Increasing rates of community-acquired methicillin-resistant Staphylococcus aureus infections among HIV-infected persons.

Community-acquired (CA) methicillin-resistant Staphylococcus aureus (MRSA) rates have rapidly increased in the general population; however, little data on recent incidence rates and risk factors of CA-MRSA infections among HIV patients appear in the literature. A retrospective study was conducted from 1993 through 2005 among patients at a large HIV clinic. Trends in CA-MRSA infection incidence rates, clinical characteristics and risk factors for CA-MRSA were evaluated. Seven percent of our cohort developed a CA-MRSA infection during the study period. The rate of CA-MRSA infections among HIV-infected population significantly increased since 2003, with an incidence of 40.3 cases/1000 person-years in 2005, which was 18-fold higher than the general population served at our facility. In all, 90% of infections were skin/soft tissue infections with a predilection for buttock or scrotal abscess formation; 21% of patients experienced a recurrent infection. Risk factors included a low CD4 count at the time of infection (odds ratio [OR] per 100 CD4 cells 0.84, P = 0.03), high maximum log(10) HIV viral load (OR 4.54, P<0.001), recent use of beta-lactam antibiotics (OR 6.0 for receipt of two prescriptions, P<0.001) and a history of syphilis (OR 4.55, P = 0.01). No patient receiving trimethoprim-sulfamethoxazole prophylaxis developed a CA-MRSA infection. Over the study period, CA-MRSA accounted for an increasing percentage of positive wound cultures and Staphylococcus aureus isolates, 37% and 65%, respectively, during 2005. In conclusion, CA-MRSA infections have rapidly increased among HIV-infected patients, a group which has a higher rate of these infections than the general population. Risk factors for CA-MRSA among HIV-infected patients include low current CD4 cell count, recent beta-lactam antibiotic use and potentially high-risk sexual activity as demonstrated by a history of syphilis infection.