Inhibition of Fungal Biofilms - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 267

Histoplasma, Saccharomyces, Trichosporon, Blastoschizomyces, Pneumocystis,
and some zygomycetes (reviewed in Fanning and Mitchell 2012 ; Pitangui
et al. 2012 ; Ramage et al. 2009 ). For example, the opportunistic yeast Cryptococcus
neoformans causes life-threatening meningitis in immune deficient individuals,
particularly HIV-infected patients. This encapsulated yeast can colonize and sub-
sequently form biofilms on ventricular shunts, peritoneal dialysis fistulas, and
cardiac valves (Martinez and Casadevall 2007 ; Martinez et al. 2006 ; Ravi
et al. 2009 ). Different Trichosporon species (also opportunistic yeasts) have been
associated with biofilm formation on catheters, breast implants, and cardiac grafts
(Krzossok et al. 2004 ; Pini et al. 2005 ; Reddy et al. 2002 ). Cushion et al. postulated
that the attachment and growth of Pneumocystis spp. within the lung alveoli
resembles a biofilm and developed in vitro methods for the formation and suscep-
tibility testing of Pneumocystis biofilms (Cushion and Collins 2011 ; Cushion
et al. 2009 ). Invasive aspergillosis caused by Aspergillus spp. is now a major
problem at cancer treatment centers and solid organ transplantation units (Patterson
et al. 2000 ), with recent studies pointing to a role for biofilms in different manifes-
tations of these infections (i.e., prosthetic valve endocarditis) and in the overall
pathogenesis of aspergillosis (Loussert et al. 2010 ; Mowat et al. 2009 ; Muszkieta
et al. 2013 ). A case report described a patient with recurrent meningitis associated
with a Coccidioides immitis biofilm at the tip of a ventriculo-peritoneal shunt
(Davis et al. 2002 ). A recent report described Histoplasma capsulatum attachment
to pneumocyte cells and subsequent biofilm formation (Pitangui et al. 2012 ). In
contrast to Candida , which as a strict commensal is only found inside the host, some
of these fungi are ubiquitous in nature and it is entirely possible that formation of
these attached microbial communities can also contribute to their survival in the
environment (Martinez and Casadevall 2007 ; Ravi et al. 2009 ; Pini et al. 2005 ).
2 Fungal Biofilm Formation and Structural
Characteristics of Fungal Biofilms
Traditionally, techniques used for fungal biofilm formation were cumbersome and
allowed for the formation of only a few biofilms at a time (Ramage et al. 2005 ).
However, more recent research on fungal biofilms has been greatly simplified and
expedited by the development of relatively simple methodologies, most notably the
96-well microtiter plate model for the formation of fungal biofilms (Pierce
et al. 2008 ; Ramage et al. 2001a ). This technique involves the formation of multiple
equivalent fungal biofilms on the bottom of wells of microtiter plates, combined
with a colorimetric method that measures the metabolic activities of cells within the
biofilm. Although originally developed for Candida , it was subsequently adapted
for Cryptococcus , Aspergillus, and other fungi (Martinez and Casadevall 2007 ;
Mowat et al. 2009 ; Pierce et al. 2008 ; Ravi et al. 2009 ). Overall this microtiter plate-
based model of biofilm formation offers an easy, economical, flexible, and robust