1088. Evaluating the Timing of Antimicrobial Prophylaxis in Allogeneic and Autologous Hematopoietic Stem Cell Transplant

BACKGROUND: Hematopoietic stem cell transplant (HSCT) patients develop profound neutropenia during the transplant process and often fever, which is suggestive of infection. Antimicrobial prophylaxis (AP) during anticipated neutropenia is recommended; however, data regarding when to initiate AP is limited. A local quality improvement initiative adjusted AP initiation to target the duration of severe neutropenia, defined as ANC ≤ 500 mm(3) (ANC500), which is when patients are at the greatest risk of infection. This initiative aimed to reduce antimicrobial utilization and consequences of unnecessary antimicrobial exposure while not adversely affecting patient outcomes. METHODS: A retrospective study was conducted across two cohorts over a 2-year period. The pre-intervention cohort (November 2016–2017) called for the initiation of AP on Day -1 prior to transplant. The post-intervention cohort (November 2017–2018) called for initiation of AP when patients reached ANC500. The primary outcome was frequency of febrile occurrences (temperature ≥38°C). Secondary outcomes included days of antimicrobial exposure, positive blood cultures, all-cause mortality, length of stay, graft-vs.-host disease, and Clostridioides difficile rates. Patients were excluded if they received a haploidentical transplant or inappropriate AP for the specified cohort. RESULTS: A total of 248 patients were included in the final analysis with 130 patients in the pre-intervention cohort and 118 patients in the post-intervention cohort. The final analysis included 40 allogeneic and 208 autologous HSCT patients. There was no difference in fever occurrences between the two groups (79% pre vs. 69% post; P = 0.078). There was a significant reduction in the mean antibacterial (10.3 vs. 4.95; P < 0.001) and antifungal (13.4 vs. 7.6; P < 0.001) prophylaxis per patient-days in the pre- and post-intervention group. No significant differences in positive blood cultures (11.5% vs. 16.9%; P = 0.222), ICU admissions, length of stay or all-cause mortality were identified. CONCLUSION: Delaying antimicrobial prophylaxis (AP) until severe neutropenia showed no difference in fever occurrences or other patient outcomes. This approach is associated with a drastic reduction in antimicrobial exposure. DISCLOSURES: All authors: No reported disclosures.