Nicolau, David P.

ABSTRACT Carbapenem‐resistant Acinetobacter baumannii (CRAB) are difficult‐to‐treat pathogens that primarily cause health care‐associated infections. Sulbactam/durlobactam (SUL/DUR) is a novel antibiotic combination that is uniquely formulated to target CRAB isolates. However, investigations of SUL/DUR's pharmacokinetics in obese patients are limited. Here, we report on the successful treatment of CRAB bacteremia in a patient with acute renal failure and severe obesity (weight 273 kg, body mass index 103 kg/m 2 ) with SUL/DUR and meropenem combination therapy. The patient had a calculated creatinine clearance of 25 mL/min and received therapy with intravenous SUL/DUR 1 g/1 g every 8 h over 3 h in combination with intravenous meropenem 500 mg every 8 h to complete 14 days of therapy. Pharmacokinetic analysis revealed target attainment with prolonged half‐life ( T 1/2 ) and volume of distribution (Vd) of 35.3 h and 81.3 L for sulbactam and 30.5 h and 169.1 L for durlobactam, respectively. Susceptibility testing using the broth disk elution test did not show synergy between SUL/DUR and meropenem. No adverse effects were observed, and the patient achieved clinical cure without recurrence of A. baumannii infection.

Abstract Purpose A case of vancomycin enzyme immunoassay (EIA) interference confirmed by high-performance liquid chromatography (HPLC) is described. Summary Therapeutic drug monitoring is standard of practice in vancomycin dosing and monitoring in order to maximize the pharmacodynamic effects and minimize toxicity. After a 52-year-old woman received 5 doses of vancomycin, serum concentrations continued to rise for several days in the absence of ongoing vancomycin administration. Despite persistently elevated vancomycin concentrations, the patient clinically deteriorated and required treatment with an alternative agent. Subsequently, serum concentrations were processed via HPLC and analyzed for percent protein binding. Confirmatory analysis revealed substantially lower concentrations by HPLC than were obtained by EIA and an abnormal elevation in protein binding. After discharge from the index admission, the patient returned 11 months later and had a dectectable vancomycin concentration by EIA prior to receipt of vancomycin. HPLC analysis confirmed the true concentration was undetectable. Though the exact interfering substance was not identified, the above discrepancy in concentrations between the two assay methods indicates the presence of assay interference, and adds to the available literature suggesting similar occurrences. This case is particularly troubling given that the level of interference was not such that it would lead a clinician to immediately suspect interference, and the patient experienced treatment failure. Conclusion Falsely elevated values for serum vancomycin concentration, measured by EIA, contributed to treatment failure in a patient. The substance presumably responsible for EIA interferences was not identified.