Evaluation of the sensitivity pattern of ceftazidime-avibactam against multidrug-resistant gram-negative Isolates of Enterobacterales
Abstract
Objectives: Surveillance of antimicrobial susceptibility patterns is essential for guiding effective therapy. This study aimed to evaluate the in vitro activity of ceftazidime-avibactam against Enterobacterales stratified by resistance phenotype. Material and Methods: This retrospective, laboratory-based surveillance study was conducted from 1st February to 30th November 2023 at the National Institute of Cardiovascular Diseases, a tertiary care cardiac centre in Karachi, Pakistan. We analysed 236 non-duplicate Enterobacterales isolates obtained from 98 blood and 138 respiratory specimens. Antimicrobial susceptibility testing was performed according to Clinical and Laboratory Standards Institute guidelines. Associations between resistance phenotype and ceftazidime-avibactam susceptibility were assessed using the Chi-square test, Cramér’s V, linear-by-linear association, and odds ratios with 95% confidence intervals. Results: Overall, 179/236 (75.8%; 95% CI: 70.0–80.9) isolates were susceptible, and 57/236 (24.2%; 95% CI: 19.1–30.0) were resistant to ceftazidime-avibactam. Among blood isolates, susceptibility declined from 95.0% in non-Multidrug resistant organisms (non-MDRO) to 30.3% in carbapenem-resistant Enterobacterales (CRE) isolates (χ² = 32.08, p < 0.001). Respiratory isolates showed a similar decrease from 97.1% to 34.5% (χ² = 55.83, p < 0.001). Significant linear trends of decreasing susceptibility across resistance phenotypes were observed in both specimen groups. CRE isolates had significantly higher odds of resistance than ESBL producers. Conclusion: Ceftazidime-avibactam demonstrated high activity against non-MDRO and ESBL-producing Enterobacterales but reduced efficacy against CRE isolates, with susceptibility declining progressively across resistance phenotypes in both blood and respiratory specimens. Keywords: Beta-lactamase inhibitors, Carbapenem-resistant enterobacteriaceae, Ceftazidime, Drug resistance, Microbial, Sensitivity test