The human pathogen S. aureus is able to cause a large range of diseases, from minor skin diseases to life threatening sepsis. This versatility is governed by an extensive repertoire of virulence determinants and an acute ability to respond to the host environment in order to adapt, survive and proliferate. The problem of S. aureus is exacerbated by the rapid spread of antibiotic resistance, leading to such agents of public concern as methicillin resistant S. aureus (MRSA). There is therefore a desperate need to develop new therapeutic agents against S. aureus. Harnessing human innate defenses may provide a novel mechanism to combat the scourge of MRS A and other antibiotic resistant strains. Human skin fatty acids have been shown to have highly anti staphylococcal activity. In particular the major skin fatty acid cis-6-hexadecenoic acid (C-6-H) is able to rapidly kill S. aureus, by an unknown mechanism. Also C-6-H at concentrations, which do not kill the bacteria, is able to inhibit the production of major virulence determinants. This project aimed to determine the molecular response of S. aureus to C-6-H, a major facet of the human innate defence. Initial experiments showed that exposure to sub-MIC levels of C-6-H resulted in the induction of a resistance mechanism. In order to begin to determine the molecular basis for the induced resistance and the inhibition of virulence determinant production by C-6-H transcriptome and proteome studies were carried out. The transcriptome revealed an altered level of transcription of over 500 genes, in response to sub-MIC C-6-H, which are involved in virulence, amino acid biosynthesis, energy metabolism, stress response, purine and pyrimidine metabolism, cell wall and cell envelope dynamics and several regulatory systems. Interestingly, the expression of the toxins (hla, hlb, hlgBC) was highly reduced in the presence of C-6-H, whereas the expression of genes involved in host defence evasion (cap, sspAB, kalA) were increased. The proteome studies also showed a decrease in the production of several toxins. Members of the SaeRS regulon were reduced in expression, in response to C-6-H and several were confirmed by qRT-PCR. The use of specific mutants revealed the effect of C-6-H on toxin production is likely mediated directly or indirectly via SaeRS. The global effects ofC-6-H on S. aureus physiology are discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:556988 |
| Date | January 2010 |
| Creators | Rauter, Yvonne |
| Publisher | University of Sheffield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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