MSU Slimy Bacteria Study Appears in Major Journal

       MSU scientists Betsey Pitts and Phil Stewart are coauthors on a paper on bacterial resistance to antibiotics published in the Nov. 20 issue of the prestigious journal Nature.

Antibiotics don't work against bacteria stuck together in tight-knit communities called biofilms. That much scientists knew.        But just why biofilm bacteria act that way whereas other bacteria do not has puzzled researchers for years and made the control of biofilm infections much more difficult.
Now scientists at Montana State University-Bozeman and two other universities believe they have part of the answer: genetics. Bacteria turn on different genes when they form biofilms, and one characteristic of that particular genetic expression is a resistance to antibiotics.        The researchers' findings appear in the Nov. 20 issue of the prestigious journal Nature.       "One of the most vexing problems in biofilms is that when microbes band together in a biofilm they are remarkably protected from killing by antibiotics, biocides and disinfectants," said Phil Stewart, deputy director of the Center for Biofilm Engineering at MSU-Bozeman and study co-author. "And of course we'd like an explanation for that."       For years scientists intuitively thought that the bacterial clusters created a physical barrier that prohibited the antibiotics from getting through.  But in a project led by researchers George O'Toole
	MSU scientists Betsey Pitts and Phil Stewart MSU photo by Stephen Hunt

and Thien-Fah Mah at Dartmouth Medical School, the scientists showed that the antibiotics do penetrate the biofilm. But they don't kill the bacteria.
      The scientists worked with Pseudomonas aeruginosa, a biofilm-forming bacterium that's one of the biggest troublemakers in cystic fibrosis lung infections, burn wound infections and infections associated with the use of catheters. It and other biofilm bacteria can become from 10 to 1,000 times more resistant to antibiotics than non biofilm bacteria.
      The scientists traced this resistance to one gene--called ndvB--that switches on in a biofilm and protects the bacteria from dying. It's likely that ndvB isn't the only gene involved, Stewart said, but its discovery tells scientists that additional genetic studies of biofilm bacteria may yield even more surprises.
      “This is the first time anyone has used an unbiased genetic approach to understand why biofilms are resistant to antibiotics,” said lead author Mah, a postdoctoral fellow at Dartmouth Medical School.
      Biofilms are thought to cause up to 65 percent of human bacterial infections, according to the Centers for Disease Control and Prevention. The communities form on medical implants, teeth (plaque), internal organs and in the middle ear where they cause childhood ear infections. Biofilms also can form in industrial settings such as oil pipelines and in municipal water plants and pipes. 
      Now scientists can envision drugs that potentially interfere with the expression of specific genes in bacteria or with the proteins those genes make as a way of treating biofilm infections.
      "A gene is a very powerful, concrete handhold on a problem, and this is one of the first examples of biofilm protection occurring at the genetic level," Stewart said.  
      The Nature study also involved MSU research scientist Betsey Pitts and two biologists from MIT. Funding came from a variety of federal agencies, including the National Science Foundation through its long-term support of the MSU Center for Biofilm Engineering, the world's largest group devoted to biofilm research, Stewart said.   

Contact: Dr. Phil Stewart
phil_s@erc.montana.edu
406 994-2890
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