Australian Seaweed Compounds Block Drug Resistant Bacteria

SYDNEY, Australia, December 8, 2004 (ENS) - A whole new type of antibiotic medicine may emerge from chemicals discovered in an Australian seaweed, new research suggests. The seaweed appears to be able to sidestep the resistance to antibiotics that is making many species of bacteria hard to kill.

Scientists at the University of New South Wales (UNSW) have found that compounds known as furanones – isolated from the seaweed Delisea pulchra – can prevent the bacteria that cause cholera from switching on their signaling mechanisms. This deadly disease now claims some 5,000 lives each year.

"There is an increasing number of antibiotic resistant bacteria and a decreasing number of drugs in the pipeline," says Dr. Diane McDougald, a senior research associate at the UNSW Centre for Marine Biofouling and Bio-innovation. "We need to find new approaches to treat bacterial infections."

Furanones do not kill bacteria but instead jam their ability to send signals to each other. As a result, they are far less likely to create the drug resistance problems that plague current anti-microbial treatments.

Furanones from Delisea pulchra block disease causing cholera signals. (Photo courtesy )

Furanones may have the same effect on many other bacteria, such as those that cause food poisoning and infections related to cystic fibrosis, the researchers say.

The bacteria that cause golden staph infections and tuberculosis have become resistant to many antibiotics and are becoming harder and harder to treat, but they may yield to furanones, the scientists believe.

"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," McDougald said.

The team has found that when the bacteria that cause cholera, Vibrio cholerae, are exposed to furanones, they cannot switch on their so-called virulence factors associated with infection and the development of the disease.

"The new experiments suggest that furanones may prevent cholera bacteria from escaping the host immune response and secreting toxins to weaken their host," says 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 behavior and attach themselves to a surface on a host or in the environment.

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.

"This is very exciting as these are the first antimicrobials of their type that have been shown to be effective," said UNSW professors Staffan Kjelleberg and Professor Peter Steinberg, who are on the research team.

Kjelleberg and Steinberg discovered furanones' ability to interfere with bacterial signaling systems in the 1990s. Synthetic versions of these compounds have since been made.

In 1999 a separate company Biosignal Ltd was established to act as a vehicle for commercialization of selected "smart molecules," including furanones, identified in the research activities of the UNSW Centre for Marine Biofouling and Bioinnovation.

Professor Steinberg is on Biosignal’s Board of Directors and both he and Professor Kjelleberg are shareholders in the company, which is publicly listed on the Australian Stock Exchange.

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

The number of officially reported cholera cases worldwide varies between 110,000 and 200,000 cases a year, causing an average of 5,000 deaths, but the World Health Organization believes the true number is probably higher.