TREATING CARBAPENEM-RESISTANT ENTEROBACTERALES INFECTIONS: SIGNIFICANCE OF COMBINING CEFTAZIDIME-AVIBACTAM WITH AZTREONAM IN INDIAN SCENARIO

Dr. Sreevalsan T. V.* and Dr. Rohitha S. Chandra

In Indian ICUs, carbapenem resistance is seen among a significant proportion of Gram-negative infections. In India, NDM and OXA-48 enzymes are the predominant carbapenemases unlike the Western countries where KPC is the commonest. As the MBLs including NDM are not inhibited by Avibactam, Ceftazidme- Avibactam (CAZ-AVI) will be of limited use in India. As Aztreonam (ATM) is not hydrolyzed by the NDM, combining it with CAZ-AVI can be effective in this context. This single centre retrospective study aimed to find out the susceptibility of CRE isolates to CAZ-AVI and the usefulness of combining it with ATM to treat CRE resistant to CAZ-AVI. 294 CRE isolates were tested from 30 May 2022 to 30 July 2023. Susceptibility to CZA-AVI, ATM was studied. Synergy of the combination of the two among the isolates resistant to CAZ-AVI was also studied. It was found that Klebsiella pneumoniae was the most common CRE. 56.12% of the CRE isolates were resistant individually to CAZ-AVI and ATM. However, 83% of these isolates were found to be sensitive on synergy testing. This pattern is suggestive of the presence of NDM along with OXA-48 among CREs as reported by other Indian studies. Since Ceftazidime-Avibactam as a monotherapy for CREs will likely result in clinical failure, susceptibility testing with CAZ-AVI and synergy testing with ATM should be used to guide the treatment of CRE infections.