Adhesion of bacteria to surfaces and biofilm formation on medical devices
K.A. Floyd, A.R. Eberly, M. Hadjifrangiskou
Vanderbilt University Medical Center, Nashville, TN, United States
For some time after their discovery, bacteria were believed to exist as free-floating (planktonic), unicellular organisms. This paradigm began to shift in the early 1930s, when Dr. Arthur Henrici noted that bacteria isolated from aquatic environments appeared to accumulate and grow on submerged surfaces (Henrici, 1933). This observation was confirmed in 1940 by Drs. H. Heukelekian and A. Heller, who observed that surfaces allowed for bacterial growth in solutions too dilute of nutrients to normally sustain their growth. Despite the growing knowledge that bacteria exist in nonfree-floating forms, the term biofilm was not coined until 1975 when Mack et al. used it for the first time to describe bacterial communities. Since that initial observation, great strides have been made to better understand the multicellular bacterial communities known as biofilms. “Building upon early observations, research” has begun to elucidate the stages guiding biofilm formation, the different strategies employed by different species/strains to build biofilms, the characteristics of the biofilm community as a whole, and the behavior and interactions of bacteria within these bustling “bacterial cities.” The communal lifestyle afforded to biofilm bacteria offers many advantages including protection from harsh environmental conditions and stressors, enhanced genetic exchange via horizontal gene transfer, and the chance for mutualis- tic or symbiotic relationships with other bacterial species.
When biofilms form within a vertebrate or invertebrate host, they can impart beneficial or detrimental effects. Because the biofilm lifestyle offers protection to the bacterial community from outside stressors, formation of biofilm within a host protects the resident bacteria from the impact of the immune response, as well as molecules with antimicrobial properties. To date, biofilm-associated infections account for most hospital-acquired infections and present a significant risk to the world’s population (Hidron et al., 2008; Hall-Stoodley et al., 2004). In order to develop new methods to target and treat biofilm-associated infections, it is imperative to first have a clear understanding of the underlying bacterial mechanisms that govern the complex process of biofilm formation. The initial attachment of bacteria to a surface is perhaps the most critical step for the establishment of biofilm-associated infection. This chapter describes mechanisms that facilitate contact between bacteria with a surface, as well as the types and regulation of adhesive organelles bacteria use for attachment.
Biofilms and Implantable Medical Devices. http://dx.doi.org/10.1016/B978-0-08-100382-4.00003-4
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The processes that follow initial attachment and lead to the formation of a biofilm are then described, followed by what is currently known regarding biofilm dispersal mechanisms. The information in this chapter is largely derived from studies using single-species biofilms, but many of the concepts also apply for polymicrobial biofilms, which are covered briefly in Section 3.7.