RT Journal Article T1 Imipenem-Relebactam Susceptibility in Enterobacterales Isolates Recovered from ICU Patients from Spain and Portugal (SUPERIOR and STEP Studies). A1 Hernández-García, Marta A1 García-Castillo, María A1 Bou, Germán A1 Cercenado, Emilia A1 Delgado-Valverde, Mercedes A1 Oliver, Antonio A1 Pitart, Cristina A1 Rodríguez-Lozano, Jesús A1 Tormo, Nuria A1 Melo-Cristino, José A1 Pinto, Margarida F A1 Gonçalves, Elsa A1 Alves, Valquíria A1 Vieira, Ana Raquel A1 Ramalheira, Elmano A1 Sancho, Luísa A1 Diogo, José A1 Ferreira, Rui A1 Cruz, Hugo A1 Chaves, Catarina A1 Duarte, Joana A1 Pássaro, Leonor A1 Díaz-Regañón, Jazmín A1 Cantón, Rafael K1 ICU patients K1 Portugal K1 Spain K1 carbapenemase-producing Enterobacterales K1 imipenem-relebactam susceptibility AB Imipenem-relebactam is a novel β-lactam-β-lactamase inhibitor combination. We evaluated the in vitro activity of imipenem-relebactam and comparators against Enterobacterales clinical isolates recovered in 8 Spanish and 11 Portuguese intensive care units (ICUs) (SUPERIOR, 2016-2017; STEP, 2017-2018). Overall, 747 Enterobacterales isolates (378 Escherichia coli, 252 Klebsiella spp., 64 Enterobacter spp., and 53 other species) were prospectively collected from ICU patients with complicated intraabdominal (cIAI), complicated urinary tract (cUTI), and lower respiratory tract (LRTI) infections. MICs were determined (ISO-broth microdilution), and whole-genome sequencing (WGS) was performed in a subset of isolates displaying susceptible and resistant imipenem-relebactam MICs. Imipenem-relebactam (98.7% susceptible) showed similar activity to ceftazidime-avibactam (99.5% susceptible) and higher than ceftolozane-tazobactam (86.9% susceptible). Imipenem-relebactam was inactive against 1.3% (10/747) isolates, all of them due to carbapenemase production (9 K. pneumoniae and 1 E. cloacae). Imipenem-relebactam was active against 100% of extended-spectrum β-lactamase (ESBL)-E. coli and ESBL-Klebsiella spp. isolates and 80.4% of carbapenemase-Klebsiella spp. producers. Carbapenemase genes were confirmed by WGS in 41 Klebsiella spp.: OXA-48 (20/41), KPC-3 (14/41), OXA-181 (4/41), NDM-1 (1/41), OXA-48 + VIM-2 (1/41), and KPC-3 + VIM-2 (1/41). In Klebsiella spp. isolates, relebactam restored imipenem susceptibility in all KPC-3 producers, and resistant isolates (7/41) were mostly OXA-48 + CTX-M-15-K. pneumoniae high-risk clones (7/9). Intercountry differences were detected as follows: OXA-48 (17/21) was dominant in Spain, unlike KPC-3 (14/15) in Portugal. Imipenem-relebactam was 100% active against CTX-M-15-ST131-H30Rx-E. coli high-risk clone, predominant in both countries. Our results depict the potential role of imipenem-relebactam in ICU patients with cIAIs, cUTIs, and LRTIs due to wild-type ESBL- and carbapenemase-producing Enterobacterales, particularly KPC producers. IMPORTANCE We comparatively evaluate the in vitro activity of a drug combination consisting of a carbapenem (imipenem) and a novel inhibitor of beta-lactamases (relebactam), a mechanism that destroys beta-lactam antibiotics. We assess the activity against a collection of Enterobacterales clinical isolates recovered from difficult-to-treat infections in patients admitted to different intensive care units in Portugal and Spain. Imipenem-relebactam shows excellent activity in avoiding common resistance mechanisms in this setting, such as extended-spectrum beta-lactamases and carbapenemases widely distributed, including KPCs. We show few resistant isolates ( YR 2022 FD 2022-08-31 LK http://hdl.handle.net/10668/20046 UL http://hdl.handle.net/10668/20046 LA en DS RISalud RD Apr 3, 2025