Prevalence of staphylococcus aureus nasal colonization among HIV-positive and HIV-negative men who have sex with men

Background: Staphylococcus aureus is a ubiquitous microorganism typically colonizing the nasopharynx, skin, and mucous membranes. It is among the most abundant causes of clinically-significant bacterial infections accounting for significant morbidity and mortality among individuals with HIV/AIDS. Evidence of higher colonization rates have been observed, however the majority of previous studies were conducted in clinical settings and estimates have been variable. A community-based cross-sectional study was conducted to determine the prevalence of methicillin-sensitive and methicillin-resistant S. aureus (MSSA, MRSA) nasal colonization among HIV-positive and HIV-negative men who have sex with men (MSM) in the third cycle of the National HIV Behavioral Surveillance System (NHBS) in Houston, Texas. Methods: Between July 2012 - November 2012, nasal swabs were obtained, and microbiologic identification of S. aureus was conducted. Methicillin resistance was determined by oxacillin E-test strips with bacterial inoculums equivalent to a 0.5 McFarland turbidity standard. Results: Of the 202 samples collected, the prevalence of any S. aureus colonization was 29.7% and the prevalence of MRSA colonization was 2.97%. Among HIV-positive participants, MSSA and MRSA colonization was 30.56% and 0%, respectively. Among HIV-negative participants, MSSA and MRSA colonization was 25.90% and 3.61%, respectively. In addition, significant differences for colonization among MSM were observed among individuals participating in receptive and unprotected insertive anal sex (p<.05). Conclusion: The prevalence of S. aureus colonization among HIV-positive MSM is significantly higher than that of the general population. It also supports previous hypotheses that behavioral factors among MSM play a role in S. aureus transmission and colonization.