Lab-dish tests in Switzerland have raised hopes that a soil bacterium identified nearly 60 years ago could be a "very selective killer" of the germ that causes tuberculosis, a European journal reported on Monday.

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Pyridomycin, a natural antibiotic exuded by the bacterium Streptomyces pyridomyceticus, shows promise as a candidate to fight a drug-resistant strain of TB, researchers in Switzerland said.

According to the UN's World Health Organisation (WHO) at least half a million of the eight to nine million people who each year develop TB have a
strain that is resistant to frontline drugs.

Pyridomcycin works by inhibiting a single gene called InHA which, in mutant strains, helps the TB microbe thwart isoniazid drugs.

Germs that were exposed to pyridomycin became depleted in fatty acids, which were essential to building the bacterial cell wall.

"Nature's antibiotic, pyridomycin, is a very selective killer of Mycobacterium tuberculosis, the bacterium responsible for tuberculosis in humans," said Stewart Cole, a professor at the Federal Polytechnic School of Lausance (EPFL) in Swizerland.

"It is also active against mycobacteria that have developed resistance to front-line drug treatments such as isoniazid."

The research appears in EMBO Molecular Medicine, published by the European Molecular Biology Organisation (EMBO).

Japanense scientists in 1953 were the first to see pyridomycin as a potential agent against TB bacteria. There was a bout of interest in 1986, but
further development has been limited because how it worked was unclear.