The purpose of this study is to investigate the role of T helper 17 cells (Th17) in the pathogenesis of MRSA infections.

All participant inclusion criteria:

• Greater or equal to 18 years of age
• Willingness to undergo blood draw. Skin biopsy will be requested, but is optional

-AND-

HIV-positive and MRSA-negative Group:

• Documented positive HIV test result
• Negative colonization swabs for S. aureus within 14 days of enrollment
• No evidence of skin/soft tissue infection

HIV-positive and MRSA-Colonization Group:

• Documented positive HIV test result
• History of of colonization with MRSA w/in 14 days of study enrollment

HIV-positive and MRSA Infection Group:

• Documented positive HIV test result
• Skin/soft tissue infection with a positive wound culture showing MRSA within 7 days of enrollment
• MRSA infection is not associated with an intravenous catheter or other nosocomial procedure

HIV Negative groups:

• Same criteria used for the HIV-negative groups as listed above.
• No history of HIV infection.
• Willing to undergo an HIV blood test, which must have a negative result.

Exclusion Criteria:

• Women with positive urine pregnancy test within 7 days of study enrollment
• Women who are within 6 months of being postpartum or who are currently breastfeeding
• Subjects unable or unwilling to complete questionnaires and blood draw.

HIV-positive and negative patients with a recent screen for MRSA colonization or a history of MRSA infection will be asked to participate. Participants will be recruited by providers within the infectious disease clinics at the sites. In addtion, MRSA isolates will be monitored at the central laboratory and providers of patients with MRSA will be notified and asked to notify their patients of the opportunity to participate in this study.