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Antimicrobial Surface Validation Studies

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john_f_2_smallThere is a bewildering array of ISO and ASTM antimicrobial surface validation studies and a whole host of biocidal activity testing available. It can be very complex for companies to navigate their way through this and the results they get may not always translate into market valuable data. Control of indoor pathogens on surfaces and in the air is a highly topical issue, so we asked John Fallon PhD, Head of Microbiology at airmid healthgroup, to talk us through some of the testing we do at the laboratory and the relevance of this testing.

John, what exactly is an antimicrobial surface?
An antimicrobial surface is any surface with a chemical or physical treatment that inhibits or reduces the viability of bacterial or fungal microorganisms.

What is an antimicrobial surface validation study?
These studies are a set of experiments that aim to show the level of effectiveness of a bacteriostatic/fungistatic or bactericidal/fungicidal treatment of an antimicrobial surface.

What are the ISO tests you do at airmid for surface antimicrobial testing efficacy?
We do three main antimicrobial surface validation tests, ISO 27447:2009, which is for advanced technical ceramics but can also be adapted for glass and plastic; BS ISO 22196:2011, which is for plastics and other non-porous surfaces, and BS EN ISO 20743:2007 for textiles. To assess the effectiveness of fungistatic compounds in plastics formulations we use the BS ISO 16869:2008 test method. Finally ISO 27447:2009 is a test method used for the determination of the bactericidal efficacy of light activated treatments on ceramics, glass or plastics.

Tell us about the steps involved in the ISO 27447:2009 test
A pre-determined concentration of bacteria that has grown in a liquid solution overnight is placed onto the test surface, which has been treated with the antimicrobial coating, and also onto an untreated control. After a period of light exposure the number of viable bacteria that remain on the surface is quantified by initially washing and then plating out on a suitable agar. This is standardised against the recovery of bacteria at time zero and the recovery of bacteria from the untreated control surface. The data generated by this test is reproducible and enables the client to assess their product comprehensively in an objective and fact based manner. The test method commonly uses Escherichia coli and Staphylococcus aureus, however this can be adapted to include different microorganisms as specified by the client.

Can you modify these tests in any way to help with research and innovation?
The exposure time and the microoganisms used in the tests can be varied to meet the needs of the client.

Can you tell us about airmid healthgroup's expertise and experience in carrying out these tests?
We have a lot expertise in modifying the tests, such as varying the antimicrobial concentrations, changing the exposure times or the microorganisms under examination, and other modifications that can really help companies.

Further reading
Highly Effective Contact Antimicrobial Surfaces via Polymer Surface Modifiers P. Kurt, L. Wood, D.E. Ohman and K.J. Wynne - Langmuir, Volume 23, Issue 9, pages 4719 - 4723. (2007)

Polyethylene compounds with antimicrobial surface properties G. Seyfriedsberger, K. Rametsteiner and W. Kern. - European polymer journal, Volume 42, Issue 12, pages 3383 - 3389. (2006)