Electrochemically Synthesized Silver Nanoparticles Are Active Against Planktonic and Biofilm Cells of Pseudomonas aeruginosa and Other Cystic Fibrosis-Associated Bacterial Pathogens

Abstract

A novel, electrochemically synthesized, silver nanoparticles (AgNPs) formulation was evaluated <i>in vitro</i> against <i>Pseudomonas aeruginosa</i>, <i>Burkholderia cepacia</i>, <i>Stenotrophomonas maltophilia</i>, and <i>Staphylococcus aureus</i> strains from cystic fibrosis (CF) patients. AgNPs were particularly active against <i>P. aeruginosa</i> and <i>B. cepacia</i> planktonic cells (median MIC: 1.06 and 2.12 μg/ml, respectively) by a rapid, bactericidal and concentration-dependent effect. AgNPs showed to be particularly effective against <i>P. aeruginosa</i> and <i>S. aureus</i> biofilm causing a viability reduction ranging from 50% (1×MIC) to >99.9% (4×MIC). Electron microscopy showed that AgNPs deconstruct extracellular matrix of <i>P. aeruginosa</i> biofilm, and accumulate at the cell surface causing cell death secondary to membrane damage. Compared to Tobramycin, AgNPs showed comparable, or even better, activity against planktonic and biofilm <i>P. aeruginosa</i> cells. AgNPs at concentrations effective against <i>B. cepacia</i> and <i>P</i>. <i>aeruginosa</i> were not toxic to <i>G. mellonella</i> larvae. Our silver-based formulation might be an alternative to antibiotics in CF patients. Further <i>in vitro</i> and <i>in vivo</i> studies are warranted to confirm this therapeutic potential.