Prior antimicrobials and staphylococcal bacteremia in HIV-infected patients

Many drugs used for prophylaxis against opportunistic infections in AIDS also have activity against common bacteria. This study was performed to delineate relationships between prior use of antimicrobials and Staphylococcus aureus bacteremia.

To compare prior exposure to selected antimicrobial drugs in patients who had S. aureus bacteremia and in controls who did not, a nested case-control study was conducted within a cohort of HIV-infected persons followed in an outpatient clinic.

Using a computerized database based on HIV clinic records, 48 cases with S. aureus bacteremia were compared against 188 controls selected from patients with CD4 cell counts < 200 x 10(6)/l. Information on demographic risk factors and antimicrobial drug use was analysed using conditional logistic regression.

Injecting drug use was strongly associated with S. aureus bacteremia. Rifabutin use was associated with decreased risk of S. aureus bacteremia [conditional relative risk (RR) 0.308, 95% confidence interval (CI) 0.096-0.991] in univariate analysis, near statistical significance in multivariate analysis (RR 0.314, 95% CI 0.096-1.023). The bacteremias were not significantly associated with use of trimethoprim-sulfamethoxazole, quinolones, newer macrolides (azithromycin and clarithromycin), clindamycin or dapsone.

Rifabutin may be associated with diminished risk of S. aureus bacteremia incidental to use for other purposes in HIV infection. Further study is needed to assess effects on microbial resistance.