Antimicrobial Coatings to Prevent Biofilm Formation on Medical Devices - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 169

the material from which the medical device was made on the quality of coating
formed by different agents on these devices. Additionally, we review different
in vitro assays, animal models for biofilm development, and clinical trials used to
assess the effectiveness of each agent and the rate of success of each coating based
on these assessments. Finally, we summarize any reported toxicity associated with
these coatings.

1 Introduction

Biofilms are microbially derived sessile communities in which the cells are irre-
versibly attached to a substratum, interface, or to each other (Donlan and Costerton
2002 ). Within the biofilm, bacteria are embedded within an extracellular polysac-
charide matrix (EPS) (Donlan and Costerton 2002 ). The growth as well as the
expression of different bacterial genes within the biofilm is different from those of
their free-living counterpart (Donlan and Costerton 2002 ). Available evidence,
from studies performed on Pseudomonas aeruginosa , suggests that biofilms
develop in four stages: reversible attachment, irreversible attachment, maturation,
and dispersion (Sauer et al. 2002 ). In the reversible attachment, P. aeruginosa
attaches to a substrate using its polar flagellum (Sauer et al. 2002 ). During irre-
versible attachment P. aeruginosa becomes nonmotile, and this transition involves
the development of bacterial clusters (Sauer et al. 2002 ). These bacterial clusters
will develop and their thickness increases during the maturation stage (Sauer
et al. 2002 ). During maturation, pores and channels develop within the biofilm.
During the dispersion stage, some bacteria detach from their biofilm structure.
Within the biofilm, microorganisms are highly resistant to different antimicrobial
agents including antibiotics, germicides, and disinfectants (Sauer et al. 2002 ).
Among the different mechanisms that contribute to their resistance are the ability
of the EPS to reduce the penetration of antimicrobial agents; the alternation in the
growth of microorganisms within the biofilms; and the physiological changes that
are induced by the alternation in the growth mode (Suci et al. 1994 ; Duguid
et al. 1992 ; Desai et al. 1998 ).
Biofilm develops on numerous medical devices causing extensive medical and
economical losses. Among these medical devices are the following: urinary cath-
eters, central venous catheters, prosthetic heart valves, contact lenses (CLs), contact
lens cases, dental unit water lines, and intrauterine devices. Therefore, medical
devices that prevent or significantly reduce biofilm development are urgently
needed. The most successful approach so far has been coating the medical device
surface with antimicrobial agents. In this chapter, we describe different strategies
that were developed to coat these medical devices (urinary catheters, central venous
catheters, contact lenses, and contact lens cases) with different antimicrobial

agents.