Weeding Out Bacteria

Australian seaweed may hold the key to slowing down drug-resistant bacteria, which have increasingly frustrated the medical profession.

Slimy plant life floating around the ocean may hold the key to slowing down the spread of certain infections, and could lead to a new strain of drugs that won't be susceptible to antibiotic resistance, a problem the Centers for Disease Control calls one of its top concerns.

University of New South Wales researchers found that seaweed compounds, called furanones, can stop the bacteria that cause cholera by cutting off the communication systems enabling the disease to spread. The breakthrough has researchers speculating that furanones will likely also work against other bacteria, including those that cause staph infection, food poisoning and tuberculosis -- which are increasingly becoming resistant to some antibiotics.

According to the CDC, every year nearly two million people in the United States get infections in the hospital, and 90,000 die. And 70 percent of the bacteria that cause these infections are resistant to at least one antibiotic.

But researchers say bacteria won't have an incentive to develop mutations that will foil furanones because they dont actually kill bacteria, only block their communication with each other, which prevents them from growing strong enough to cause problems.

"The fact that the furanones do not kill the cells means that there is no disadvantage to the individual cell, but only to the (bacteria) community as a whole,"says Dr. Diane McDougald, a senior research associate at the University of New South Wales Centre for Marine Biofouling and Bio-innovation. "So the (selective) pressure to develop resistance is very low or not at all."

Many bacteria rely on quorum sensing -- a communication system that determines when enough bacteria is present to overwhelm the hosts immune system. The Australian seaweed, a red algal species found in Sydney's Botany Bay, prevents bacteria from sensing a quorum, thereby stopping the formation of biofilms on leaves. That's significant because in people, biofilms can cause resistant, chronic infections.

"It's one of the better studies documenting the effects of a marine natural product on marine bacteria,"says Paul Jensen, an assistant research microbiologist at the Scripps Institution of Oceanography in La Jolla, California. "The testing of these compounds as antibiotics is a logical extension of this work."

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Some researchers believe bacteria might eventually outsmart any obstacle thrown their way, including compounds derived from furanones. If bacteria can detect an advantage, they might mutate in a way that allows them to circumvent the furanone signal jamming.

"(The furanone approach) depends on the assumption that there is truly no selective advantage of quorum-sensing proficiency in life and growth of the organisms,"says Susan Rosenberg, professor of molecular and human genetics and molecular virology and microbiology at Baylor University in Houston. "This might be so. But if there is a growth advantage for those capable of quorum sensing, then mutants that defy the blocker will be selected."