A pill to kill

Teixobactin, the first an­tibi­otic an­nounced in decades, suc­cess­fully treats mice in­fected with su­per­bug Sta­phy­lo­coc­cusaureus

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First an­tibi­otic in 27 years can kill su­per­bug

caus­ing skin and lung in­fec­tions

Thas not seen a new class of HE WORLD an­tibi­otics in the past 27 years. And bac­te­ria are in­creas­ingly be­com­ing re­sis­tant to the ex­ist­ing group of an­tibi­otics. Now a group of Bos­ton-based re­searchers claim to have fi­nally dis­cov­ered a new drug, which they call teixobactin. Bet­ter still, the tech­nol­ogy de­vel­oped by th­ese re­searchers could pave the way for the dis­cov­ery of many new classes of an­tibi­otics.

Mi­cro­bi­ol­o­gists de­velop an­tibi­otics by study­ing the mol­e­cules that soil mi­crobes nat­u­rally make to fend off their com­peti­tors. The trou­ble, how­ever, is that only about one per cent of the mi­crobes can be re­li­ably grown un­der lab con­di­tions. This means sci­en­tists, so far, have not been able to study the re­main­ing 99 per cent.

The team of sci­en­tists, led by Kim Lewis from North­east­ern Uni­ver­sity in Bos­ton, Mas­sachusetts, has in­vented a de­vice that can suc­cess­fully grow un­cul­tured mi­crobes in labs. iChip is a sim­ple de­vice with 96 cham­bers that are used to iso­late and grow bac­te­ria. “We had a sense that we are not smart enough to grow th­ese bac­te­ria in lab set­tings, so we de­cided to grow them in nat­u­ral set­tings,” Lewis said.

The team first di­luted the soil to iso­late a sin­gle bac­te­rial cell from it. Then the cell was in­serted in one of the cham­bers and the de­vice was placed back in the soil so that the cell re­ceived nu­tri­ents and grew nat­u­rally. Af­ter a while, the cham­ber had a colony of bac­te­rial cells that were stud­ied in the lab.The re­searchers claim that gen­er­ally one per cent of mi­crobes in a soil sam­ple are able to grow in the lab, but iChip ex­pands this to 50 per cent. The find­ing was pub­lished in Na­ture on Jan­uary 7,2015.

From soil to pills

With the help of iChip, the re­searchers tested al­most 10,000 bac­te­ria to find mol­e­cules that can limit the growth of su­per­bug Sta­phy­lo­coc­cus aureus, which is fre­quently

found in the hu­man re­s­pi­ra­tory tract and on the skin.

They found 25 po­ten­tial an­tibi­otics, of which teixobactin was the most im­por­tant. The new an­tibi­otic killed the bac­te­ria by pre­vent­ing them from build­ing their outer coats. And more im­por­tantly, when the re­searchers tried to de­lib­er­ately evolve strains of bac­te­ria that re­sist the drug, they failed.The re­searchers used the an­tibi­otic to suc­cess­fully treat mice in­fected with Sta­phy­lo­coc­cus aureus, which causes skin, blood and lung in­fec­tion. The an­tibi­otic also suc­cess­fully killed strains of bac­te­ria that causes tu­ber­cu­lo­sis.

The new an­tibi­otic at­tacks only gram­pos­i­tive bac­te­ria, which have a thick cell wall but lack an outer mem­brane and cause dis­eases such as diph­the­ria and tetanus. Gram-neg­a­tive bac­te­ria are fur­ther pro­tected by an outer mem­brane and this makes them in­sen­si­tive to the an­tibi­otic.

Mile­stone dis­cov­ery

The last an­tibi­otic was found in 1987. In­dis­crim­i­nate use of an­tibi­otics has caused bac­te­ria re­sis­tance, which has been a big con­cern for mi­cro­bi­ol­o­gists world over. Alexander Flem­ing, who dis­cov­ered the first an­tibi­otic, peni­cillin, in 1928 had warned against drug re­sis­tance.

The dis­cov­ery has spe­cial im­por­tance for In­dia and other de­vel­op­ing coun­tries that are worst hit by su­per­bugs. The World Health Or­ga­ni­za­tion has high­lighted that 50 per cent of the to­tal drug-re­sis­tant cases of tu­ber­cu­lo­sis live in In­dia, China and Rus­sia. A re­search done by Ti­mothy Walsh, a med­i­cal mi­cro­bi­ol­o­gist at Cardiff Uni­ver­sity, UK, has found that more than 95 per cent of adults in In­dia and Pak­istan have bac­te­ria that are re­sis­tant to ß-lac­tam an­tibi­otics, which is the most ef­fec­tive an­tibi­otic avail­able to­day. The team says it will take at least a few more years be­fore the an­tibi­otic can be tested on hu­mans.

Pray­toosh Shukla, gen­eral sec­re­tary of the As­so­ci­a­tion of Mi­cro­bi­ol­o­gist of In­dia, says teixobactin an­tibi­otic will play a great role in find­ing so­lu­tions to dis­eases which are drug-re­sis­tant such as tu­ber­cu­lo­sis and blood in­fec­tion. He says the method is sim­ple and can be used by re­searchers glob­ally to find out more an­tibi­otics.

McMaster Uni­ver­sity pro­fes­sor Ger­ard Wright, in a sep­a­rate pa­per pub­lished in Na­ture, says that while it re­mains to be seen whether other mech­a­nisms for re­sis­tance against teixobactin ex­ist in the en­vi­ron­ment, the team’s work could lead to iden­ti­fy­ing other an­tibi­otics that will be more re­silient to bac­te­ria.

The ini­tial re­sults of iChip are def­i­nitely promis­ing. But there needs to be a lot more re­search to en­sure that it de­liv­ers.

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