Development of a Whole-Cell Biosensor for β-Lactamase Inhibitor Discovery

ABSTRACT The clinical utility of the β-lactam antibiotics has been endangered by the production of β-lactamases by β-lactam-resistant pathogenic bacteria such as Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii . Collectively, these enzymes can degrade every clinically available β-lactam, jeopardizing antimicrobial therapy. Although extensive efforts have been made to develop β-lactamase inhibitors, inhibitor-resistant β-lactamases emerge rapidly. In addition, there are currently no clinically available inhibitors against the metallo-β-lactamases, a group of β-lactamases of great global concern. To further inhibitor discovery efforts, new assays are required to assess inhibitor efficacy, particularly in a cellular context. We report the development of a whole-cell E. coli biosensor which can quantify β-lactamase inhibition in a cellular context. Upon administration of an effective inhibitor, a β-lactam is rescued from β- lactamase-catalyzed degradation, resulting in the emission of a luminescent signal by the biosensor. This platform was validated using a panel of clinically relevant β-lactamases and was applied to quantitatively study the potency of a selection of currently used and reported β-lactamase inhibitors. This rapid method can account for factors like membrane permeability and can be employed to identify new β-lactamase inhibitors.