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Image of seaweed Delisea pulchra
Photo: Rob Harcourt
© Rob Harcourt

Chemical compounds known as furanones isolated from the seaweed Delisea pulchra hold great promise for tackling bacterial diseases, researchers at the University of New South Wales believe. The seaweed, a red algal species found at a UNSW marine research site in Sydney's Botany Bay, produces the compounds to prevent bacteria from forming biofilms on its leaves.

Furanones do not kill such microbes but simply "jam" their ability to send signals to each other. In turn, that means the bacteria are unable to determine when enough of them are present in the immediate area - a phenomenon known as "quorum sensing" - to launch a concerted attack on their host .

The UNSW scientists have found strong evidence, for example, that furanones can stop the bacteria that cause cholera from switching on their disease-causing mechanisms.

It seems likely that furanones can have the same effect on many other bacteria, such as those that cause food poisoning and cystic fibrosis-related infections.

This means as well that their use is far less likely to create the drug-resistance problems that plague current anti-microbial treatments.

"This is very exciting as these are the first antimicrobials of their type that have been shown to be effective," says Dr Diane McDougald, a Senior Research Associate at the UNSW Centre for Marine Biofouling and Bio-innovation. Dr McDougald is conducting the research in association with UNSW's Professor Staffan Kjelleberg and Professor Peter Steinberg.

"The fact that furanones prevent bacterial communication means that they may be effective against a wide range of bacteria that have communication systems, such as the bacteria that cause golden Staph infections and tuberculosis," she says.

"These bacteria have become resistant to many antibiotics and are becoming harder and harder to treat. Because furanones don't kill the bacteria, there is no selection pressure for them to develop resistance. Indeed, in a million years of evolution, no natural resistance has been developed by bacteria to these furanones in the natural environment.

"Our experiments suggest that furanones may prevent cholera bacteria from escaping the host immune response and secreting toxins to weaken their host," says Dr McDougald. Many bacteria rely on a signaling system known as quorum sensing to detect when enough of their own kind is present and then change their behaviour and attach themselves to a surface on a host or in the environment.

The discovery - so far only established in laboratory tests -- is now being tested further in trials involving mice and tissue cultures.

"There is an increasing number of antibiotic resistant bacteria and a decreasing number of drugs in the pipeline," Dr McDougald says. "Thus, we need to find new approaches to treat bacterial infections. The furanone compounds are especially exciting as they do not kill the bacteria, but just stop them from expressing disease-causing traits. This means that there is no pressure on the bacteria to develop resistance."