Effect of silver nanoparticles on biofilms formation in Pseudomonas aeruginosa PAO1 and PA14

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Many studies have used biogenic silver nanoparticles as antibiofilm and antivirulence strategies to control the spread of multiresistant bacteria. The aim of this study was to evaluate the effect of subinhibitory concentrations of biogenic silver nanoparticles (bio-AgNP) on biofilm formation in Pseudomonas aeruginosa PAO1 and PA14 strains. Bio-AgNPs were synthesized by the fungus Fusarium oxysporum and the minimum inhibitory concentrations of the compound were determined by the microdilution method. The biofilms formation was evaluated by quantitative assay in polystyrene microtiter plates by the crystal violet method at 620 nm. Stock cultures of PAO1 and PA14 were maintained at -80 °C in Luria-Bertani broth with 20% glycerol. The minimum inhibitory concentration was 62.5 µM and subinhibitory concentrations (31.25, 15.62, and 7.81 µM) were selected for biofilm study. Assays were performed four times for each strain and the mean and standard deviation were determined. A p value < 0.05 was considered significant. The PAO1 and PA14 strains showed biofilm formation of 0.260 ± 0.040 and 0.052 ± 0.007, respectively. After treatment with bio-AgNPs at subinhibitory concentrations, there was no change in biofilm formation in P. aeruginosa PAO1. However, for PA14 there was a significant increase (p < 0.05) in biofilm formation after the three treatments, with increase rates ranging from 41.22 to 127.86%. The response to treatment with bio-AgNPs in the two strains was different, possibly because each isolate uses an exopolysaccharide as the predominant structural component in the biofilm. While strain PAO1 uses the Wsp system to produce the exopolysaccharide psl, strain PA14 uses the Pil-Chp system to produce the pel. Bio-AgNPs at subinhibitory concentrations showed an increase in biofilm formation in PA14 strain. Therefore, the use of bio-AgNPs for antibiofilm and antivirulence activities must be carefully evaluated. Since the presence of bio-AgNPs in low concentrations in the environment can promote an increase in the biofilms formation in bacterial isolates such as in P. aeruginosa.

  • 1 Núcleo de Ciências Químicas e Bromatológicas / Centro de Laboratório Regional de Presidente Prudente / Instituto Adolfo Lutz
  • 2 Centro de Laboratório Regional de Presidente Prudente / Instituto Adolfo Lutz / Instituto Adolfo Lutz
  • 3 Centro de Laboratório Regional de Bauru / Instituto Adolfo Lutz / Instituto Adolfo Lutz
  • 4 Departamento de Microbiologia / Centro de Ciências Biológicas / Universidade Estadual de Londrina
  • Microbiologia Médica Humana
Silver nanoparticles