1719. In Vitro Activity of Ceftazidime-avibactam and Comparator Agents against Enterobacterales and Pseudomonas aeruginosa Collected from Patients with Bloodstream Infections as Part of the ATLAS Global Surveillance Program, 2017-2020

BACKGROUND: Avibactam (AVI) is a β-lactamase inhibitor with potent inhibitory activity against Class A, Class C, and some Class D serine β-lactamases. The use of ceftazidime (CAZ) with AVI is approved for several indications. This study evaluated the in vitro activity of CAZ-AVI and comparators against Enterobacterales (Eba) and Pseudomonas aeruginosa (Pae) isolated from the blood of infected patients as part of the ATLAS surveillance program in 2017-2020. METHODS: A total of 67326 Eba and 23051 Pae non-duplicate clinically significant isolates, including 14216 Eba and 3002 Pae isolated from bloodstream infections, were collected in 56 countries in Europe, Latin America, Asia/Pacific (excluding mainland China), and the Middle East/Africa region. Susceptibility testing was performed by CLSI broth microdilution. Meropenem-nonsusceptible (MEM-NS) Eba and Pae isolates were screened for the presence of β-lactamase genes. Only 25% of MEM-NS Pae collected in 2020 were screened. RESULTS: Of all isolates collected, 97.3% Eba and 90.4% Pae were susceptible to CAZ-AVI (MIC(90) values of 0.5 and 8 µg/ml, respectively), more than any comparator tested (table). This was true of blood isolates as well, with 96.9% (Eba) and 90.4% (Pae) isolates susceptible to CAZ-AVI. CAZ-AVI was active against 89.9% of Eba collected from blood that were CAZ-nonsusceptible (NS), more than the comparators tested. While this was not true of CAZ-NS Pae blood isolates (52.9% susceptible to CAZ-AVI), the next most active comparator, amikacin, was active against only 3.9 percentage points more isolates. More MEM-NS isolates that screened negative for MBLs were susceptible to CAZ-AVI than any comparator tested (97.8% of Eba and 80.1% of Pae). [Figure: see text] CONCLUSION: CAZ-AVI provides a valuable therapeutic option for treating bloodstream infections caused by Eba and Pae, except those carrying MBLs. DISCLOSURES: All Authors: No reported disclosures.