1582. Delafloxacin Activity Against Drug-Resistant Streptococcus pneumoniae, Haemophilus influenzae, Haemophilus parainfluenzae, and Moraxella catarrhalis from US Medical Centers (2014–2018)

BACKGROUND: Delafloxacin (DLX) is an anionic fluoroquinolone (FQ) antimicrobial that was approved in 2017 by the United States (US) Food and Drug Administration for the treatment of acute bacterial skin and skin structure infections. DLX recently successfully completed a clinical trial for the treatment of community-acquired bacterial pneumonia (CABP). In the present study, in vitro susceptibility (S) results for DLX and comparator agents were determined for CABP pathogens including Streptococcus pneumoniae (SPN), Haemophilus influenzae (HI), H. parainfluenzae (HP) and Moraxella catarrhalis (MC) clinical isolates from US hospitals participating in the SENTRY Program during 2014–2018. METHODS: A total of 1,975 SPN, 1,128 HI, 684 MC, and 43 HP isolates were collected from community-acquired respiratory tract infections (CARTI) during 2014–2018 from US hospitals. Sites included only 1 isolate/patient/infection episode. Isolate identifications were confirmed at JMI Laboratories. Susceptibility testing was performed according to CLSI broth microdilution methodology, and CLSI (2019) breakpoints were applied where applicable. Other antimicrobials tested included levofloxacin (LEV) and moxifloxacin (MOX; not tested in 2015). Multidrug-resistant (MDR) SPN isolates were categorized as being nonsusceptible (NS) to amoxicillin-clavulanate, erythromycin, and tetracycline; other SPN phenotypes were LEV-NS or penicillin (PEN)-NS. β-Lactamase (BL) presence was determined for HI, HP, and MC. RESULTS: The activities of the 3 FQs are shown in the table. The most active agent against SPN was DLX, with the lowest MIC(50/90) values of 0.015/0.03 mg/L. DLX activities were similar when tested against the MDR or PEN-NS for SPN phenotypes. LEV-NS isolates had DLX MIC(50/90) results of 0.12/0.25 mg/L. DLX was the most active FQ against HI, HP, and MC. BL presence did not affect FQ MIC values for HI or MC; only 2 HP isolates were BL-positive. CONCLUSION: DLX demonstrated potent in vitro antibacterial activity against SPN, HI, HP, and MC. DLX was active against MDR SPN that were NS to the agents commonly used as treatments for CABP. DLX had excellent activity against LEV-NS SPN. These data support the continued study of DLX as a potential treatment for CABP. [Image: see text] DISCLOSURES: All authors: No reported disclosures.