March 9, 2000 (Atlanta) -- The very instruments used to keep patients alive can be a source of deadly infection. Catheters, artificial valves, and other medical devices are remaining in place longer than ever, and colonization with slimy, tenacious bacterial biofilms is a growing problem, according to researchers at a CDC conference on hospital infections.
John W. Costerton, PhD, director of Montana State University's Center for Biofilm Engineering, explained that biofilms are groups of bacteria growing in formation. The cells secrete a slimy material that forms a protective barrier around the colony. Though biofilms have been studied extensively in industrial settings, only recently has that knowledge been applied to medicine.
Biofilms, often disgusting but generally benign -- dental plaque and shower curtain mildew are examples -- can pose a serious threat when they form on medical devices. While a healthy person can safely shower in or even ingest biofilm, a patient whose urinary catheter or breathing tube is shedding bacterial colonies is in serious jeopardy, says Costerton.
"The impact of [breathing in] a large lump of bacteria enclosed in a slime matrix is a very serious challenge to health," he says. Animal experiments show that lungs can deal with a large number of single bacterial cells, which are easily destroyed by the immune system, Costerton says, "but a lump of biofilm always produces infection."
According to presenter Rodney M. Donlan, PhD, a microbiologist with the CDC's Hospital Infections Program, it may be easier to prevent biofilms from forming than to get rid of established colonies, because "they are very tenacious and difficult to remove from a device, even with disinfection." To that end, prevention research is taking several approaches, ranging from mechanical to biochemical. Researchers, for example, are working on smoother surfaces that discourage bacteria from adhering to them.
Biofilm "is not something new," says Michael Bell, MD, a hospital epidemiologist who is also with the CDC's Hospital Infections Program. "Organisms have been able to do this nifty thing for a very long time, but are now becoming important because we are creating a population of susceptible people [while] increasingly using invasive devices," he says.
Contact lenses and urinary catheters are easily removable sources of potential infection related to biofilm, Bell says, but devices such as pacemakers, prosthetic heart valves, and artificial joints pose more difficult challenges. "Improved medical devices have yielded unexpected consequences. There is a whole array of potential new sites for biofilm." Rather than looking for ways to prevent it, however, the best approach might be to delay it. If it's delayed enough, he says, the problem becomes moot.
Research is still "in an early, very exciting phase," says Bell. For now, doctors should focus on adhering to proven infection-control strategies.
- Biofilms are groups of bacteria growing in formation, and they are a problem because many medical devices provide a suitable environment for colonization.
- Catheters, artificial valves, and other devices are remaining in place longer than ever, and can be a source of serious infections for patients using them.
- Researchers believe that it is probably easier to prevent biofilms by finding better materials for medical devices than to get rid of established colonies, but research to combat this problem is still in the early phases.