Effect of colloidal
silver against Ciprofloxacin persisters of Pseudomonas aeruginosa PAO1
Braggs Carol and Desouza Anita
Res. J. Biotech.; Vol. 20(9); 134-151;
doi: https://doi.org/10.25303/209rjbt1340151; (2025)
Abstract
Pseudomonas aeruginosa causes chronic multidrugresistant infections, often linked
to antibiotic-tolerant persister cells in biofilms. The treatment of such infections
poses chemotherapeutic limitations. This study evaluates the efficacy of colloidal
silver (SilverSol® technology) against Ciprofloxacintolerant persisters of P. aeruginosa
PAO1 in planktonic and biofilm populations. Dose-kill assays showed persister formation
at 20×MIC of ciprofloxacin in planktonic cells and 50×MIC in biofilms. Colloidal
silver exhibited a MIC of 3ppm for planktonic cultures and 4 ppm for biofilm inhibition.
Complete eradication of Ciprofloxacin persisters occurred using colloidal silver
at 5×MIC in planktonic cells and 3×MIC in biofilms within 1 hour. Total biofilm
eradication was possible at 4 ppm using TTC viability assays. Checkerboard assay
revealed an additive effect of ciprofloxacin and colloidal silver (FIC index: 0.65).
FESEM imaging and Allison- Sutherland staining confirmed the absence of extracellular
matrix, demonstrating biofilm inhibition by the colloidal silver. Hence, these findings
highlight colloidal silver as a promising therapeutic strategy against persistent
infections caused by ESKAPE pathogens such as P. aeruginosa PAO1.
