A descriptive case series of pharmacokinetic/pharmacodynamic target attainment and microbiological outcome in critically ill patients with documented severe extensively drug-resistant Acinetobacter baumannii bloodstream infection and/or ventilator-associated pneumonia treated with cefiderocol

ABSTRACT: Objectives: The aim of this study was to explore the relationship between cefiderocol pharmacokinetic/pharmacodynamic (PK/PD) target attainment and microbiological outcome in critically ill patients affected by extensively drug-resistant Acinetobacter baumannii (XDR-AB) bloodstream infection (BSI) and/or ventilator-associated pneumonia (VAP). Methods: Patients who received compassionate use of cefiderocol to treat documented XDR-AB infections at the intensive care unit of the IRCCS Azienda Ospedaliero–Universitaria of Bologna and who underwent therapeutic drug monitoring (TDM) from 15 March 2021 to 30 April 2021 were retrospectively assessed. Cefiderocol trough concentration (Cmin) was determined at steady-state, and the free fraction (fCmin) was calculated according to a plasma protein binding of 58%. The fCmin/MIC ratio was selected as a pharmacodynamic parameter of cefiderocol efficacy and was defined as optimal if ≥4, quasi-optimal if between 1 and 4, and suboptimal if