Monitoring Ceftazidime-Avibactam (CAZ-AVI) and Aztreonam (ATM) Concentrations in the Treatment of a Bloodstream Infection Caused by a Multidrug-Resistant Enterobacter sp. Carrying both KPC-4 and NDM-1 Carbapenemases.

We report a sentinel occurrence of an infection with an Enterobacter sp. isolate producing KPC-4 and NDM-1 in the US. Recognition of the molecular basis of carbapenem resistance allowed for successful treatment by combining CAZ-AVI and ATM. Antimicrobial synergy testing and therapeutic drug monitoring allowed for assessment of treatment adequacy.