Location of Thesis Examination

Room 3021 Dental Science Building

Degree

Master of Science

Program

Microbiology and Immunology

Supervisor

Martin McGavin and David Heinrichs

Delay of Publication

1

Abstract

Staphylococcus aureus is a common pathogen that has the ability to infect virtually every tissue and organ system of the body. Despite its propensity to cause invasive infection, S. aureus is also a commensal organism, asymptomatically colonizing ~25% of the population. Much research has gone into resolving this paradox, focusing on both human and bacterial factors that may contribute to colonization. Antimicrobial fatty acids present on the skin and in the nasal mucosa are important components of the innate immune system, and thus we undertook to further understand how S. aureus responds to these fatty acids, and how this response facilitates survival during colonization, or promotes the transition from colonization to infection. Using physiological concentrations of several different fatty acids present on the skin and in the nasal mucosa, we assessed the response of community acquired methicillin resistant S. aureus (CA-MRSA) to long chain fatty acids. 25mM of several unsaturated fatty acids including linoleic (C18:2), palmitoleic (C16:1), sapienic (C16:1), and linolenic (C18:3) added to the culture media was not growth inhibitory, yet caused a marked increase in the expression of the secreted proteases comprising the Staphylococcal proteolytic cascade (SPC). The increase in the expression of proteases was associated with the processing of the lipase glycerol ester hydrolase (Geh) into its mature form. This was not observed in a protease null mutant.