Thursday, September 09, 2010

"altruistic" antibiotic resistance...,

WorldScience | Confronting at­tack by an­ti­bi­otics, some bac­te­ria help each oth­er out—and un­for­tu­nately for us, they’re bet­ter off for it, re­search­ers have found.

Though a small frac­tion of pathogens in a col­o­ny may have evolved the abil­ity to re­sist a drug or class of drugs, these “su­per bugs” were found to help their more vul­ner­a­ble peers by over-pro­duc­ing a drug-fighting sub­stance.

Pre­vail­ing wis­dom held that an­ti­bi­ot­ic re­sistance works only on an in­di­vid­ual lev­el: a bac­te­ri­um ac­quires a muta­t­ion that con­fers pro­tec­tion against a drug, al­low­ing it to sur­vive and re­pro­duce. Even­tu­al­ly, as vul­ner­a­ble bac­te­ria die, the mu­tan­t's stronger prog­e­ny re­pop­u­late the col­o­ny. This basically reflects how evolution is believed to work in all species: mem­bers that are “fit­ter” or bet­ter adapt­ed to pre­vail­ing con­di­tions spread their genes through the po­pu­lation at the ex­pense of other mem­bers.

But the new stu­dy, to ap­pear in the Sept. 2 is­sue of the re­search jour­nal Na­ture, in­di­cates there are al­so popula­t­ion-wide changes in the bac­te­ri­al com­mun­ity at work. Faced with an on­slaught of an­ti­bi­otics, re­sistant Esch­e­rich­i­chia coli mi­crobes pro­duce—at an en­er­gy cost to them­selves—a pro­tein mol­e­cule that seeps in­to the com­munal broth and trig­gers a slew of pro­tec­tive mech­a­nisms in their non-re­sistant neigh­bors.

The study comes from re­search­ers at the How­ard Hughes Med­i­cal In­sti­tute in Chevy Chase, Md.