First Report of Treatment-Emergent Resistance to Cefepime-Zidebactam in Pseudomonas aeruginosa.

Dorazio, Ava J; Aitken, Samuel L; Pierce, Virginia M; Kline, Ellen G; Squires, Kevin M; Pogue, Jason M; Shields, Ryan K · Clin Infect Dis · 2026

case_report · Level V

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Abstract

We describe the first case of cefepime-zidebactam treatment-emergent resistance associated with clinical failure in a patient with Pseudomonas aeruginosa pneumonia. During treatment, cefepime-zidebactam minimum inhibitory concentrations increased from 8/8 to 32/32 mg/L. Whole-genome sequence analysis showed new mutations in the MexAB-OprM efflux operon that were associated with cross-resistance to ceftazidime-avibactam and imipenem-relebactam.

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