Evaluation of gradient strip diffusion for susceptibility testing of aztreonam-avibactam in metallo-β-lactamase-producing Enterobacterales.

The emergence of metallo-β-lactamase (MBL)-producing Enterobacterales presents unique clinical treatment challenges. Recently developed β-lactam/ β-lactamase inhibitor combination agents, while effective against other carbapenemase-producing organisms, are notably ineffective against MBL producers. While MBLs do not hydrolyze monobactams (aztreonam), many MBL-producing organisms are resistant to aztreonam through alternate mechanisms, leaving cefiderocol as the sole monotherapy treatment option recommended for MBL producers.