2176. In Vitro Evaluation of Delafloxacin Activity Against Contemporary US Isolates from Cystic Fibrosis Patients Hospitalized with Pneumonia: Results from the SENTRY Antimicrobial Surveillance Program (2019-2021)

BACKGROUND: Delafloxacin (DLX) is a broad-spectrum fluoroquinolone antibacterial approved in the US for the treatment of community-acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections. DLX is indicated to treat CABP caused by multiple pathogens, including methicillin-susceptible Staphylococcus aureus (MSSA) and Pseudomonas aeruginosa (PSA). S. aureus (SA) and PSA are common pathogens causing pneumonia in cystic fibrosis (CF) patients. In this study, the in vitro susceptibilities of DLX and comparator quinolones were determined for clinical isolates from US CF patients collected during 2019-2021. [Figure: see text] METHODS: Isolates from CF patients hospitalized with pneumonia were consecutively collected at 17 US medical centers participating in the SENTRY Surveillance Program. Sites submitted 1 isolate per patient per infection episode. Isolate identification was determined at each site and confirmed using MALDI-TOF at JMI Laboratories. Susceptibility testing was performed according to CLSI broth microdilution methodology. FDA interpretive criteria were used for DLX, and CLSI (2022) criteria were applied to comparators. RESULTS: A total of 115 SA, including 72 MSSA and 67 PSA, were submitted. Susceptibilities (%S) to DLX, levofloxacin (LEV), and moxifloxacin (MOX) for MSSA are shown in the table. As MOX does not have breakpoints for PSA, ciprofloxacin (CIP) was tested. Against all SA, %S was 73.9%, 67.0%, and 67.0% for DLX, LEV, and MOX, respectively. DLX had the highest %S against MSSA (94.4%). The %S to LEV and MOX was 87.5% and 87.5%. DLX was also more active than comparators against PSA, with DLX 68.7%S, while LEV was 43.3%S and CIP was 50.7%S. CONCLUSION: DLX had good activity against recent CF isolates from US hospitals, and had the highest percent susceptibility of the quinolones tested against MSSA and PSA. These in vitro data suggest that DLX could be a useful therapy when coverage of both MSSA and PSA is needed. DISCLOSURES: Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support Jennifer M. Streit, BS, MT(ASCP), Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Shionogi: Grant/Research Support Michael D. Huband, BS, AbbVie: Grant/Research Support|Melinta: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support.