Activity of ampicillin-sulbactam, sulbactam-durlobactam, and comparators against Acinetobacter baumannii-calcoaceticus complex strains isolated from respiratory and bloodstream sources: results from ACNBio study Article

Full Text via DOI: 10.1128/aac.00379-25 Web of Science: 001530906500001

Cited authors

  • Buyukyanbolu E, Argotsinger J, Beck ET, Chamberland RR, Clark AE, Daniels AR, Liesman R, Fisher M, Gialanella P, Hand J, Harrington AT, Humphries RM, Huse H, Hamilton-Seth R, Hankins JD, Kufel WD, Riddell SW, Marino J, Westblade LF, Mochon AB, Narayanan N, Kirn TJ, Pierce VM, Potula R, Tekle T, Simner PJ, Tibbetts RJ, Vu C, Abbo LM, Martinez O, Dumm RE, Nicolau DP, Asempa TE

Abstract

  • Infections caused by carbapenem-resistant Acinetobacter baumannii-calcoaceticus complex (ABC) are associated with high mortality rates and limited treatment options. This study aims to evaluate the in vitro activity of clinically utilized antimicrobials against a contemporary collection of ABC isolates with a predominant carbapenem-resistant phenotype. Geographically dispersed US medical centers (n = 22) provided non-duplicate respiratory and bloodstream ABC isolates for surveillance testing. Antimicrobial susceptibility testing was conducted by broth microdilution and interpreted according to Clinical & Laboratory Standards Institute (CLSI) and Food and Drug Administration (FDA) breakpoints. ABC isolates (n = 523) from respiratory tract (74.4%) and blood (25.6%) sources were recovered from patients (2023-2024). Forty percent were obtained from intensive care unit patients. Carbapenem non-susceptibility was observed in 76.9% of isolates and was more common among respiratory tract cultures. The addition of durlobactam to sulbactam decreased the MIC90 by three-doubling dilutions from 32 to 4 mu g/mL, increasing the susceptibility rate to 96.9% from 33.8%. Genome sequencing of sulbactam-durlobactam non-susceptible isolates (16/523; n = 3.1%) revealed MBL and non-enzymatic resistance mechanisms. Cefiderocol inhibited 93.5% and 76.1% of isolates at CLSI and FDA susceptible breakpoints, respectively. Minocycline susceptibility was <50%, while tigecycline and eravacycline MIC50/90 were 1/2 and 0.5/1 g/mL, respectively. Sulbactam-durlobactam displayed high activity against sulbactam (95.4%), carbapenem (96.3%), and cefiderocol (95.2%) non-susceptible isolates. Susceptibility rates of clinically utilized antimicrobials against a US collection of ABC isolates ranged from 23% to 97%, with meropenem displaying the lowest rate and sulbactam-durlobactam demonstrating the highest overall rate. Sulbactam-durlobactam activity was preserved against sulbactam, carbapenem, and cefiderocol non-susceptible isolates among respiratory tract and bloodstream isolates.

Authors

Publication date

  • 2025

Published in

International Standard Serial Number (ISSN)

  • 0066-4804

Number of pages

  • 10