In Vitro Discordance with In Vivo Activity: Humanized Exposures of Ceftazidime-Avibactam, Aztreonam, and Tigecycline Alone and in Combination against New Delhi Metallo-{beta}-Lactamase-Producing Klebsiella pneumoniae in a Murine Lung Infection Model [PublishAheadOfPrint]

The management of infections with New Delhi Metallo-beta-lactamase-1 (NDM) producing bacteria remains clinically challenging given the multi-drug resistant (MDR) phenotype associated with these bacteria. Despite resistance in vitro, ceftazidime-avibactam previously demonstrated in vivo activity against NDM+ Enterobacteriaceae. Herein, we observed in vitro synergy with ceftazidime-avibactam and aztreonam against a MDR K. pneumoniae harboring NDM. In vivo, humanized doses of ceftazidime-avibactam monotherapy resulted in > 2 log₁₀CFU bacterial reduction, therefore, no in vivo synergy was observed.

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