<p>Preparation of a series of ten 3-arylcoumarin molecules, their respective <i>fac</i>-[Re(CO)<sub>3</sub>(bpy)L]<sup>+</sup>
and <i>fac</i>-[Re(CO)<sub>3</sub>(L⁀L)Br]
complexes. All compounds were tested for their antimicrobial efficacy. Whereas the 3-arylcoumarin ligands are virtually inactive against the human-associated pathogens
with minimum inhibitory concentrations (MICs)
> 150 µM, when coordinated to the <i>fac</i>-[Re(CO)<sub>3</sub>]<sup>+ </sup>core,
most of the resulting complexes showed remarkable antibacterial potency<i>. </i>Several rhenium complexes exhibit activity in
nanomolar concentrations against Gram-positive pathogens such as <i>Staphylococcus aureus</i> strains, including
methicillin-resistant <i>S. aureus</i>
(MRSA) and <i>Enterococcus
faecium</i>. The molecules do not affect bacterial
cell membrane potential, but some of the most potent complexes strongly
interact with DNA, indicating it as a possible target for their mode of action.
<i>I</i><i>n vivo </i>studies in the zebrafish
model showed that the complexes with anti-staphylococcal/MRSA activity were non-toxic
to the organism even at much higher doses of the corresponding MICs. In the
zebrafish-MRSA infection model, the complexes increased the survival rate of infected
fish up to 100 % and markedly reduced bacterial burden. Moreover, all rescued
fish developed normally following the treatments with the metallic compounds.</p>