| Summary: | A limited number of studies have investigated the concept of using enteric probiotic bacteria to alter microbial communities in areas other than the gut. The use of enteric probiotics is attractive because they are considered generally as non-pathogenic and safe. The aim of this thesis was to explore the possibility that probiotic bacteria, or material derived from them, have utility for skin in health and disease. Primarily, the thesis investigates whether probiotics can protect skin cells from the effects of the common pathogen, S. aureus, and whether probiotics can accelerate the wound healing process. Furthermore, some of the underlying mechanisms were investigated. In the first study, the potential of probiotics to protect primary human keratinocytes from the effects of S, aureus was investigated. When primary human keratinocytes were exposed to S. aureus, only 25% remained viable following 24h incubation. However, in the presence of 108cfu/ml of live L. rhamnosus GG, the viability of the infected keratinocytes increased to 57%. Interestingly, L. rhamnosus GG lysates and spent culture fluid also provided significant protection to keratinocytes (P=0.006, P=0.01) following the same period of incubation. Keratinocyte survival was enhanced significantly, regardless of whether the probiotic was applied in the viable form, or as cell lysates, 2h before or simultaneously (P=0.005) or 12h after (P=0.01) to S. aureus infection. With respect to mechanism, both L. rhamnosus GG lysate and spent culture fluid apparently inhibited adherence of S. aureus to keratinocytes by competitive exclusion; however, only viable bacteria or the lysate could displace S. aureus (P=0.04 and 0.01 respectively). Furthermore, growth of S. aureus was inhibited by either live bacteria or lysate but not spent culture fluid (Chapter 3). Together, these data suggest at least two separate activities involved in the protective effects of L. rhamnosus GG against S. aureus, growth inhibition and reduction of bacterial adhesion. This idea has been confirmed by partial purification of L. rhamnosus GG lysate. Fractionation of the lysate demonstrated that the protective effect of L. rhamnosus GG lysate depends not only on inhibitory substances, but also on anti-adhesion substances present in the lysate (Chapter 4). The L. rhamnosus GG lysate increased the re-epithelialisation rate of model wounds in vitro in a scratch assay(P=0.02) (Chapter 5). Furthermore, L. rhamnosus GG lysate stimulated the re-epithelialisation of ex-vivo skin cultures (Chapter 6). In vitro and ex-vivo proliferation and migration assays demonstrated that L. rhamnosus GG lysate significantly increased keratinocyte proliferation and migration relative to controls; however, the dominant mechanism was migration (Chapter 5). Therefore, the pathways underlying these effects were explored by doing Affymetrix analysis for genes expressed in response to treatment with L. rhamnosus GG lysate. The results highlight that the CXCR2/CXCL2 and FGF7/FGFR2 are up-regulated, which may mediate the acceleration of re-epithelialisation of keratinocytes through stimulation of cell migration under the effect of L. rhamnosus GG lysate. In summary, these data suggest that L. rhamnosus GG and its extract may be a useful method of counteracting S. aureus infection and reducing the toxicity of pathogens. At the same time, specific probiotic lysates may be useful for improving the wound healing process and ultimately reduce the severity of impaired wounds in the community. Thus, the use of safe probiotic bacteria or lysates presents new options for the development of a new treatment that could improve wound healing while simultaneously reducing infection.
|
|---|
