Crab Compound Acts as Weapon Against Bacterial Biofilm Infections

Laboratory studies at Montana State University find that a chemical compound found in crab and shrimp shells known as chitosan can help prevent infectious bacteria from sticking to wound dressings, catheters and other medical devices.

Philip Stewart, who directs the University's Center for Biofilm Engineering says chitosan can stop nasty microbes on contact. "It makes it hard for a cell to do anything active, and probably discourages the bacteria from setting up shop on that surface."

Once these sticky layers of bacteria, or biofilms, 'set up shop' and take hold, they are difficult to treat and often require removing the device or surgical implant. Biofilms account for up to 65 percent of the bacterial infections in the United States, according to the Centers for Disease Control and Prevention.

Stewart says laboratory tests of bacteria growth showed dramatic results when chitosan was used. "When we do this on a surface that doesn't have chitosan we get about a million bacteria per square centimeter on that coating after two days of challenge. When we put the chitosan coating on and put it into the system and let it run for two days, we end up with around 10,000 times less bacteria on that surface."

Stewart says scientists were unable to detect any viable organism in five of the nine experiments using chitosan. He says, despite such results, it is unlikely that any single technology could defeat biofilms, but suggests that chitosan is a likely platform from which to launch further experimentation.

"We can load a conventional antibiotic [to the chitosan], or one of these agents that block the communication between bacteria that seem to be important in virulence and biofilm formation. So I think that combined strategies may be what really ends up working in the clinical setting."

Steward presented his work in San Francisco at the 232nd national meeting of the American Chemical Society, the world's largest scientific society.