Electronic Thesis and Dissertation Repository


Master of Science


Microbiology and Immunology


Dr. Martin McGavin


Staphylococcus epidermidis is a ubiquitous skin commensal, and produces a serine protease Esp that can eradicate nasal carriage of the opportunistic pathogen, Staphylococcus aureus. We evaluated the ability of S. epidermidis and S. aureus to express serine protease and compete with one another in response to acidic pH and unsaturated free fatty acids; conditions encountered on human skin. The hypervirulent USA300 strain of S. aureus was more competitive in co-culture conditions of acidic pH or 25 µM palmitoleic acid alone, but could not compete with S. epidermidis when these conditions were combined. Conversely, in pure culture, these conditions promoted abundant expression of the SspA serine protease by S. aureus, but repressed expression of the orthologous Esp protease by S. epiderimidis. Thus, in response to conditions that would be encountered on skin, pathogenic S. aureus maintained production of secreted virulence factors, but S. epidermidis had a competitive growth advantage.

Master's Thesis Supervisor Approval.pdf (939 kB)
Master's Thesis Supervisor Approval