University of Western Ontario - Electronic Thesis and Dissertation Repository

Location of Thesis Examination

Room 3021 Dental Science Building


Master of Science


Microbiology and Immunology


Dr. Joaquin Madrenas and Dr. Gregory A. Dekaban

Delay of Publication



Staphylococcus aureus is a human pathogen with the potential to cause life-threatening diseases, but it can also be found as a commensal in up to 50% of the population. Its main reservoir is located in the nostrils, where macrophages are the principal mucosal APC and elicit a predominantly IL-10 response. Induction of IL-10 requires phosohoinositide 3-kinase activity, upon stimulation with S. aureus ligands through toll-like receptor 2 binding. It is hypothesized that IL-10 production by macrophages in the nasal mucosa allows S. aureus to persist in this niche as a commensal. To test this hypothesis, a cohort of S. aureus nasal carriers and non-carriers was developed and cytokine responses were compared between these groups. The data suggest that carriers may be producing more IL-10 than non-carriers, while TNF-α production remained unchanged, in response to heat-killed S. aureus. This differential IL-10 production could be a key factor behind S. aureus commensalism.