Qingxia Fu, Jingchun Kong, Shiyi Shi, Panjie Hu, Weiliang Zeng, Qing Wu, Tieli Zhou
This method is simple, rapid, and reliable, providing an intuitive approach for detecting AZA resistance-associated phenotypes in P. aeruginosa, with potential utility as a targeted screening approach in clinical microbiology laboratories.
OBJECTIVES: To develop and evaluate a rapid phenotypic method for detecting aztreonam-avibactam (AZA) resistance-associated phenotypes in Pseudomonas aeruginosa.
METHODS: Test isolates were incubated in medium containing fixed concentrations of AZA (aztreonam 20 µg/mL and avibactam 4 µg/mL). Resazurin was used as a redox indicator to monitor bacterial metabolic activity, with color change from blue to purple/pink indicating growth. The assay was evaluated using 103 clinical Pseudomonas aeruginosa isolates with different AZA MIC profiles, using broth microdilution as the reference method. Isolates were classified according to the EUCAST tentative ECOFF (TECOFF)-based epidemiological framework. Inter-assay reproducibility was assessed using independent assay runs.
RESULTS: The rapid NP test showed 100% agreement with the TECOFF-based WT/NWT classification derived from the reference broth microdilution method across all 103 clinical isolates. Consistent WT/NWT classifications were obtained across independent assay runs, supporting the inter-assay reproducibility of the method. The total turnaround time was 8 h.
CONCLUSION: This method is simple, rapid, and reliable, providing an intuitive approach for detecting AZA resistance-associated phenotypes in P. aeruginosa, with potential utility as a targeted screening approach in clinical microbiology laboratories.