2217. Frequency and Antimicrobial Susceptibility of Bacteria Isolated from Patients Hospitalized with Pneumonia in US Medical Centers During 2018

Background Rapidly introducing appropriate antimicrobial therapy is crucial to reduce morbidity and mortality of patients hospitalized with pneumonia (PHP), and therapy is determined mostly by understanding causative pathogens. Ceftazidime–avibactam (CAZ-AVI) was recently approved and ceftolozane–tazobactam (C-T) is in late-stage clinical development for treating nosocomial pneumonia, including ventilator-associated. Methods Bacterial isolates were consecutively collected from PHP (1/patient) in 67 US medical centers in 2018 and the Gram-negative bacilli (GNB) were tested by reference broth microdilution methods for susceptibility (S) to CAZ-AVI, C-T, and many comparators at a central laboratory. Results The most common organisms isolated from PHP were S. aureus (27.0%), P. aeruginosa (PSA) (24.6%), K. pneumoniae (KPN; 7.6%), E. coli (6.8%), S. marcescens (5.4%), and S. maltophilia (XM; 4.5%). Colistin (99.7%S), CAZ-AVI (95.7%S), and C-T (94.9%S) were the most active compounds against PSA; CAZ-AVI (99.9%S), amikacin (AMK; 98.8%S), and meropenem (MEM; 97.6%S) were the most active compounds against Enterobacterales (ENT). CAZ-AVI and C-T retained activity against PSA isolates non-S (NS) to piperacillin–tazobactam (PIP-TAZ), MEM, and cefepime (FEP), whereas PSA isolates NS to PIP-TAZ, MEM, or FEP exhibited low S rates to PIP-TAZ (≤ 39.2%), MEM (≤ 37.8%), and FEP (≤ 38.0%; Table). CAZ-AVI and tigecycline were the only compounds with good activity against carbapenem-resistant ENT (CRE), both with 96.6%S. Among ENT, the most common ESBL and carbapenemase were CTX-M-15 (73%) and KPC-2/3 (76%), respectively. CAZ-AVI was active against all ESBL producers (100.0%S), whereas the S rate to C-T was 82.4%. The most active compounds against multidrug-resistant (MDR) ENT were CAZ-AVI (98.9%S), AMK (91.5%S), and MEM (80.8%S). XM and A. baumannii exhibited low S rates to most antimicrobials tested. Conclusion Gram-negative bacteria were isolated from 70% of PHP, and PSA and ENT represented >80% of these organisms. CAZ-AVI and C-T showed similar coverage (%S) against PSA (95.7–94.9%S). In contrast, C-T was less active than CAZ-AVI against ENT in general and exhibited limited activity against ENT-resistant subsets. Disclosures All authors: No reported disclosures.