Document Type

Article

Department

Pathology (East Africa)

Abstract

The combination of aztreonam and ceftazidime-avibactam is a proven treatment option for infections caused by metallo-beta-lactamase (MBL)-expressing gram-negative organisms. Restoration of aztreonam susceptibility in the presence of ceftazidime-avibactam can be determined using the Clinical and Laboratory Standards Institute (CLSI)’s broth disc elution (BDE) method; however, the high manual workload and significant material footprint of this assay make it difficult to implement in a high-throughput clinical microbiology lab. This study evaluates two agar-based methods for the detection of susceptibility to the combination of aztreonam and ceftazidime-avibactam, using BDE as the comparator methodology. Resistant Enterobacterales, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Acinetobacter spp. were selected, after which restoration of aztreonam susceptibility was tested using an E-test/disc diffusion (E-DD) method, a double-disc diffusion (DDD) method, and BDE. In comparison to BDE, both E-DD and DDD methods met CLSI M52 validation thresholds with respective categorical agreement rates of 93% and 96%, and no major (MDs) or very major discrepancies (VMDs). In conclusion, agar-based methods such as E-DD or DDD provide alternative methods to evaluate restoration of aztreonam susceptibility in the presence of ceftazidime-avibactam, which can subsequently be used to inform patient care decisions.

Publication (Name of Journal)

Microbiology spectrum

DOI

https://doi.org/10.1128/spectrum.03794-25

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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