Bacterial resistance to silver nanoparticles and how to overcome it


Silver nanoparticles have already been successfully applied in various biomedical and antimicrobial technologies and products used in everyday life. Although bacterial resistance to antibiotics has been extensively discussed in the literature, the possible development of resistance to silver nanoparticles has not been fully explored. We report that the Gram-negative bacteria Escherichia coli 013, Pseudomonas aeruginosa CCM 3955 and E. coli CCM 3954 can develop resistance to silver nanoparticles after repeated exposure. The resistance stems from the production of the adhesive flagellum protein flagellin, which triggers the aggregation of the nanoparticles. This resistance evolves without any genetic changes; only phenotypic change is needed to reduce the nanoparticles’ colloidal stability and thus eliminate their antibacterial activity. The resistance mechanism cannot be overcome by additional stabilization of silver nanoparticles using surfactants or polymers. It is, however, strongly suppressed by inhibiting flagellin production with pomegranate rind extract.

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Fig. 1: Gradual aggregation and precipitation of silver NPs in microplates containing ‘Ag-resistant’ E. coli CCM 3954 after 0, 4, 8, 12, 16 and 24 hours of cultivation.
Fig. 2: High aggregation stability of silver NPs after culturing with ‘Ag-susceptible’ bacteria demonstrated by TEM images.
Fig. 3: UV/Vis absorption spectra.
Fig. 4: Effect of adding flagellin.
Fig. 5: Chemical mapping analysis of silver aggregates in presence of bacteria.


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We acknowledge the support provided by projects LO1305 and LM2015073 of the Ministry of Education, Youth and Sports of the Czech Republic, the Czech Science Foundation (project no.15–22248S), the Ministry of Health of the Czech Republic (AZV VES 15-27726A) and the Internal Grants of Palacký University in Olomouc (IGA_PrF_2015_022 and IGA_LF_2016_022).

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A.P. and L.K. conceived the project and designed the experiments dealing with synthesis of silver NPs. M.S. and R.P. carried out the experiments dealing with synthesis and stabilizations of silver NPs including their characterizations. R.V. and M.K. designed and carried out the microbiological experiments. M.R. carried out the experiments dealing with genomic analysis. F.D. and M.S. carried out the experiments dealing with proteomic analysis and viability tests. O.T. was responsible for HRTEM characterizations. R.Z. contributed clarifications and guidance on the manuscript. A.P. and R.Z. wrote the paper with input from all co-authors.

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Correspondence to Libor Kvítek or Radek Zbořil.

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Panáček, A., Kvítek, L., Smékalová, M. et al. Bacterial resistance to silver nanoparticles and how to overcome it. Nature Nanotech 13, 65–71 (2018).

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