195 - Antimicrobial Stewardship Incorporating New Antimicrobials for Use against Multi-Drug Resistant Pseudomonas aeruginosa in Cystic Fibrosis

Background: Cystic fibrosis (CF) is a life-limiting genetic disease affecting approximately 80,000 people worldwide, including 30,000 in the United States. Chronic Pseudomonas aeruginosa (PA) infections in CF often develop to be multidrug-resistant (MDR) and are associated with worse clinical outcomes. Ceftolozane/Tazobactam (C/T) has shown benefits over other standards of therapy in selected populations with MDR-PA infections, but studies are lacking in the CF population. The objective of this study was to evaluate the current use and antimicrobial stewardship of C/T in CF patients with MDR-PA.

Methods: This is a retrospective study of hospitalized CF patients with infections due to positive cultures for MDR-PA from 2016-2019 at Baylor St. Luke’s Medical Center in Houston, Texas. Electronic medical records were reviewed for patient demographics, presence of infectious diseases (ID) consult, antibiotics use, and clinical outcomes. A descriptive analysis was performed to compare the patient demographics and clinical outcomes between patients receiving C/T-based and non-C/T therapies.

Results: A total of 56 CF patients with positive MDR-PA cultures were identified (18 receiving C/T and 38 receiving non-C/T antibiotics). Most MDR-PA was cultured from the lungs (94.6%, 54/56). Patient age, weight, and body mass index were similar between those receiving C/T and non-C/T therapies as was the overall duration of antibiotic therapy 16.3 (± 8.7) vs. 13.9 (± 3.5) days in C/T and non-C/T groups, respectively. More patients in the C/T group had severe forced expiratory volume in 1 s (FEV₁) [ £40%] at baseline (66.7% vs. 21.1%) and higher ICU admission rates (44.4% vs 2.6%). All C/T patients had an ID consult placed (3 ± 3.1 days after admission) but none in the non-C/T group. The 30-day recurrent pulmonary exacerbation rate was comparable between C/T and non-C/T groups (22.2% vs. 15.8%).

Conclusion: C/T was reserved for the sickest group of CF patients with severe FEV₁. Given the devastating disease progression with MDR organisms in CF, new antibiotics with better clinical outcomes against chronic MDR-PA should be considered earlier in therapy for this population. Larger studies are warranted to analyze cost-effectiveness and clinical outcomes.