Determination of aztreonam/ceftazidime-avibactam synergism and proposal of a new methodology for the evaluation of susceptibility in vitro

Diagn Microbiol Infect Dis. 2024 Jun;109(2):116236. doi: 10.1016/j.diagmicrobio.2024.116236. Epub 2024 Mar 1.

Abstract

We proposed a new methodology, the microelution ATM/CZA (mATM/CZA), based on the antibiotic disc elution and the use of resazurin, for rapid (<4h) determination of in vitro susceptibility to aztreonam combined with ceftazidime-avibactam among Enterobacterales. The mATM/CZA presented excellent accuracy with 1.9 %, 98.1 % and 100 % of major error, specificity and sensitivity, respectively. Furthermore, we assessed synergism between aztreonam and ceftazidime-avibactam in Enterobacterales and Pseudomonas aeruginosa, which was observed in 37/55 Enterobacterales and 31/56 P. aeruginosa. As reference methodologies (checkerboard, time-kill curve) are not compatible with the routine of the clinical microbiology laboratories, mATM/CZA is an important alternative to evaluate susceptibility of the combination in a scenario where its clinical use is increasingly important.

Keywords: Aztreonam-avibactam; Ceftazidime-avibactam; Enterobacterales; Microelution ATM/CZA; P. aeruginosa; Synergism.

Publication types

  • Evaluation Study

MeSH terms

  • Anti-Bacterial Agents* / pharmacology
  • Azabicyclo Compounds* / pharmacology
  • Aztreonam* / pharmacology
  • Ceftazidime* / pharmacology
  • Drug Combinations*
  • Drug Synergism*
  • Enterobacteriaceae / drug effects
  • Humans
  • Microbial Sensitivity Tests* / methods
  • Microbial Sensitivity Tests* / standards
  • Oxazines
  • Pseudomonas aeruginosa / drug effects
  • Sensitivity and Specificity
  • Xanthenes

Substances

  • Aztreonam
  • Azabicyclo Compounds
  • Drug Combinations
  • Anti-Bacterial Agents
  • avibactam, ceftazidime drug combination
  • Ceftazidime
  • resazurin
  • Xanthenes
  • Oxazines