MRSA-stomping antibiotic discovered

Hospital superbugs could be defeated by African soil

Doctors may have a powerful new weapon in the battle against deadly drug-resistant bugs. A compound isolated from South African soil samples offers potency against all the big hospital killers.

Research funded by drug giant Merck screened over 250,000 chemicals for antibiotic activity. The international team, reporting in Nature, hit upon a small molecule they called platensimycin, after Streptomyces platensis, the species of soil bacteria that makes it. Some bacteria release their own antibiotics to gain advantage in the competition for resources.

Platensimycin works to kill bacteria in a way unlike any other antibiotic, and is one of only three new classes of the drug discovered since the goldrush of the 40s and 50s.

The new drug exploits a vulnerability in how disease-causing bacteria build the membrane that surrounds their cells. It knocks out a key enzyme in the process. Tests proved its effectiveness against NHS pariah MRSA, which claimed more than 1,000 lives between 2003 and 2004*.

When antibiotics were discovered in the first half of the 20th century, doctors kicked off an evolutionary “arms race” with bacteria. By hitting them with powerful drugs, at first they could kill all, or nearly all, the microbes of an infection.

The key word there is nearly.

The problem for modern wards dealing with the threat from MRSA and other antibiotic “superbugs” is that in some of those early bacterial populations, there were a few individuals that, thanks to genetic quirks, would not be killed.

The strong artificial selection (intentional or unintentional modification of a species through human actions), combined with the bacteria's sheer numbers and super-quick time between generations (as little as 20 minutes in optimum conditions), meant they were quickly able to evolve tricks to cope with increasing doses and novel drug formulae.

Lately, it seemed as though bacteria had gained an unassailable upper hand in the tussle. Many of the big pharma firms have pulled back from antibiotic discovery programmes, apparently having made the call that evolution had made it too difficult to be financially viable. Thousands of drugs don't make it to market and sit, unusable, in company compound archives.

Experts naturally urge caution on platensimycin; it's only been tested in mice so far. It will be several years before it could appear on hospital pharmacy shelves.

The array of clinical compounds currently used are essentially small variations on a few themes, so a totally novel stick to beat the bugs with is important, potentially life-saving news. ®

*1,168, Office of National Statistics.

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