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The new adventures of old antibiotics

By | April 25, 2011, 11:10 AM PDT

Reuse your… antibiotics? Canadian scientists are breathing new life into existing infection fighters.

Resistance to many of these currently available drugs, they say, is a ubiquitous and relentless clinical problem compounded by a dearth of new therapeutic agents.

But by combining them with other drugs – nonantibiotic drugs – the researchers have identified new ways to kill unwanted microbes, offering “an opportunity to sample a previously untapped expanse of bioactive chemical space,” the authors write.

The team, led by Eric Brown and Gerard Wright of McMaster University, tested combinations of antibiotics with known drugs used to treat Parkinson’s disease, cancer, and inflammatory diseases.

For decades, obvious efforts to combine antibiotics to increase their efficacy against resistant bacteria don’t go far enough, says Wright. Only considering other antibiotics is too limiting: “You need to cast the net a bit wider and look at other molecules that are bioactive.”

  • They identified several cases where a nonantibiotic drug weakens bacterial cells, making the bacteria vulnerable to the proven antibiotics.

Focusing on minocycline (pictured) – an antibiotic frequently used in the 1950s and 60s until bacteria developed resistance – they screened it in combination with more than 1,000 previously approved bioactive drug compounds.

The Scientist explains the unexpected interactions:

The screen revealed a total of 69 compounds never before used to treat bacterial infections that, when combined with minocycline, decreased bacterial growth by at least 45% – significantly more than when treated with only the antibiotic.

“These combinations might be a way to selectively target bacteria and combat disease and leave so-called ‘good bacteria’ intact to do other things,” Wright says. “In effect you use fewer antibiotics to get the same effect.”

In one creative combination, the over-the-counter loperamide – sold as Imodium to treat diarrhea – can make bacterial cells sensitive to a variety of antibiotics like minocycline. This could one day help patients with cystic fibrosis, the world’s most common hereditary lung disease.

“Previous advances in treating cystic fibrosis have been in managing infection,” says Brown, “but since infectious organisms are increasingly developing resistance to antibiotics, the importance of providing new treatments is more important than ever.”

It typically takes 13 to 15 years to develop a drug, but according to Brown, this approach could cut drug development time in half.

The study was published in Nature Chemical Biology yesterday.

Image: PubChem

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Janet Fang

About Janet Fang

Janet Fang is a contributing editor for SmartPlanet.

Janet Fang

Janet Fang
Contributing Editor

Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York.

Follow her on Twitter.

Janet Fang

Janet Fang

Janet does not have financial holdings that would influence how or what she covers.

She writes for SmartPlanet and is not an employee of CBS.

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Has MRSA Tested?
A good test would be to use this combo on MRSA that has a high tolerance for antibiotics. Also, what are the side effects with combining an antibiotic with another bioreactive chemical?

One of the factors that make a resistant bacterial strain is not taking the full course of antibiotics or taking antibiotics for viruses. The clinics and doctors should stop prescribing antibiotics for virus problems and educate people to use up the antibiotics prescribed.
Posted by sboverie
26th Apr 2011
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