In vitro activity of cefiderocol, cefepime/enmetazobactam, cefepime/zidebactam, eravacycline, omadacycline, and other comparative agents against carbapenem-non-susceptible Pseudomonas aeruginosa and Acinetobacter baumannii isolates associated from bloodstream infection in Taiwan between 2018-2020.

Background/purpose: This study aimed to investigate the in vitro susceptibilities of carbapenem-non-susceptible Pseudomonas aeruginosa (CNSPA) and Acinetobacter baumannii (CNSAB) isolates to cefiderocol, novel β-lactamase inhibitor (BLI) combinations, new tetracycline analogues, and other comparative antibiotics.

Methods: In total, 405 non-duplicate bacteremic CNSPA (n = 150) and CNSAB (n = 255) isolates were collected from 16 hospitals in Taiwan between 2018 and 2020. Minimum inhibitory concentrations (MICs) were determined using the broth microdilution method, and susceptibilities were interpreted according to the relevant guidelines or in accordance with results of previous studies and non-species-related pharmacokinetic/pharmacodynamic data.

Results: Among the isolates tested, cefiderocol demonstrated potent in vitro activity against CNSPA (MIC, 0.25/1 mg/L; 100% of isolates were inhibited at ≤4 mg/L) and CNSAB (MIC, 0.5/2 mg/L; 94.9% of isolates were inhibited at ≤4 mg/L) isolates. More than 80% of CNSPA isolates were susceptible to cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, and amikacin, based on breakpoints established by the Clinical and Laboratory Standards Institute. Activities of new BLI combinations varied significantly. Tetracycline analogues, including tigecycline (MIC, 1/2 mg/L; 92.5% of CNSAB isolates were inhibited at ≤2 mg/L) and eravacycline (MIC, 0.5/1 mg/L; 99.6% of CNSAB isolates were inhibited at ≤2 mg/L) exhibited more potent in vitro activity against CNSAB than omadacycline (MIC, 4/8 mg/L).

Conclusions: The spread of CNSPA and CNSAB poses a major challenge to global health. Significant resistance be developed even before a novel agent becomes commercially available. The development of on-site antimicrobial susceptibility tests for these novel agents is of great clinical importance.