Rapid identification of carbapenemases and in vitro synergy testing of ceftazidime-avibactam with aztreonam in extensively drug-resistant gram-negative pathogens: Establishing the realm of promise

This study evaluated the effectiveness of ceftazidime-avibactam (CZA) alone and in combination with aztreonam (ATM) against 50 extensively drug-resistant (XDR) Gram-negative bacteria (GNB) isolates using disk stacking method. New Delhi metallo-beta-lactamase (NDM) was the predominant carbapenemase, detected in 50 % of isolates showing synergy. The CZA-ATM combination demonstrated synergy in 40 % of isolates, with 75 % of patients receiving this combination achieving microbiological clearance. This simple, rapid synergy testing method can guide effective therapeutic decisions in resource-limited settings.