Identification of carbapenemase genes and evaluation of in vitro activity of ceftazidime-avibactam against carbapenem-resistant Enterobacterales

Background: Infections caused by carbapenem-resistant Enterobacterales are becoming an intensifying global concern because of the scarce treatment options available. Carbapenem resistance plays a major role in increasing morbidity and mortality rates in healthcare settings. Ceftazidime-avibactam (CZA), demonstrates in vitro effectiveness against multi-drug resistant (MDR) organisms. The aim of the study was to identify various types of carbapenemase genes present among carbapenem-resistant Enterobacterales (CRE) and assess the in-vitro activity of ceftazidime-avibactam against carbapenem-resistant Enterobacterales. Material and Methods: This prospective study was carried out in the Microbiology section of the Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, from January to May 2024. Carbapenem-resistant Enterobacterales (CRE) isolated from blood cultures of patients were included in the study. The detection of carbapenem-resistant genes was conducted using the Xpert Carba-R assay. Antimicrobial susceptibility testing was performed using the Sensititre automated system. Results: During this period, sixty CRE isolates, recovered from blood culture samples were analysed. The most prevalent gene detected was NDM, found in 43 isolates (71.66%), followed by a combination of NDM and OXA-48 in 13 isolates (21.66%), and OXA-48 alone in 4 isolates (6.66%). Ceftazidime-avibactam (CZA) exhibited susceptibility in only 4 isolates (6.66%). All four of these isolates carried the OXA-48 gene alone. Conclusion: The study's findings indicated that, within the timeframe investigated, the NDM gene was the predominant resistant gene among CRE isolates, accounting for 93.33% of cases. Ceftazidime-avibactam demonstrated good activity against CRE isolates carrying the OXA-48 gene alone. However, it was not active against CRE isolates containing the NDM gene. Key Words: Carbapenem-resistant Enterobacterales, Carbapenemases, Ceftazidime-avibactam