Scientists say bacteria from soil in South Africa make a potent antibiotic that destroys some of the most dangerous superbugs – ones that kill 8,000 people each year in Canadian hospitals alone.

The antibiotic was used on mice and successfully fought the superbugs – methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) – according to Jun Wang of Merck Research Laboratories in New Jersey and his colleagues.

MRSA, VRE and other bacteria that are resistant to commonly used antibiotics infect another 250,000 Canadians a year and cost the country's health-care systems at least $100 million annually, according to a CBC News investigation in 2005.

It's thought that part of the problem of drug resistance is that most antibiotics work in a similar way, which makes it easier for microbes to quickly adapt and fight back.

In the past 40 years, only two new classes of antibiotics that work in different ways have reached the clinic.

Platensimycin, the newly discovered antibiotic, also has a new mode of action, Wang's team says in a study published in Thursday's issue of the journal Nature.

It blocks enzymes that bacteria use to make fatty acids – the building blocks of cell membranes and bacterial surfaces.

The researchers found it as they screened 250,000 extracts from microbes that produce antibiotics, says their study.

"Wang and colleagues' report of a compound representing a novel class of antibiotic with activity against Gram-positive bacterial pathogens is thus particularly exciting," said Eric Brown, a biochemistry professor at McMaster University in Hamilton, Ont.

Brown, who was writing in a commentary accompanying the study in Nature, said it was an "added bonus" that platensimycin was effective against superbugs.

The researchers showed that platensimycin fights bacterial infection in mice without apparent side-effects.

It would need to undergo extensive tests to show it works and is safe to use in humans.

Nevertheless, Brown called the findings "encouraging."

He also noted that it was heartening to hear that the discovery was made by workers at Merck, given that pharmaceutical companies have generally shifted their focus away from searching for new antibiotics in favour of work on chronic diseases.