Bacterial Adhesion: Seen Any Good Biofilms Lately?

Abstract

The process of surface adhesion and biofilm development is a survival strategy employed by virtually all bacteria and refined over millions of years. This process is designed to anchor microorganisms in a nutritionally advantageous environment and to permit their escape to greener pastures when essential growth factors have been exhausted. Bacterial attachment to a surface can be divided into several distinct phases, including primary and reversible adhesion, secondary and irreversible adhesion, and biofilm formation. Each of these phases is ultimately controlled by the expression of one or more gene products. Ultrastructurally, the mature bacterial biofilm resembles an underwater coral reef containing pyramidal or mushroom-shaped microcolonies of organisms embedded within an extracellular glycocalyx, with channels and cavities to allow the exchange of nutrients and waste. The biofilm protects its inhabitants from predators, dehydration, biocides, and other environmental extremes while regulating population growth and diversity through primitive cell signals. From a physiological standpoint, surface-bound bacteria behave quite differently from their planktonic counterparts. Recognizing that bacteria naturally occur as surface-bound and often polymicrobic communities, the practice of performing antimicrobial susceptibility tests using pure cultures and in a planktonic growth mode should be questioned. That this model does not reflect conditions found in nature might help explain the difficulties encountered in the management and treatment of biomedical implant infections

Wound conditioning by vacuum assisted closure (V.A.C.) in postoperative infections after dorsal spine surgery

“…In an experimental study, the rate of infection for steel plates was significantly higher than that for titanium plates [2]. The bacteria within matrix-enclosed communities (biofilm) are protected against host defence and antibiotics, and clinical experience has shown that they must be removed and compromised tissue must be debrided before the infection can be resolved [10,16]. According to the above mentioned procedures of infected implants, their metallic composition and the known effect of the biofilm, in our clinic, usually remove or exchange the implants by one or two stage procedures.…”

The role of cell-surface interactions in bacterial initial adhesion and consequent biofilm formation on nanofiltration/reverse osmosis membranes

“…The repulsive or attractive forces consist of Lifshifz-van der Waals attractive forces, electrostatic repulsive forces and acid base forces. As an oversimplified rule of thumb, primary adhesion between bacteria and abiotic surfaces is generally mediated by nonspecific interactions [14]. Only when the cell and surface are in close proximity do short-range interactions become significant (including hydrogen bonding as well as hydrophobic interactions).…”

“…[14]. At the conclusion of the second stage, adhesion becomes irreversible in the absence of physical or chemical intervention, and the organism becomes firmly attached to the surface.…”

Differential Binding of Escherichia coli O157:H7 to Alfalfa, Human Epithelial Cells, and Plastic Is Mediated by a Variety of Surface Structures

“…The second stage of adhesion employs molecularly mediated binding between specific adhesins and the surface. Once bacteria have irreversibly attached to a surface, the process of biofilm maturation begins (16). Since very little is known about the role of specific surface structures or regulatory proteins during binding of E. coli O157:H7 to food products, we tested whether a collection of E. coli O157:H7 strains carrying mutations in genes encoding proteins associated with binding to tissue culture cells also participate in the association with fresh produce.…”

“…In its most basic form, bacterial adhesion can be divided into the following two stages: the primary or docking stage and the secondary or locking phase (16). Primary adhesion results from a serendipitous meeting between a conditioned surface and a planktonic microorganism.…”