Originally created 04/10/98

Study: Bacteria 'slime colonies' can be controlled

WASHINGTON -- Drug-resistant bacteria that kill sick people by building slime colonies in their bodies or in medical equipment may be controlled with chemicals that block the way microbes "talk" to each other, researchers say.

Some of the most common and deadly bacteria do their mischief by forming a sticky scum called biofilm. Individually, the microbes are easy to control, but when they organize themselves into biofilms they can become deadly, said Dr. Barbara Iglewski of the University of Rochester.

"Bacteria love to stick and once they settle down and make a biofilm, it's notoriously difficult to get rid of them," said Iglewski, the co-author of a study to be published Friday in the journal Science.

Biofilms are actually intricately organized colonies of billions of microbes, all working in a coordinated way to defend against attack and to pump out a toxin that can be deadly.

Once they are organized, the bacteria are highly resistant to antibiotics and even strong detergents often cannot wash them away or kill them.

Iglewski and colleagues from Montana State University and the University of Iowa report in Science that they discovered how the microbes in the colonies communicate and found that once this conversation is interrupted, the deadly bugs can be easily washed away.

Using Pseudomonas Aeruginosa, a common bacteria that is a major infection hazard in hospitals and among cystic fibrosis patients, the researchers isolated a gene that the bacteria uses to make a communications molecule. The molecule helps the microbes organize themselves into a biofilm -- a complex structure that includes tubes to carry in nutrients and carry out wastes, including deadly toxins.

In their study, the researchers showed that if the gene that makes the communications molecule was blocked, the Pseudomonas Aeruginosa could form only wimpy, unorganized colonies that could be washed away with just a soap that has no effect on a healthy colony.

"This is basic research, but it leads us into two research directions," said Dr. E. Peter Greenberg of the University of Iowa in Iowa City. "It may help find a way to remove the biofilm or to make it weaker and more responsive to antibiotics."

In a Science evaluation of the work, Dr. Roberto Kolter and Dr. Richard Losick of Harvard University said the new study is an important discovery of "a key step in the normal formation of biofilms."

Pseudomonas Aeruginosa is a major killer of the weak and sick in hospitals. The bacteria coats catheters, tubes and implants, causing major infections. In cystic fibrosis patients, the bacteria set up biofilm colonies in the lungs, causing progressive damage and eventually death.

Greenberg said the bug is an opportunistic bacteria that preys mostly on the weak and sickly who have poor immune systems.

Iglewski said bacterial biofilms also can invade artificial joints, heart valves, pacemakers and even contact lenses.

"When they form in a hot tub, chlorine won't even touch them," she said. "Biofilms are also a major problem in industry since they form virtually anywhere liquids are processed, such as in the food industry."

By disrupting the signals that the bug needs to form its colonies, however, said Iglewski, it may be possible to control the bacteria.

"If you can't destroy the organism, it may be enough to just disrupt its organization," said Greenberg.

He emphasized that will take a great deal more research before chemicals or drugs can be found to control the biofilm.

Science, which published the study, is the journal of the American Association for the Advancement of Science.


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