Prevention of peritransplantation viridans streptococcal bacteremia with early vancomycin administration: a single-center observational cohort study.

Background: Viridans streptococcal bacteremia (VSB) after allogeneic hematopoietic stem cell transplantation (HSCT) is associated with substantial mortality. Prevention of this serious complication is therefore a high priority. The objective of this study was to evaluate the effect of early vancomycin administration on rates and outcomes of VSB.

Methods: We analyzed the effect of early vancomycin on the incidence of VSB in a cohort of 430 consecutive HSCTs performed during the period of 1 January 1998 to 30 September 2002. The primary end point was time to diagnosis of VSB. Early vancomycin was defined as >or=2 doses of vancomycin between days -7 through +7 after HSCT or diagnosis of VSB, whichever occurred first. Risk factors for VSB were identified in univariate and multivariate Cox proportional hazard models.

Results: The incidence of VSB in the cohort was 7.4%. The incidence of VSB in patients who did not receive early vancomycin was 24.8%, compared with 0.3% in patients who did (P<.001). Additional risk factors were female sex, conditioning with total body irradiation, and diagnosis of chronic myelogenous leukemia.

Conclusions: The attributable mortality rate for VSB in our cohort was 21%. Early vancomycin was associated with decreased VSB (hazard ratio, 0.02; 95% confidence interval, 0.003-0.19) after controlling for age, sex, underlying disease, and transplantation variables. The benefits of vancomycin prophylaxis for the prevention of VSB and associated mortality need to be evaluated in a prospective clinical trial.