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

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