Silver i-motifs and their antibacterial activity

The spread of antibiotic resistance and the emergence of multi-drug resistant bacteria is a major threat to public health. This study investigated a unique cytosine rich DNA structure, the i-Motif to deliver soluble Ag+ as a novel antimicrobial agent (AgiMs). AgiMs were evaluated in vitro against P. aeruginosa and A. baumannii strains. AgiMs displayed significant antibacterial activity against both P. aeruginosa and A. baumannii (median MIC: 0.875 µM and 0.75 µM, respectively) by rapid, bactericidal and concentration-dependent effect. Low concentrations of AgiMs showed efficacy against PAO1 20-h biofilms, resulting in 57% reduction in biomass (5 x MIC). A single dose of AgiMs extended survival of G. Mellonella larvae, with the therapeutic benefit paralleled in the reduction of internal bacterial load. Synergistic interactions were observed with the combination of AgiMs and tobramycin, a common antibiotic used to treat P. aeruginosa infections; indicating the potential for AgiMs to reinstate the potency of current antibiotics. This silver-based agent might be an alternative to the failing antibiotic regimes for MDR resistant infections. Further in vitro and in vivo studies are warranted to confirm the therapeutic potential.