1587. Activity of Ceftolozane/Tazobactam against Gram-Negative Isolates from Lower Respiratory Tract Infections – SMART United States 2018

BACKGROUND: Ceftolozane/tazobactam (C/T) is an antipseudomonal cephalosporin combined with a β-lactamase inhibitor. C/T has been approved by the FDA and EMA for complicated urinary tract infections, complicated intraabdominal infections, and hospital-acquired and ventilator-associated bacterial pneumonia. Using isolates collected in the United States as part of the global SMART surveillance program, we evaluated the activity of C/T and comparators against gram-negative pathogens collected from patients with lower respiratory tract infections (LRTI). METHODS: In 2018, 24 hospitals in the US each collected up to 100 consecutive aerobic or facultative gram-negative bacilli (GNB) from LRTI for a total of 1773 isolates. MICs were determined using CLSI broth microdilution and breakpoints. C/T-nonsusceptible (NS) Enterobacterales and P. aeruginosa isolates were screened by PCR and sequencing for genes encoding β-lactamases. RESULTS: The 3 most common species collected from LRTI were P. aeruginosa (35.0% of all collected GNB), K. pneumoniae (10.4%), and E. coli (9.6%). Enterobacterales and P. aeruginosa combined comprised 86.3% of all collected LRTI GNB. The activity of C/T and comparators against GNB from LRTI is shown in the table. C/T was active against 93% of Enterobacterales isolates from LRTI (activity only exceeded by meropenem and amikacin), as well as against 97% of P. aeruginosa and 94% of all Enterobacterales and P. aeruginosa combined (activity only exceeded by amikacin). C/T maintained activity against 69-83% of β-lactam-NS subsets of Enterobacterales and P. aeruginosa combined. Among 67 molecularly characterized C/T-NS Enterobacterales isolates, 19.4% carried KPC, 1.5% acquired AmpC, and 16.4% only extended-spectrum β-lactamases. No acquired β-lactamases were detected in the remaining 62.7% of isolates, of which 92.9% were species with intrinsic AmpC. Among 21 molecularly characterized C/T-NS P. aeruginosa, one isolate carried an IMP-type metallo-β-lactamase, and in the remaining isolates no acquired β-lactamases were detected. Table [Image: see text] CONCLUSION: With its broad coverage of Enterobacterales and P. aeruginosa, C/T can provide an important empiric therapy option for patients with LRTI in the US. DISCLOSURES: Sibylle Lob, PhD, IHMA (Employee)Pfizer, Inc. (Consultant) Daryl DePestel, PharmD, BCPS-ID, Merck & Co, Inc (Employee) Katherine Young, MS, Merck & Co., Inc. (Employee, Shareholder)Merck & Co., Inc. (Employee, Shareholder) Mary Motyl, PhD, Merck & Co, Inc (Employee, Shareholder) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor)