Can disc diffusion susceptibility tests assess the antimicrobial activity of engineered nanoparticles?

Angeliki Kourmouli, Marco Valenti, Erwin van Rijn, Hubertus J.E. Beaumont, Olga Ioanna Kalantzi, Andreas Schmidt-Ott, George Biskos*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

57 Citations (Scopus)
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The use of disc diffusion susceptibility tests to determine the antibacterial activity of engineered nanoparticles (ENPs) is questionable because their low diffusivity practically prevents them from penetrating through the culture media. In this study, we investigate the ability of such a test, namely the Kirby-Bauer disc diffusion test, to determine the antimicrobial activity of Au and Ag ENPs having diameters from 10 to 40 nm on Escherichia coli cultures. As anticipated, the tests did not show any antibacterial effects of Au nanoparticles (NPs) as a result of their negligible diffusivity through the culture media. Ag NPs on the other hand exhibited a strong antimicrobial activity that was independent of their size. Considering that Ag, in contrast to Au, dissolves upon oxidation and dilution in aqueous solutions, the apparent antibacterial behavior of Ag NPs is attributed to the ions they release. The Kirby-Bauer method, and other similar tests, can therefore be employed to probe the antimicrobial activity of ENPs related to their ability to release ions rather than to their unique size-dependent properties. [Figure not available: see fulltext.].

Original languageEnglish
Article number62
Number of pages6
JournalJournal of Nanoparticle Research: an interdisciplinary forum for nanoscale science and technology
Issue number3
Publication statusPublished - 2018


  • Aerosol-based nanoparticle synthesis
  • Antimicrobial activity
  • Disc diffusion method
  • Engineered nanoparticles
  • Gold nanoparticles
  • Silver nanoparticles


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