Bacterial Biofilms: A Slimy Situation For Medical Devices

From the WebMD Archives

March 9, 2000 (Atlanta) -- The very instruments used to keep patients alivecan be a source of deadly infection. Catheters, artificial valves, and othermedical devices are remaining in place longer than ever, and colonization withslimy, tenacious bacterial biofilms is a growing problem, according toresearchers at a CDC conference on hospital infections.

John W. Costerton, PhD, director of Montana State University's Center forBiofilm Engineering, explained that biofilms are groups of bacteria growing information. The cells secrete a slimy material that forms a protective barrieraround the colony. Though biofilms have been studied extensively in industrialsettings, only recently has that knowledge been applied to medicine.

Biofilms, often disgusting but generally benign -- dental plaque and showercurtain mildew are examples -- can pose a serious threat when they form onmedical devices. While a healthy person can safely shower in or even ingestbiofilm, a patient whose urinary catheter or breathing tube is sheddingbacterial colonies is in serious jeopardy, says Costerton.

"The impact of [breathing in] a large lump of bacteria enclosed in aslime matrix is a very serious challenge to health," he says. Animalexperiments show that lungs can deal with a large number of single bacterialcells, 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 theCDC's Hospital Infections Program, it may be easier to prevent biofilms fromforming than to get rid of established colonies, because "they are verytenacious and difficult to remove from a device, even with disinfection."To that end, prevention research is taking several approaches, ranging frommechanical to biochemical. Researchers, for example, are working on smoothersurfaces that discourage bacteria from adhering to them.

Biofilm "is not something new," says Michael Bell, MD, a hospitalepidemiologist who is also with the CDC's Hospital Infections Program."Organisms have been able to do this nifty thing for a very long time, butare now becoming important because we are creating a population of susceptiblepeople [while] increasingly using invasive devices," he says.

Contact lenses and urinary catheters are easily removable sources ofpotential infection related to biofilm, Bell says, but devices such aspacemakers, prosthetic heart valves, and artificial joints pose more difficultchallenges. "Improved medical devices have yielded unexpected consequences.There is a whole array of potential new sites for biofilm." Rather thanlooking for ways to prevent it, however, the best approach might be to delayit. If it's delayed enough, he says, the problem becomes moot.

Research is still "in an early, very exciting phase," says Bell. Fornow, doctors should focus on adhering to proven infection-controlstrategies.


Vital Information:

  • Biofilms are groups of bacteria growing in formation, and they are aproblem because many medical devices provide a suitable environment forcolonization.
  • Catheters, artificial valves, and other devices are remaining in placelonger than ever, and can be a source of serious infections for patients usingthem.
  • Researchers believe that it is probably easier to prevent biofilms byfinding better materials for medical devices than to get rid of establishedcolonies, but research to combat this problem is still in the earlyphases.