Bacterial Slime Clogs Cystic Fibrosis Lungs

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Cystic fibrosis (CF) is one of the most common fatal genetic diseases in the United States. Approximately 30,000 Americans have the disease and an estimated 8 million are carriers of it. (1) Thick, sticky mucus clogs the lungs and intestines of those with CF, causing malnutrition, frequent lung infections, breathing difficulty, and eventually permanent lung damage. Bacteria, especially Pseudomonas aeruginosa, thrive in this thick mucus, causing persistent infection. Most people with CF die from respiratory failure caused by these infections--often around the age of 30.

Once these bacteria gain a foothold in CF lungs, they are invincible even to long-term antibiotic treatment. Scientists led by Dr. E. Peter Greenberg of the University of Iowa College of Medicine revealed why. (2) The researchers showed that the bacteria encase themselves in a protective slime called a biofilm. Partial to wet surfaces, biofilms are responsible for everything from dental plaque and bathtub soap scum to bacterial colonies that corrode the bottom of ships. Within gluey pockets in the biofilm, colonies of bacteria flourish, nourished by a network of water-filled channels and shielded from the effects of antibiotics. Dr. Greenberg and his coworkers developed a sensitive lab test that detects biofilms in CF lungs, based on telltale molecules produced by the structures.

This technique could form the basis for a diagnostic test to detect the presence of biofilms in a wide range of medical conditions and industrial processes. The work might also help scientists design drugs to prevent biofilms from forming or to disrupt them after they have become established.

Biofilm Image

Biofilms, like this laboratory-grown specimen, form fortress-like structures that protect the bacteria from antibiotics and from the immune system of infected hosts. Because of this, biofilms are extremely difficult to treat and often persist indefinitely.


1 Cystic Fibrosis Research Directions, National Institute of Diabetes and Digestive and Kidney Diseases, NIH Publication No. 97-4200, July 1997.

2 Singh PK, Schaefer AL, Parsek MR, Moninger TO, Welsh MJ, Greenberg EP. Quorum-sensing signals indicate that cystic fibrosis lungs are infected with bacterial biofilms. Nature 407: 762-4, 2000.

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