Impact of neutropenia on the clinical outcomes of Staphylococcus aureus bacteremia in patients with hematologic malignancies: a 10-year experience in a tertiary care hospital

Staphylococcus aureus bacteremia is one of the most serious bacterial infections and may lead to worse clinical outcomes in patients with prolonged severe neutropenia. However, clinical data on S. aureus bacteremia in neutropenic patients with hematologic malignancies are limited. We conducted two case-control studies using a 10-year prospective cohort of patients with S. aureus bacteremia. Neutropenic and non-neutropenic hematologic malignancy patients were compared on clinical characteristics and treatment outcomes. An additional matched case-control study using solid tumor patients was conducted. Risk factors for 12-week mortality were analyzed. Of 1643 patients with S. aureus bacteremia, 64 (3.9%) neutropenic and 108 (6.6%) non-neutropenic patients with hematologic malignancies were included in the study. There were no significant differences in the incidence of metastatic infection between the two groups (17.2% vs. 17.6%, p = 0.95), in contrast with a previous study that observed no metastatic infection in neutropenic patients. Twelve-week mortality in neutropenic patients with hematologic malignancies tended to be lower than in non-neutropenic patients with hematologic malignancies (15.6% vs. 26.9%, p = 0.09) and was significantly lower than in neutropenic patients with solid tumors (15.6% vs. 45.8%, p = 0.003). Independent risk factors for mortality in hematologic malignancy patients with S. aureus bacteremia were high Charlson comorbidity score, high APACHE II score, and skin and soft tissue infection. Neutropenia was not independently associated with mortality. Our findings suggest that neutropenia in hematologic malignancies may not affect the incidence of metastatic infection or 12-week mortality of S. aureus bacteremia.