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Editor's Note: Tables and figures referenced below can be found as a slideshow here.
This year marks the anniversary of the birth of Charles Darwin 200 years ago and his heralded work, Origin of Species, 150 years ago. The concept of "I" and individual selection in his work was a central theme, so this is an interesting time to discuss biofilms.
Biofilms are, in fact, at the opposite end of the spectrum. They favor the expressions of Elle Metchnikoff and Peter Kroptokin who, in the mid 1800s, described the microbial benefits of "we." It is the classic confrontation of competition ("I") versus cooperation ("we"), and in celebration of Charles Darwin, it is remarkable that the emergence of biofilms as a significant contributor in medical illnesses so focuses on the community and the concept that the total benefit of cooperation is greater than the individual participants.
Biofilms and the Healthcare Team
Slide 7 in the related slideshow highlights the impact of biofilms on the complete medical/dental/administrator healthcare team. This is an attempt to unmask and highlight the central theme that biofilms now have in infectious processes, both in the hospital and out, and the magnitude or consequence of traditional diseases. It applies to the physician, pharmacist, microbiologist, infection control nurse and, of course, the administrator. All have unique roles within patient-care management, but unless all five recognize the importance of biofilms and their associated consequences, we will continue to have a problem.
Consequences
Given the opportunity, 99.9 percent of organisms would rather attach (sessile) than be free-floating (planktonic). Another interesting corollary: Louis Pasteur and Robert Koch talked about transmission in disease production associated with one organism ("I"). Here, we can describe the consequences of biofilms as anti-Koch and anti-Pasteur in that the organism pool is multiple species organized in an intact 3-D structure with an extracellular polymeric backbone; it has features more often associated with a hydrated polymer and materials rather than microbiology.
Slide 1 outlines the devices now used in medicine and dentistry to highlight the advantage of bacteria attaching versus free-floating. The estimated numbers per year with published infections, risks or colonization, is shown. The diversity of indwelling medical devices is remarkable (IMD) and will only expand given the population dynamics in the U.S. and the use of indwelling medical devices in an aging population.
Initially, five diseases were recognized as biofilm associated. They were recognized in the dental community first as caries and periodontitis associated, but recently expanded to include significant medical diseases-otitis media, cystic fibrosis, respiratory infections, sinusitis and others.
Two of the most recent biofilm-associated infections (BAI) are ventilator-associated pneumonia (VAP) and chronic wounds. In the former, greater than 50 percent of the ICU resources may be utilized attending to the patient with VAP and the number of inpatients and outpatients with chronic wounds/ This is growing at a significant rate and includes pressure (Decubitus) ulcers, diabetic foot ulcers and venous leg ulcers.
Slide 2 highlights the common indwelling medical devices grouped by inpatient versus outpatient and is an attempt to unmask the importance of biofilms and biofilm-associated infections, not only in the hospital environment but in the outpatient and clinic environment where people have considerably less information about handling, cleaning and maintaining devices with biofilms attached.
Biofilms Defined
Biofilms are microbially derived sessile communities characterized by cells irreversibly attached to a substratum or to each other (Slide 3). The organisms are embedded in a matrix of extracellular polymeric substances they produce and exhibit an altered phenotype with respect to growth rate in gene transcription. Biofilms, in fact, act like materials, not microbes. They act as a hydrated polymer exhibiting physical characteristics best described by viscoelasticity and rheology. Those are terms well described by engineers, which is appropriate given that engineers were the first in the late 1900s to recognize the importance of biofilms in altering the consequence of filtration devices and heating exchange devices air conditioning and water cooling towers.
Slide 8 highlights the interface of the three primary characteristics of a biofilm and underlines its uniqueness based on the members within the community. The characteristics of the biofilm are highlighted in Slide 9. A number of investigators have described the unique organization and repetitive biofilm structures throughout the universe as an "intellectual design," but the primary biologic consequence is the concept of "competition" versus "cooperation" (Slide 4 ). This is the major reason that bacteria living together as a community are able to survive and become the preeminent force within microbial diseases and the producers of retractable or nontreatable infections.
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