2278. Emergence of Resistance and Associated Mortality during Persistent Pseudomonas aeruginosa Bacteremia in Hematopoietic Cell Transplant Recipients and Hematologic Malignancy Patients

BACKGROUND: Pseudomonas aeruginosa (PSA) bacteremia causes significant mortality in patients with hematologic malignancies (HM) and hematopoietic cell transplant (HCT) recipients in part due to intrinsic and acquired resistance mechanisms. However, the incidence of developing resistance on therapy and the associated outcomes are poorly described. We characterize the emergence of resistance on therapy and describe the outcomes of PSA bacteremia in this population. METHODS: We conducted a retrospective review of adults with HM and HCT recipients who developed PSA bacteremia between January 2012 and April 2018. A bacteremic episode was characterized as ≤ 14 days from the first positive blood culture. Persistent bacteremia was defined as a positive blood culture ≥ 72 hours of appropriate antibiotic therapy. Susceptibility testing was performed with VITEK2. Isolates were classified as “sensitive,” “intermediate,” or “resistant” per standard criteria; “intermediate” and “resistant” results were considered “non-susceptible.” RESULTS: 66 episodes of PSA bacteremia occurred in 59 patients. Among episodes in which a patient survived for ≥3 days, 8 (12.1%) met criteria for persistent bacteremia. Non-susceptibility to therapy developed in 5 of 7 episodes (71.4%) of persistent bacteremia; 1 did not have susceptibilities performed on both isolates. Patients with persistent bacteremia had a second positive blood culture within a median of 3.5 days. A concomitant visceral nidus of infection (pneumonia = 6, soft tissue = 1) (P = 0.005) was identified as the primary risk factor for persistent bacteremia. Risk factors for emergence of non-susceptibility could not be determined due low number of events. Infection associated mortality (IAM) (death ≤ 14 days) occurred in 12 (17.1%) of all episodes and 6 of 8 (75%) of persistent bacteremia. Persistent bacteremia was the only risk factor associated with IAM (P = 0.0002, RR 7.3). CONCLUSION: Emergence of resistance to anti-Pseudomonal β-lactam antibiotics frequently occurs during treatment for persistent PSA bacteremia in HCT recipients and HM patients. Persistent bacteremia is associated with a visceral nidus of infection and was the only independent predictor of IAM. DISCLOSURES: All authors: No reported disclosures.