Current and Emergent Control Strategies for Medical Biofilms - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 131

revealed that lytic action of PlyC destroys the biofilm as it diffuses through the
matrix in a time-dependent fashion, and biofilm rapidly become refractory to
traditional antibiotics.
Phage therapy is very effective in killing drug-resistant strains because of its
specificity toward particular bacterial populations. Formation of a protected biofilm
environment is one of the major causes of the increasing antibiotic resistance
development. These facts emphasize the need to develop alternative antibacterial
strategies, like phage therapy (Cornelissen et al. 2011 ).

4.5 Nature's Own Biofilm Inhibitors

Interest in studying natural products derived from plant sources for the discovery of
new biologically active compounds is not uncommon as many traditional medicines
have been rooted. Some of the most active antibiofilm compounds discovered to
date have been based upon the molecular scaffolds of natural products isolated from
marine natural products (Worthington et al. 2012 ).

4.5.1 Plant Products

The prevention or control of biofilms by interfering with QS systems is one possible
strategy; however, other studies have indicated that phytochemicals can inhibit
interspecies coaggregation (Weiss et al. 1998 ), prevent bacterial adhesion (Kuzma
et al. 2007 ), and inactivate mature single and multispecies biofilms (Niu and Gilbert
2004 ; Knowles et al. 2005 ). There is a novel trend in the antibiofilm research area
toward the identification of natural products, such as plants and their extracts with
antibiofilm activity. Plants offer a virtually inexhaustible and sustainable resource
of very interesting classes of biologically active, low-molecular weight compounds.
Several microbes in complex ecological niches or in association with biofilms
produce compounds that act as antibiofilm agents to gain advantage over others.
Certain marine plants are known to produce compounds that inhibit biofilm forma-
tion in order to prevent microbes from attaching and blocking the sunlight. The best
characterized example is the red algae Delisea pulchra that produces halogenated
furanones to ward off bacterial biofilms (Ren et al. 2004 ). Several marine plants and
microbes have been shown to inhibit biofilm formation.
Plant extracts and essential oils from several medicinal plants have been
exploited as antibiofilm agents for pathogenic biofilm forming bacteria and fungi.
In this respect, xanthorrhizol isolated from Curcuma xanthorrhiza (Rukayadi
et al. 2011 ) and the oil of Boesenbergia pandurata rhizomes (Taweechaisupapong
et al. 2010 ) and Ocimum americanum (Thaweboon and Thaweboon 2009 ) showed
potent in vitro activity against Candida biofilms. Nostro et al. ( 2007 ) studied the
effect of oregano essential oil, carvacrol, and thymol on biofilm made by S. aureus
and Staphylococcus

epidermidis strains. They found that sub-inhibitory