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Staph Rate Falling in HIV+ Danes, But Still High vs General Population
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50th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), September 12-15, 2010, Boston
Mark Mascolini
Incidence of Staphylococcus bacteremia dropped sharply over the past decade in HIV-infected people assessed in a nationwide Danish study. The decline was much smaller in injecting drug users (IDUs) than in gay men, and Staph incidence remains much higher in people with HIV than the general Danish population.
The study involved all HIV-infected people in care in Denmark from January 1, 1995 through December 31, 2007. The investigators matched each HIV-infected person by age and gender with up to 19 controls in the general population. Follow-up continued until the first episode of Staph bacteremia, death, or emigration. The researchers used time-updated Poisson regression analysis to estimate Staph incidence (the new diagnosis rate).
The analysis included 4871 people with HIV and 92,116 general-population controls assessed in 815,286 person-years of observation. The researchers identified 284 cases of Staph bacteremia--132 in the HIV group and 152 in controls. Those numbers translated into more than a 20 times higher Staph rate in people with HIV (incidence rate ratio [IRR] 20.7, 95% confidence interval [CI] 18.2 to 23.5).
Staph incidence fell almost 70% over the observation period in people with HIV, from 770 per 100,000 person-years in 1995-1998 to 235 per 100,000 in 2003-2007 (IRR 0.31, 95% CI 0.25 to 0.38). But Staph incidence fell less among people infected with HIV when injecting drugs than among men infected during sex with other men:
--IDUs: 2439 to 1507 diagnoses per 100,000 (1995-98 to 2003-07)
--Gay men: 385 to 84 diagnoses per 100,000 (1995-98 to 2003-07)
Declining incidence among heterosexually infected people stood between the rates in IDUs and gays.
CD4 count emerged as the strongest independent predictor of Staph incidence. People with a latest CD4 count below 100 had more than a 10 times higher risk of Staph than did people with a count above 350 (IRR 10.2, 95% CI 8.2 to 12.8). Not taking combination antiretrovirals raised the risk of Staph 80% in IDUs and gay men, while raising the risk 60% in heterosexually infected people. Not having a viral load below 500 copies raised the Staph risk 3.0 times in IDUs, 1.9 times in gays, and 2.2 times in heterosexuals. Ethnicity and gender did not affect Staph incidence.
Reference
Larsen MV, Harboe ZB, Ladelund S, et al. Incidence of and risk factors for Staphylococcus aureus bacteraemia in a nation-wide HIV-infected and uninfected matched cohort study. 50th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). September 12-15, 2010. Boston. Abstract H-235.
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