BackgroundExtensively drug-resistant (XDR) P. aeruginosa (PA), defined as resistant to ≥ 1 agents in all classes of antibiotics except two classes, limits therapeutic options to more toxic agents such as aminoglycosides (AMG) and polymyxins. Majority of the XDR PA isolated in two of our teaching hospitals were found to be susceptible to ceftolozane–tazobactam (CT) in addition to AMG and polymyxins. Our study aims to compare treatment outcomes with traditional antibiotics vs. CT in patients with XDR PA pneumonia.MethodsThis is a retrospective case–control study of patients admitted to two local hospitals from 2013 to 2018. Patients were screened by discharge diagnosis for pneumonia. We included patients over 18 years with XDR PA in sputum cultures susceptible to ≤ 2 classes of antibiotics. Statistical analyses included ANOVA, T-test, Fisher exact and Chi-square tests.ResultsAmong the 48 patients with XDR PA pneumonia, 33 patients met inclusion criteria. Their mean age was 62 years (SD ±16), 30% were female, and 18% were immunocompromised. Similarly, 85% of patients had underlying lung disease and 55% had a tracheostomy tube. Majority of these patients were either nursing home residents (55%) or hospitalized (46%) within past 3 months. Septic shock associated with XDR PA pneumonia was found in 30% of patients, and 73% required mechanical ventilation during treatment. Nineteen patients received an aminoglycoside (AMG group), 1 colistin, 9 CT (CT group), and 4 received CT plus an AMG. The average time to clinical improvement was 3.5 (±2.2) days for AMG group and 2.2 (±1.7) days for CT group (P = 0.3). Compared with CT group, AMG group had significantly longer mean duration of hospital stay (19 ± 13 vs. 32.4 ± 17 days, P < 0.05). All patients who had clinical failure to improve requiring change in antibiotics (2 patients) or who died after withdrawal of care (3 patients) were in AMG group. Clinical relapse within 30 days occurred equally in both groups (4 AMG, 2 CT, P > 0.05). Six patients who developed acute kidney injury received either an AMG (5) or colistin (1).ConclusionBased on our observation, CT is a safe and effective treatment for XDR PA pneumonia. Compared with CT, patients who received AMG had longer hospital stays and sustained more nephrotoxicity.Disclosures All authors: No reported disclosures.