Community-Associated Methicillin-Resistant Staphylococcus aureus in High-risk Groups of HIV Patients

The community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and Human Immunodeficiency Virus (HIV) epidemics have intersected. So, we examined the epidemiology of CA-MRSA nasal colonization among 3 groups of HIV-infected and a group of HIV-negative outpatients. We determined prevalence and risk factors associated with MRSA colonization among women, recently incarcerated, and Hispanic HIV-infected patients and among HIV-negative medical patients; isolates were typed by pulsed-field gel electrophoresis (PFGE). Relative prevalence was calculated using poisson regression and logistic regression was used for multivariate analysis. Of 601 patients, 9.3% were colonized with MRSA; 11% of HIV and 4.2% of HIV-negative patients were colonized (relative prevalence = 2.6; 95% CI, 1.12, 6.07; p = 0.03). Among HIV-infected patients, recently incarcerated patients had the highest colonization prevalence (15.6%) followed by women (12%); Hispanic patients had lowest (2.8%). Eighty percent of confirmed MRSA isolates were identified as USA300. On multivariate analysis, history of incarceration or residence in alternative housing (OR = 2.3; 95% CI, 1.1, 4.7; p = 0.03) was associated with MRSA colonization; Hispanic ethnicity was negatively associated (OR = 0.3; 95% CI, 0.11, 0.98; P = 0.045). There was a trend (OR = 1.6; 95% CI, 0.9, 3; p = 0.097) toward geographic location of residence being associated with colonization. After controlling for incarceration, residence, and geography, HIV status no longer was significantly associated with colonization. We identified at-risk outpatients with high levels of CA-MRSA colonization. In certain populations, community exposures may be more important for predicting CA-MRSA colonization than HIV status. Examination of networks of individuals—both HIV-positive and negative—released from incarceration is needed to assess the role of social networks in spread of CA-MRSA and inform prevention strategies.