Transcriptomic analysis of the activity and mechanism of action of a ruthenium(II)-based antimicrobial that induces minimal evolution of pathogen resistance

Increasing concern over rising levels of antibiotic resistance among pathogenic bacteria has prompted significant research into developing efficacious alternatives to antibiotic treatment. Previously, we have reported on the therapeutic activity of a dinuclear ruthenium(II) complex against pathogenic, multi-drug-resistant bacterial pathogens. Herein, we report that the solubility properties of this lead are comparable to those exhibited by orally available therapeutics that in comparison to clinically relevant antibiotics it induces very slow evolution of resistance in the uropathogenic, therapeutically resistant, E. coli strain EC958, and this resistance was lost when exposure to the compound was temporarily removed. With the aim of further investigating the mechanism of action of this compound, the regulation of nine target genes relating to the membrane, DNA damage, and other stress responses provoked by exposure to the compound was also studied. This analysis confirmed that the compound causes a significant transcriptional downregulation of genes involved in membrane transport and the tricarboxylic acid cycle. By contrast, expression of the chaperone protein-coding gene, spy, was significantly increased suggesting a requirement for repair of damaged proteins in the region of the outer membrane. The complex was also found to display activity comparable to that in E. coli in a range of other therapeutically relevant Gram-negative pathogens.