A small black mushroom found in the woods of northern Europe contains what may be the first of a powerful new class of antibiotics as effective as penicillin.

The compound was isolated by scientists at the Danish biotechnology company Novozymes, reported the health portal MedPage Today.

Plectasin, a peptide derived from a fungus called Pseudoplectania nigrella, is as effective as penicillin and vancomycin in combating experimental peritonitis and pneumonia in mice, it said.

The peptide is one of a class of molecules called defensins, which have previously been found in plants and animals. Plectasin is the first to be isolated from a fungus, Michael Zasloff of Georgetown University Medical Centre said.

Plectasin was tested against a range of bacteria, including streptococcus, enterococcus and staphylococcus, Zasloff said, but other defensins have been shown to have activity against viruses.

Since about 200,000 other species of fungus exist, he said, it seems likely that many more fungal defensins will be found, possibly allowing for highly targeted antimicrobial drugs that will render today's broad spectrum drugs obsolete.

The compound showed no evidence of toxicity in mice, Zasloff said, although further study will be needed to see if it is safe to use in humans. It is very likely, however, that the efficacy seen in mice will translate to people, he said, since the bacterial targets would be the same.

Plectasin is excreted without change in the urine of mice, Zasloff said, a sign that it is safe to use and effective.

The discovery of the compound could not have taken place using conventional techniques, in which the fungi would be grown in liquid cultures and then tested to see if they had any antimicrobial activity.

"When this mushroom is grown in the lab, it doesn't produce much plectasin," he said.

Instead, researchers at Novozymes went "scouring through the genetic messages" of wild fungi, looking for genes that would code for secreted molecules, he said. "One of them coded for what we could clearly see was a defensin," he added.