tamina­t­ion in the food chain is tremen­dous,” said Hua Wang of Ohio State Un­ivers­ity in Co­lum­bus, Ohio, who pre­s­ents the find­ings May 23 at the Amer­i­can So­ci­e­ty for Mi­cro­bi­ol­o­gy an­nu­al meet­ing in To­ron­to. 

Still Life With Food by Jan Da­v­idsz de Heem (1626-1683)

“Food could be an im­por­tant av­e­nue for an­ti­bi­ot­ic-re­sist­ant bac­te­ri­al ev­o­lu­tion and dis­semina­t­ion.”

An­ti­bi­ot­ic-re­sist­ant in­fec­tions arise when bac­te­ria evolve de­fenses against the an­ti­bi­otics with which hu­mans have been at­tack­ing them for years. Of­ten, the mi­crobes need­n’t evolve re­sist­ance on their own: they can get the re­sis­tance genes free from their neigh­bors.

The cul­prit, Wang said, is a pro­cess known as hor­i­zon­tal gene trans­fer, in which bac­te­ria near each oth­er can share ge­net­ic in­forma­t­ion. Gene trans­fer among di­s­ease-caus­ing bac­te­ria in hos­pi­tals is al­ready a rec­og­nized prob­lem. Re­search al­so shows that di­s­ease-caus­ing bac­te­ria can get genes from harm­less mi­crobes, in­clud­ing those in food, Wang said. Par­tic­u­larly wor­ri­some, she added, is that these or­gan­isms are plen­ti­ful and have a rich gene pools, and some are par­tic­u­larly ef­fi­cient at shar­ing genes.

Hua and col­leagues tested var­i­ous ready-to-eat foods in­clud­ing sea­food, meats, dairy, deli items and fresh pro­duce from gro­cery chain stores. Re­sist­ance gene-car­ry­ing bac­te­ria turned up through­out the sam­ples, ex­cept in pro­cessed cheese and yo­gurt, she said.

An­ti­bi­ot­ic-re­sist­ant in­fec­tions are a grow­ing pub­lic health prob­lem, said Mar­i­lyn Roberts of the Un­ivers­ity of Wash­ing­ton in Se­at­tle: de­pend­ing on the case, an an­ti­bi­ot­ic-re­sist­ant in­fec­tion could tri­ple a hos­pi­tal stay. A me­thi­cil­lin-re­sist­ant Staph­y­lo­coc­cus au­re­us in­fec­tion can cost thou­sands of dol­lars more to treat. In some cases, such as the new ex­ten­sively re­sist­ant tu­ber­cu­los­is, an­ti­bi­otics no long­er work, forc­ing doc­tors to take ex­treme meas­ures like re­mov­ing an in­fected lung.

The prob­lem is­n’t con­fined to the food sup­ply, Hua said: re­cent stud­ies have found re­sist­ance genes in bac­te­ria in ba­bies’ di­ges­tive tracts. Since these chil­dren had­n’t eat­en sol­id food yet, they must have ac­quired these genes some­where oth­er than the food sup­ply, sug­gest­ing re­sist­ance genes from the en­vi­ron­ment were in­volved, said Hua.

“An­ti­bi­otics and the con­tamina­t­ion of the en­vi­ron­ment is a med­i­cal prob­lem, an ag­ri­cul­tur­al prob­lem and a hu­man prob­lem. Eve­ry­body plays a role,” Roberts said. But there are things that can be done to min­i­mize con­tamina­t­ion in our food, Hua added. “Given the prop­er in­vest­ment of mon­ey, ef­fort and time we can iden­ti­fy the steps that need to be tak­en at the pro­cess­ing level.”

Courtesy American Society for Microbiology and World Science staff