Antibacterial chelating agents with applications in industry and medicine: cellular metal restriction, membrane disruption and synergism with antibiotics in Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Bacillus subtilis and Staphylococcus aureus

Abstract

Aims: Chelating agents are metal sequestering compounds with antibacterial properties suitable for commercial and therapeutic applications. This study investigated the involvement of metal restriction and membrane disruption in the antibacterial mode of action of three chelators.

Methods and results: The antibacterial, metal sequestration and membrane disruptive effects of ethylenediaminetetraacetic acid, diethylenetriamine pentamethylene phosphonic acid and fusaric acid were examined across five bacterial species. ICP-MS was used to determine the impact on bacterial metal composition, while RT-qPCR of selected genes allowed evaluation of changes in cellular responses to intracellular metal depletion. Mutants defective in metal import and export machinery were also examined to validate processes critical for resistance. Chelator-mediated disruption of membranes was investigated using 1-N-phenylnapthylamine and propidium iodide. Finally, the capacity of two of the chelators to potentiate the activity of ampicillin, chloramphenicol, tetracycline and three aminoglycosides was assessed in checkerboards. The results show that these chelators restrict access to iron, zinc, manganese and calcium to varying degrees in these bacterial species, reflecting important differences in envelope architectures and metal handling capabilities.

Conclusions: This study shows that all three chelators behave differently in restricting metal access and possess antibacterial properties that often act synergistically in combination, notably with other antimicrobials.