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![](/i/favi32.png) $-AmyloidPeriodontal Disease- Symptoms Treatment and Prevention - Nova Biomedical Books 1 edition January 2011Antimicrobial Activity
Up to the present, there have been an enormous number of
in vitro
studies, showing the
antimicrobial activity of LL-37 and human defensins against various pathogens associated
with a variety of human diseases. All of these studies cannot be completely mentioned in this
chapter due to the space limitation. Therefore, the scope of this topic will be restricted to the
antimicrobial effects on oral pathogens, especially the ones associated with periodontal
disease. In the oral cavity, the warm temperature and moistened mucosal and tooth surfaces
are suitable for microbial colonization and then the formation of biofilm, so-called dental
plaque. The dental plaque is essential for some specific oral microorganisms to survive and
thrive in this complex community. It is conceivable that the exopolysaccharide-producing
plaque can protect oral microorganisms from exposure to antibiotics, or antimicrobial
peptides in the context of this discussion.As with antibiotics, it is, therefore, likely that plaque
microorganisms are more resistant to destructionby antimicrobial peptides than are planktonic
microrganisms present in the saliva. Consequently, antimicrobial peptides can be regarded as
one of the selective pressures that oral microorganisms must overcome in order to establish
colonies in the dental plaque.
Furthermore, it should be emphasized that the results obtained from most studies that
examine the susceptibility of one or more microbial species to individual antimicrobial
peptides
in vitro
may not represent the real effectiveness of antimicrobial peptides due to the
complexity of interactions between host and microorganisms or between two different types
of microorganisms in the dental plaque. However, it is rather difficult to evaluate the
effectiveness of antimicrobial peptides in such a complicated situation
in vivo
. Fortunately,
some recent
in vivo
studies have shed light into the clinical significance of antimicrobial
peptides for periodontal homeostasis. In this regard, it has been shown that genetic and
acquired deficiencies of some antimicrobial peptides are associated with the pathogenesis of
some types of periodontitis (Pütsep et al, 2002; Puklo et al, 2008), and this will be discussed
under the next heading.
Other factors that influence the antimicrobial effects of some antimicrobial peptides are
high salt concentrations that are shown to inhibit antimicrobial functions in other parts of the
body (Goldman et al, 1997; Midorikawa et al, 2003) and the presence of inhibitors in serum
(Tanaka et al, 2000). However, in the oral cavity, antimicrobial peptides may not be affected
by these factors, since the peptides function at the mucosal surface, where the concentrations
of salt or inhibitors, diluted with saliva, are too low to exert any significant inhibitory action.
At the outsetof the study of the antimicrobial effects on oral bacteria, the bactericidal
activity
of
LL-37
was
tested
against
different
strains
of
Aggregatibacter
actinomycetemcomitans
and
Capnocytophaga
spp., which are implicated in the pathogenesis
of juvenile periodontitis and gingivitis, respectively (Tanaka et al, 2000). It was found that the
concentrations of LL-37 (below 12
g/ml) already killed all strains of these two bacteria by
99%. Subsequently, under a more detailed investigation into the antimicrobial effects of LL-
37 against different kinds of periodontal bacteria, involved with various stages of dental
plaque formation, it was demonstrated that the early colonizing yellow-complex bacteria,
such as oral
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