Current and Emergent Control Strategies for Medical Biofilms - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 112

of biofilm inhibition/disruption by manipulating small molecules. The present
chapter is focused on describing the clinical aspects of biofilm formation and
deleterious effects associated with their presence. This chapter will highlight
current and emergent control strategies for biofilms.

1 Introduction

While microbes are often thought to be multiplying and growing as free floating
cells, most microbes live in aggregations and form complex structures termed
biofilms. These organized structures are communities of microorganisms that
form on solid or liquid interfaces and provide protection to individual cells by
producing extracellular polymeric substances (EPS). The cells in the biofilms
exhibit an altered phenotype compared with corresponding planktonic cells, espe-
cially in regard to gene transcription, and in interacting with each other (Donlan
2002 ; Hall-Stoodley et al. 2004 ). Biofilms result from a natural tendency of
microbes to attach to biotic or abiotic surfaces. The formation of biofilms starts
by irreversible attachment of microorganisms to a surface, which can vary from
mineral surfaces and mammalian tissues to synthetic polymers and indwelling
medical devices, followed by the production of extracellular substances by one or
more of the attached microorganisms (Nikolaev and Plankunov 2007 ; Dongari-
Bagtzoglou 2008 ).
Typically, most of the research on infectious microorganisms is conducted on
single-celled (planktonic forms) of bacteria and fungi because of ease of study and
manipulation. Consequently, most of the drugs developed have efficacy against
planktonic forms of microbes, and unfortunately these drugs do not work or work
poorly against the same organisms in their biofilm form. Moreover, the failure of
antibacterial and antifungal drugs to combat such infections is due to the increased
resistance and/or tolerance of the organisms in their biofilm state. The National
Institute of Health estimates that biofilms cause more than 80 % of infections,
which have imposed an enormous cost on human health (Sachachter 2003 ). Most
infections on biomedical devices and mucosal surfaces, including oral and
uro-genital tracts, are reportedly caused by the biofilm growth of Escherichia
coli , Pseudomonas aeruginosa , Staphylococcus aureus , Streptococcus pyrogens ,
and Candida albicans (Donlan 2001 ; Wilson 2001 ; Douglas 2002 ).
Development of effective strategies to control or prevent biofilm-associated
infections requires a thorough understanding of the biofilm development process
(Jain et al. 2007 ). The adhesion of bacteria to a surface depends on a number of
microbiological, physical, chemical, and material-related parameters. Biofilms may
consist of mono or mixed species, are highly interactive, and employ a range of
cell-to-cell communication or “quorum sensing” (QS) systems (Hogan 2006 ;
Jayaraman and Wood 2008 ). This phenomenon for promoting collective behavior
within a population is important for ensuring survival and propagation by enhanc-
ing access to nutrients and niches, as well as for providing protection (Nikolaev and