Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 1 2025 02 05 19 24 Arun Sachu Department of Microbiology, Believers Church Medical College, Thiruvalla, Kerala, India Alice David Head of Medical Research, Believers Church Medical College, Thiruvalla, Kerala, India 2024 07 08 2025 01 13 Background and Objectives: Carbapenem-resistant Enterobacteriaceae (CRE) infections are extremely difficult to treat and have a high fatality rate. The study's primary goal was to determine the rate of ceftazidime-avibactam susceptibility using disc diffusion and E-Test, as well as to evaluate the agreement between the two methods. Materials and Methods: A total of 124 multidrug-resistant (including carbapenem) Escherichia coli and Klebisella pneumoniae isolates were included. Kirby Bauer's disc diffusion and E-test were used as the testing methods in this study. Results: In this study 37.5% and 33.9% of the isolates were susceptible to ceftazidime-avibactam by E test and Disc diffusion respectively. There were five isolates which produced discordant results. Among the 56 isolates there was 91% agreement between the two methods. Conclusion: Among the discordant isolates the alarming disparity in zone size was a significant concern. Since CRE infections are very common, an economical and practical method for testing ceftazidime-avibactam susceptibility is needed in all the clinical microbiology laboratories as it is a last resort drug. https://ijm.tums.ac.ir/index.php/ijm/article/view/4901 https://ijm.tums.ac.ir/index.php/ijm/article/download/4901/1737