• Mario Tumbarello, Katleen de Gaetano Donati, Evelina Tacconelli, Rita Citton, Teresa Spanu, Fiammetta Leone, Giovanni Fadda, and Roberto Cauda.
• Department of Infectious Diseases and Microbiology, Catholic University, Largo A. Gemelli 8, 00168 Roma, Italy. tumbarello@rm.unicatt.it
• J. Antimicrob. Chemother. 2002 Sep 1;50(3):375-82.

ObjectivesTo define the incidence, risk factors and short-term predictors of mortality of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in HIV-infected patients.Patients And MethodsAll HIV-infected subjects with S. aureus bacteraemia were consecutively enrolled in a case-control study between January 1, 1991 and December 31, 2000 and prospectively followed up.ResultsIn the study period, 129 of 419 (31%) HIV-infected patients with bacteraemia had a diagnosis of S. aureus bacteraemia. The comparative analysis of incidence of S. aureus bacteraemia in the period 1991-96 and 1997-2000 showed a significant decrease (P < 0.001). The same trend was observed for MRSA bacteraemia (P = 0.002). The analysis of antimicrobial resistance showed that among 129 S. aureus strains, 88 (68%) were methicillin susceptible and 41 (32%) were methicillin resistant. The majority of MRSA bacteraemia was hospital acquired (78%). Previous administration of beta-lactams (P < 0.001), multiple previous hospital admissions (P < 0.001) and low numbers of CD4+ peripheral cells (P < 0.001) were found to be independent risk factors of methicillin resistance at multivariate analysis. The mortality rate was 34% in the cases and 11% in the controls (P = 0.002). Multivariate analysis indicated that a high Acute Physiology and Chronic Health Evaluation (APACHE) III score (P < 0.001) and high HIV viraemia (P = 0.02), but not methicillin resistance, predicted an increased risk of death in patients with S. aureus bacteraemia.ConclusionIndividual exposure to beta-lactams, in association with a history of multiple hospitalizations and low CD4+ cell number, plays a pivotal role as a risk factor for the development of methicillin resistance in HIV-infected patients. Methicillin resistance does not influence the outcome of S. aureus bacteraemia when included in a multivariate analysis.

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