Current and Emergent Control Strategies for Medical Biofilms - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 113

Plankunov 2007 ). The dense population structure in biofilms also increases the
opportunity of gene transfer between the species which can convert a previously
avirulent commensal organism into a highly virulent pathogen (Molin and Tolker-
Nielson 2003 ). The enhanced efficiency of gene transfer in biofilms induces
enhanced stabilization of the biofilm structure but, more importantly, also facili-
tates the spread of antibiotic resistance (Molin and Tolker-Nielson 2003 ; Wuertz
and Hausner 2004 ). The increasing emergence of drug resistance to commonly used
antibiotics and antifungals has increased the need for the identification of novel
therapeutics and approaches. Therefore, understanding how antibiotic resistance
develops is a prerequisite to the design of intervention strategies intended to
minimize the threat of biofilm-associated infections. This chapter outlines our
understanding and current state of knowledge of the nature of microbial biofilms
in clinical context with emphasis on novel prophylactic and therapeutic strategies
targeting prevention and management of biofilms.
2 Clinical Significance of Biofilms
It is estimated that the majority of clinical infections exist as biofilms rather than as
planktonic cells. In medical settings, biofilms can occur in several places, such as
the intestinal brush border (e.g., Vibrio cholerae ), urethral lining (e.g., Neisseria
gonorrhoeae ), lymphoid patches in the intestine (e.g., Salmonella typhimurium )
(Costerton et al. 1999 ), antibiotic-recalcitrant acne (Coates et al. 2003 ), chronically
infected tonsils (Chole and Faddis 2003 ), cystic fibrosis (lungs) (Prince 2002 ),
urinary and central venous catheters, and mechanical heart valves (Donlan 2002 ).
A list of microorganisms causing infection due to biofilm growth on tissues or
medical devices is given in Table 1 . Intravascular administration of antibiotics is
used to prevent surgical site and other infections, but the formation of a biofilm
makes antibiotic therapy ineffective at eradicating the bacteria or fungi. The
formation of biofilms with low sensitivity to antibiotics in the course of chronic
infections, such as cystic fibrosis, is a matter of great concern (Il'ina et al. 2004 ).
A range of mucosal to systemic fungal infections have been reported to be
caused by opportunistic pathogen Candida spp. such as oral candidiasis, vaginitis,
and candidemia. Vulvovaginal infections are among the most common infections
caused by C. albicans . Most women experience a vaginal Candida infection at
some point in their lifetimes (Mardh et al. 2002 ). Oropharangeal candidiasis occurs
most commonly in immunocompromised individuals, especially people infected
with HIV and cancer patients (De Repentigny et al. 2004 ; Davies et al. 2006 ).
Recent evidence suggests that the majority of such diseases produced by this
pathogen are associated with biofilm growth (Ramage et al. 2005 ; Hasan
et al. 2009 ; Dongari-Bagtzoglou et al. 2009 ).
The polymicrobial nature of oral biofilms associated with dental plaque and
periodontitis has made them a pioneering model of interspecies interactions and
highlights the level of complexity in biofilm research (Kuramitsu et al. 2007 ;