ISO 7581:2023

Antimicrobial Testing (Non-Porous in a Dry Environment)

ISO 7581 is a standardised test method used for determining bactericidal activity of non-porous surfaces in a dry environment. Unlike other antibacterial test methods, ISO 7581 is a lot more stringent in its test conditions and is done so to replicate real-world use of antibacterial surfaces.

The ISO 7581:2023 procedure & assessment

BioLabTests offers ISO 7581 testing against E. hirae and S. aureus*. The method involves suspending bacteria in a nutrient broth and inoculating them onto samples surfaces before letting this inoculum dry out.

Untreated control samples are used as a comparative tool to determine how much bacteria are killed by a treated surface over a period of 1-2 hours contact. Whilst the bacteria are in contact with the sample surfaces, they are kept at 20°C, in ambient light and at a relative humidity of between 30-65%. These conditions are all to simulate real-world conditions that treated products may face on a daily basis.

1. specimen preparation & Incubation

Treated and untreated samples are placed into petri dishes before being inoculated with bacterial suspensions. The suspensions are then allowed to dry.

2. incubation

After the inoculum has dried, the samples are incubated for between 1 and 2 hours. Incubation is done at 20°C at a relative humidity of between 30% and 65%

3. recovery

After the allotted contact time, sample surfaces are washed off and any remaining bacteria are recovered and plated onto agar.

4. reading and results

After 48 hours incubation at 35-38°C, colonies of bacteria are counted on agar plates which allows us to quantitatively measure the bactericidal performance of the treated samples. Products can be considered as bactericidal when tested to ISO 7581 if they achieve at least 2 log reduction (99%).

These steps allow us to establish if an antibacterial product can be considered as bactericidal against the organisms tested.

*other organisms may be available upon request pending validation. Please note, we have found that this test method typically works better for Gram-positive organisms due to their increased ability to survive drying over their Gram-negative counterparts.

Things to note 

Credibility of result

The ISO 7581:2023 method is very newly published and as such has had no revisions as of yet. Internal validation at BioLabTests has shown the test working as intended for the organisms E. hirae and S. aureus. However, there are a further 2 organisms listed in the ISO 7581 method which have given inconsistent results in-house and we are therefore not offering at this time. These are E. coli and P. aeruginosa.

This test simulates real-world conditions and is more stringent than other industry standard tests like ISO 22196. We have therefore seen that it is more difficult for a treated sample to achieve positive results from this test. BioLabTests recommends that you ensure your product has a high level of antibacterial efficacy before submitting samples for this test.

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