Wednesday, May 17, 2006


WEDNESDAY, May 17 (HealthDay News) -- Researchers report that they've unearthed a new antibiotic that might become a potent weapon against two dangerous germs that are bedeviling hospitals.

The antibiotic, discovered in South African soil, hasn't been tested in humans and is years away from showing up on pharmacy shelves. Still, the researchers said it has plenty of potential, especially since no other similar drugs have landed on the market since 2000.

At issue are several bacteria that have developed resistance against existing antibiotics, and are starting to creep into the community. One is a staph infection known as methicillin-resistant Staphylococcus aureus (MRSA), which can cause pneumonia in hospital settings and skin infections in the general population. Another is vancomycin-resistant Enterococcus(VRE).

"It's just an inevitable process that eventually all these bacteria will be resistant to the compounds we have now," said study author Stephen Soisson, a senior scientist at Merck Research Laboratories. "It's a looming global health crisis."

In their search for a new antibiotic, Soisson and his colleagues looked at 250,000 extracts from natural products, including samples of soil and leaf debris from around the world. They think they may have found what they're looking for in a soil sample from South Africa.

The researchers tested an antibiotic derived from a substance found in the soil. They report their findings in the May 18 issue of Nature.In mice, the antibiotic, known as platensimycin, vanquished both MRSA and VRE. Apparently, the antibiotic works by disrupting the way cells synthesize crucial fatty acids.

Frank Myers, a clinical infectious disease epidemiologist at Scripps Mercy Hospital in San Diego, said the findings about platensimycin are "very encouraging," and the drug could become another treatment option for doctors, especially those treating patients who develop MRSA-related pneumonia in hospitals. Those cases, he said, are especially hard to treat.

However, there are caveats, Myers added. Infectious disease specialists will want to know if the germs develop resistance to the new antibiotic and whether it kills healthy bacteria and contributes to a diarrheal illness.Also, he said, doctors may be cautious about using platensimycin except in the most dire cases, to avoid creating antibiotic resistance.

Yahoo News


New Antibiotic Aimed at Resistant Germs

May 17, 2006 05:01:19 PM PST

Scientists have found a chemical that might one day prove critical in the ongoing fight against germs that have developed resistance to existing antibiotics.

The compound, discovered by researchers from the pharmaceutical firm Merck & Co., could herald the first major new class of antibiotics in decades. It has already proven effective in curing mice infected with antibiotic-resistant bacteria.

That doesn't mean it will work in people, but outside experts are impressed with the results, which are reported in this week's issue of the journal Nature.

The researchers found the compound in a scoop of soil from South Africa. They named it platensimycin, because it is produced by the soil bacterium Streptomyces platensis as a weapon in its own battles against other microbes.

"We need to continuously find antibiotics," said Sheo Singh, Merck's director of natural products chemistry.

With the recent emergence of "superbugs" that are resistant to even the most potent antibiotics, there is a real possibility that in the near future some infections will simply be incurable.

Part of the problem is that most antibiotics are just modifications of drugs that have been around for half a century. In addition, despite all the recent advances in genetics and molecular biology, the hunt for new antibiotics is still conducted by trial and error.

The Merck researchers addressed both problems with a clever genetic trick that made an existing drug-hunting process more effective and also targeted novel types of antibiotics.

Their innovation was to test extracts of fungi, plants and other natural substances against bacteria with a genetically engineered Achilles' heel. Because the bacteria were weakened, any compound that harmed them would have a more dramatic effect and thus be easier to identify.

The Merck scientists also chose the genetic handicap carefully, placing it in a metabolic pathway that is not attacked by any major existing antibiotics. That increased the likelihood that any promising compound they discovered would be something for which the bacteria had not yet developed a resistance.

"We screened over 250,000 extracts that came from things isolated all the way around the world," said Merck scientist Stephen M. Soisson.

One of them, platensimycin, showed exceptional promise in vitro. It also proved highly effective when tested in mice infected with a common and troublesome strain of Staphylococcus aureus.

"I'm guessing that this is a very promising molecule," said Eric D. Brown, a biochemist at McMaster University in Hamilton, Ontario.

He noted that the majority of potential antibiotics never reach the pharmacy even after proving effective in mice. But by publishing a report about platensimycin in one of the world's most influential journals, Merck is signaling an unusual level of confidence in the compound's prospects.

"I think it's probably going somewhere," Brown said.

If so, it would be a bright spot for the besieged New Jersey pharmaceutical company, which is fending off thousands of lawsuits over its painkiller Vioxx, pulled off the market in 2004.

Of course, even if platensimycin turns out to be a clinically useful antibiotic, bacteria will inevitably become resistant to it just as they have existing drugs.