A biofilm is a microbially derived sessile community characterized by cells that:

are irreversibly attached to a substratum, interface, or to each other are embedded in a matrix of extracellular polymeric substances that they have produced have exhibited an altered phenotype with respect to growth rate and gene transcription(1).

Biofilm formation is a critical factor influencing the contamination of tap water. Biofilms are prone to form on the internal lumens of plumbing systems⁽²⁾, due to the availability of nutrients in the water and other factors such as:

Water chemistry Water flow Water stagnation Water temperature Surface materials of construction Degree of surface corrosion Degree of shear stress over the surface Degree of surface flushing

8.09 MB AVI Movie With kind permission of the Hygienic Institute of Bonn University (Prof. Exner)

Biofilm and Antimicrobial Resistance:
Some biofilm-associated bacteria display a higher level of resistance to antimicrobial agents than planktonic (free-floating) bacteria^(1-3). Their increased level of antimicrobial resistance can be attributed to the failure of the antimicrobial agent to reach target biofilm cells due to its inability to:

• penetrate biofilm’s extracellular polymeric matrix
• penetrate dense cell aggregates and microcolonies
• bind to the extracellular polymeric matrix

Biofilm and Systemic Water Disinfection Methods:
Systemic water treatment methods such as hot water flushing, hyperchlorination, chlorine dioxide, copper-silver ionization, ozonation, ultraviolet light, and monochloramines are generally unable to permanently eradicate biofilms from healthcare facility plumbing systems over the long-term⁽²⁾. These treatment methods do not respond effectively to sudden, unanticipated infusions of hospital water systems with high concentrations of pathogens due to:

• Facility renovation projects
• Municipal water system breakdown and repair activities
• Seasonal water quality variations

The stages of biofilm formation include:

• Surface preconditioning
• Reversible adhesion
• Irreversible adhesion
• Maturation
• Shedding

Biofilm and Point-Of-Use Filtration:

• Point-of-use 0.2 micron filters for water faucets, showers, ice machines, and water sources used for rinsing of medical devices can either provide cost effective insurance against the inadequacies of systemic water treatment methods or replace them entirely.

References:
1. Donlan, R.M. and J. W. Costerton. 2002. Biofilms: survival mechanisms of clinically relevant microorganisms. Clin. Microbiol. Rev. 15(2):167-193.
2. Ortolano, G.A., M.B. McAlister, J.A. Angelbeck, J. Scaffer, R.L. Russell, E. Maynard, and B. Wenz. 2004. Hospital water point-of-use filtration: a complementary strategy to reduce the risk of nosocomial infection. Filtration Supplement 1:3-26.
3. Costerton, J.W. and P.S. Stewart. 2001. Battling biofilms. Scientific American 285(1):74-81.