Have Direct Antimicrobial Effects

The defensins are a family of small antimicrobial peptides with three to four intramolecular cysteine disulfide bonds. They are found in mammals, insects, and plants and are divided on the basis of six conserved cysteine residues into two categories designated a- and jS-defensins (Ganz, 2003). 

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Pharmacology BSS appears to have antisecretory and antimicrobial effects in vitro and may have some anti-inflammatory effects. The salicylate moiety provides the antisecretory effect, while the bismuth moiety may exert direct antimicrobial effects against bacterial and viral enteropathogens. 

Recently, the activities of host defense peptides related to the resolution of infection have been suggested to result in part from nondirect antimicrobial activities. It has been postulated that immunomodulation may represent the primary action of these peptides in vivo as the immunomodulatory activities are retained under physiological conditions in contrast to the direct antimicrobial activities of most natural mammalian host defense peptides. These immunomodulatory activities include, but are not limited to, direct chemotactic activity, induction of chemokines and other immune mediators, stimulation of leukocyte degranulation and other microbicidal activities, effects on leukocyte and epithelial cell survival and apoptosis, stimulation of epithelial and endothelial cell proliferation, promotion of wound healing and angiogenesis, antiendotoxic and anti-inflammatory activities, and adjuvant fiinctions. These will be described in detail in the following sections and a summary is found in Table 1. 

EOs have been used for therapeutic purposes and as cosmetics through human history. Their antimicrobial effects and their use in skin formulations have been known for centuries [82], which probably led to investigatiOTis of their antiviral activities on viral skin diseases. Indeed, human herpes viruses, for example, HSV-1 and HSV-2, are the most investigated viruses with EOs [83-94]. Topical treatments containing extracts from lemon balm and sage extracts are available for herpes labialis [80]. EOs obtained from Santolina insularis [85], Melissa officinalis L. [82], Melaleuca species [87], Houttuynia cordata [88], Australian tea tree and eucalyptus [90], Mentha piperita [91], and Salvia fruticosa [93] exhibited direct inactivation of HSV. 

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