Electronic Thesis and Dissertation Repository


Master of Science


Microbiology and Immunology


Dr. Martin J. McGavin

2nd Supervisor

Dr. David E. Heinrichs

Joint Supervisor


Community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) strain USA300 has rapidly achieved pandemic status in the community setting. To persist on human hosts, USA300 requires mechanisms to overcome innate immune defenses of the skin, which include antimicrobial unsaturated free fatty acids (uFFAs). This study evaluated efflux mediated mechanisms of resistance to uFFA. tet38 encoding an efflux pump that was previously implicated in resistance to palmitoleic acid, was found to have no role in resistance to uFFA. Conversely, the farE encoded efflux pump conferred resistance to linoleic and arachidonic acid, but not palmitoleic acid. farE expression was induced by uFFA, but not other stresses, and in a fatty acid kinase deficient fakA mutant unable to incorporate uFFA into phospholipid, farE was constitutively expressed, resulting in increased resistance to uFFA. These findings establish that farE is expressed in response to the metabolism of exogenous uFFA in S. aureus, and confers an efflux-mediated mechanism of resistance.

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