Biomedical Implications of the Porosity of Microbial Biofilms - Porous Media: Applications in Biological Systems and Biotechnology - page 122

4.3.4 Antimicrobial Resistance in Infectious

Bacterial Biofilms ................................................... 134

4.3.5 Porosity and Diffusional Limitations in Biofilms ................... 137

4.4 Infectious Microbial Biofilms—Treatment

Modalities and Resistance .................................................. 142
4.4.1 Antibacterial and Antifungal Treatment Modalities

of Infectious Biofilms................................................ 142

4.4.2 The Impact of Porosity and Diffusional Limitations

on Treatment Ecacy .............................................. 145

4.5 Concluding Remarks ........................................................ 149

4.6 References ................................................................... 150

4.1 Introduction
Biofilms are mostly considered as a slimy layer of microorganisms adher-
ing to solid surface (de Beer and Stoodley 2006). The earliest phase of
studying biofilms was focused on the physical properties of the solid sur-
face, for example, roughness, hydrophobicity, and hydrophilicity. As electron
microscopy developed, a more detailed picture of the structure of microbial
biofilms emerged. The subsequent development of confocal scanning laser
microscopy, coupled with fluorescent markers, allowed visualization of live
hydrated biofilms as three-dimensional architecture (Costerton et al. 1995).

4.1.1 What Is a Biofilm?
Biofilms may be broadly defined as communities of microbial cells associ-
ated with a surface, typically encased in an extracellular matrix (Ghan-
noum and O'Toole 2004). This definition is applicable to biofilms formed on
solid-liquid interfaces as well as on semisolid-air interfaces and relates to a
wide range of surfaces, including steel pipes, soils, medical implants, bioma-
terials, tissues, and epithelial cells. The most abundant biofilms ( > 90% of
microorganisms) are associated with environmental biofilms found in nature
or throughout biotechnological applications (Lens et al. 2003; Tandoi et al.
2006). Studies of these biofilms were dominated by phenotypic behavior, for
example, biofilm life cycle and resistance to antibiotics (O'Toole et al. 2000b;
Chandra et al. 2001; Reysenbach and Shock 2002). Ongoing research in the
field aims at understanding the community physiology, metabolism, ecology,
structure/function relationships, and the role of gene exchange, with the over-
all objective of providing a database for the development of ecient strategies
to control biofilm development and methods to eradicate them. The number
of studies directed toward better understanding of the physical characteristics
of biofilm, for example, porosity and three-dimensional structures of biofilms
is substantially low.