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Biofilms are resistant to antiseptics and antibiotics for a number of reasons.
"During our medical training, we look at slides of individual or clumped microbes," Dr. Eaglstein says. "But bacteria more often exist in colonies with fungi, yeast and viruses, surrounded by an extracellular matrix. Channels in the matrix deliver fluids and take away wastes. The microorganisms communicate by quorum sensing signals."
What is a biofilm?
Biofilms are produced by staphylococcus strains isolated from impetigo and furuncle and have been viewed via confocal laser scanning of bullous impetigo lesions, atopic dermatitis and pemphigus folliaceous. They have been implicated as a factor in the resistance to the treatment of dermatophytoma and in the pathogenesis of acne vulgaris.
"I believe we will find that the microorganisms in biofilms are playing a role in many diseases, especially chronic diseases like acne vulgaris that can be more persistent in one area, like the chin, than others. The patient is likely to have a biofilm in the resistant area," Dr. Eaglstein says.
History of biofilmsIn 1943 Claude Zobell noted that marine bacteria prefered to colonize surfaces. These colonies were later discovered in a wide range of environments, but the word "biofilm" wasn't coined until 1973.
In the medical realm, biofilms have been linked to a wide range of diseases and account for the vast majority of chronic infections within the body, such as infections linked to implants and lung and inner ear infections. More recently, they have been associated with slow-healing or healing-resistant wounds.
"There are probably good and bad bacterial biofilms," Dr. Eaglstein says, "but no one knows much about them yet."
Previous experiencePreviously, while associated with the dermatology department at the University of Miami, Dr. Eaglstein was involved in several biofilm studies.
One, which was led by Anna Falabella, M.D., identified biofilms in chronic wounds. Another involved making wounds on pigs. Planktonic bacteria were then recovered using a flush technique and biofilm bacteria, by scrubbing.
"Counts went down after treatment with chlorhexidine, but the biofilm bacteria were much more resistant," Dr. Eaglstein reports.
Strategies for disrupting biofilmsBiofilms are resistant to antiseptics and antibiotics for a number of reasons.
The exo-polysaccharide matrix forms a boundary. Outer flanks of bacteria offer protection to those on the interior. The colonies can slow their metabolism, form new metabolic pathways, and pump antibiotics out of the matrix. Furthermore, the interior of the matrix contains antibiotic degrading enzymes.
Scientists are considering different ways of disrupting biofilms, mostly by breaking down the extracellular matrix, so antibiotics have a better chance of killing bacteria.
Photoenergy has been used to disrupt dental plagues, and pulsed ultrasound has been proven to aid aminoglycoside antibiotics in killing Escherichia coliin vivo. Also under study is the possibility of enhancing lactoferrin, a component of the body's innate immune response, as well as combination doses of antibiotics and enzymes.
Finally, Dr Eaglstein mentioned a more theoretical approach: disruption of quorum sensing molecules.
"There are probably many other ways too," he says. "One approach may work in one situation but not in another."
Future research needs to identify the most effective strategies for disrupting biofilms, correlate results from in vitro and in vivo studies, and ascertain the difference between normal flora and probiotics, Dr. Eaglstein says.