Novel antimony-based antimicrobial drug targets membranes of Gram-positive and Gram-negative bacterial pathogens
Authors: Salpadoru Tarosha , Pinks Kevin E. , Lieberman Jacob A. , Cotton Kaitlyn , Wozniak Karen L. , Gerasimchuk Nikolay , Patrauchan Marianna A. 
Published: April 2024

Antimicrobial resistance (AMR) poses a significant worldwide public health crisis that continues to threaten our ability to successfully treat bacterial infections. With the decline in effectiveness of conventional antimicrobial therapies and the lack of new antibiotic pipelines, there is a renewed interest in exploring the potential of metal-based antimicrobial compounds. Antimony-based compounds with a long history of use in medicine have re-emerged as potential antimicrobial agents. We previously synthesized a series of novel organoantimony(V) compounds complexed with cyanoximates with a strong potential of antimicrobial activity against several AMR bacterial and fungal pathogens. Here, five selected compounds were studied for their antibacterial efficacy against three important bacterial pathogens:
Pseudomonas aeruginosa
,
Escherichia coli
, and
Staphylococcus aureus
. Among five tested compounds, SbPh
4
ACO showed antimicrobial activity against all three bacterial strains with the MIC of 50–100 µg/mL. The minimum bactericidal concentration/MIC values were less than or equal to 4 indicating that the effects of SbPh
4
ACO are bactericidal. Moreover, ultra-thin electron microscopy revealed that SbPh
4
ACO treatment caused membrane disruption in all three strains, which was further validated by increased membrane permeability. We also showed that SbPh
4
ACO acted synergistically with the antibiotics, polymyxin B and cefoxitin used to treat AMR strains of
P. aeruginosa
and
S. aureus
, respectively, and that at synergistic MIC concentration 12.5 µg/mL, its cytotoxicity against the cell lines, Hela, McCoy, and A549 dropped below the threshold. Overall, the results highlight the antimicrobial potential of novel antimony-based compound, SbPh
4
ACO, and its use as a potentiator of other antibiotics against both Gram-positive and Gram-negative bacterial pathogens.

IMPORTANCE

Antibiotic resistance presents a critical global public health crisis that threatens our ability to combat bacterial infections. In light of the declining efficacy of traditional antibiotics, the use of alternative solutions, such as metal-based antimicrobial compounds, has gained renewed interest. Based on the previously synthesized innovative organoantimony(V) compounds, we selected and further characterized the antibacterial efficacy of five of them against three important Gram-positive and Gram-negative bacterial pathogens. Among these compounds, SbPh
4
ACO showed broad-spectrum bactericidal activity, with membrane-disrupting effects against all three pathogens. Furthermore, we revealed the synergistic potential of SbPh
4
ACO when combined with antibiotics, such as cefoxitin, at concentrations that exert no cytotoxic effects tested on three mammalian cell lines. This study offers the first report on the mechanisms of action of novel antimony-based antimicrobial and presents the therapeutic potential of SbPh
4
ACO in combating both Gram-positive and Gram-negative bacterial pathogens while enhancing the efficacy of existing antibiotics.