Suppression of β-Lactam Resistance by Aspergillomarasmine A is Influenced by Both the Metallo-β-Lactamase Target and the Antibiotic Partner

The rise of Gram-negative pathogens expressing metallo-β-lactamases (MBLs) is a growing concern, threatening the efficacy of β-lactam antibiotics, in particular, the carbapenems. There are no inhibitors of MBLs in current clinical use. Aspergillomarasmine A (AMA) is an MBL inhibitor isolated from Aspergillus versicolor with both in vitro and in vivo ability to rescue meropenem activity in MBL-producing bacteria. Here we systematically explored the pairing of AMA with six β-lactam antibiotic partners against nineteen MBLs from each subclass (B1, B2, B3). Cell-based assays with Escherichia coli and Klebsiella pneumoniae showed that bacteria producing NDM-1 and VIM-2 of subclass B1 were the most susceptible to AMA inhibition, whereas bacteria producing CphA2 and AIM-1 of subclasses B2 and B3, respectively, were the least sensitive. Intracellular antibiotic accumulation assays and in vitro enzyme assays demonstrated that the efficacy of AMA/β-lactam combinations did not correlate with outer membrane permeability or drug efflux. We determined that the optimal β-lactam partners for AMA are the carbapenem antibiotics, and the efficacy of AMA is linked to the Zn2+ affinity of specific MBLs.,Copyright © 2020 American Society for Microbiology.