An insight into Ceftazidime-avibactam activity on Carbapenem-resistant Enterobacterales causing bloodstream infections

Introduction: Carbapenem-resistant Enterobacterales (CRE) are among the biggest challenges faced by the healthcare community worldwide. Antibiotic treatment of these infections remains challenging, especially in developing nations. Ceftazidime-avibactam (CZA) is a β-lactam-β-lactamase inhibitor combination with potent activity against CRE. The present study was conducted to provide insight into the in vitro activity of CZA against CRE causing bloodstream infections. Methods: This was a prospective observational study, conducted from July 2022 to June 2023 at a tertiary care teaching hospital, Jaipur, and included all non-duplicate CRE isolates obtained from bloodstream infections in adult patients admitted to the ICU. Identification and antimicrobial susceptibility testing were performed using the VITEK-2 automated system and interpreted according to Clinical and Laboratory Standards Institute guidelines. All CRE isolates resistant to CZA were further tested for synergy between Ceftazidime-avibactam and Aztreonam (AT) using the disk elution method. Results: During the one-year study period, 104 CRE strains were isolated in the laboratory from bloodstream infections in adult patients admitted to the ICU, which included 19 (18%) E. coli, 80 (77%) K.pneumoniae and 5 (5%) Enterobacter spp. Susceptibility rates of 61%, 31% and, 30% were observed for amikacin, tigecycline and minocycline, respectively. Overall, 31% and, 4% CRE isolates were susceptible to CZA and AT alone, respectively, while 97% were found to exhibit synergy. Conclusion: In the present study, 69% CRE isolates were found to be resistant to CZA. CZA+ATM combination, however, demonstrated excellent in vitro activity against CRE isolated from blood cultures in our ICU setting. Thus, this combination can be considered a suitable therapeutic option in patients with sepsis.