There is increasing evidence that bacterial compounds
such as cell wall fragments, their metabolites and deadbacteria can elicit certain immune responses on the skin
and improve skin’s barrier function. Cell-free cultures of
lactic acid bacteria with probiotic potentials have been
demonstrated to exert antimicrobial and immunomodulatory activities, suggesting the use of probiotic in nonviable forms (Iordache et al. 2008). Natural cell
components and metabolites may be the preferred choice
in cases where the delivery of live cells is not possible.
Moreover, cell components and metabolites are more stable than viable cells at room temperature and are thus
more suitable for topical applications. Human clinical
studies have suggested that probiotic exert dermal benefits not only through the gastrointestinal route but also
upon topical applications. Using in vitro study, Iordache
et al. (2008) have demonstrated that cell-free cultures of
lactic acid bacteria with probiotic potentials including
Lactobacillus plantarum, Lactobacillus casei and Enterococcus faecium inhibited the expression of soluble virulence
factors by opportunistic dermal pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa and
decreased their adherence capacity to the cellular substrate represented by HeLa cells. Meanwhile, using ex vivo
human skin explants model, Gueniche et al. (2010) found
a statistically significant (P < 005) improvement following application of cell lysate from Bifidobacterium longum
sp. versus placebo in various parameters associated with
inflammation such as a decrease in vasodilation, oedema,
TNF-alpha release and mast cell degranulation. The
potentials of probiotics in dermal application have also
been evaluated in several in vivo studies