ISO 22916 – Antimicrobial products – Test for antimicrobial activity and efficacy
Field of application:
The ISO 22916 test method was designed to test the antimicrobial activity/efficacy of plastics.
In 2007 the JIS Z 2801 method was internationally standardized as ISO 22196.
Sample requirements for ISO 22196:
The samples should habe a size of 5 x 5 cm.
At least 6 pieces of the blank samples are necessary for each measurement setup.
At least 3 pieces of the antimicrobially equipped samples are necessary for a measurement.
The surface of the samples should be plain/smooth.
Paints/colors/lacquers/coatings can be delivered as liquids. We will paint LENETA-test plates (as carriers) for the paints/colors/lacquers/coatings.
Please bag the samples and label them accordingly with the information which you wish to communicate in relation to the batch or series number or content of the sample.
Please never mark the sample with felt pens or markers!
Their colors run easily and as a result are often unsuitable. This is also true for permanent markers. If it is necessary to label the sample please use a pencil.
How does the ISO 22196 test method work?:
- the test microorganism is directly taken from agar plates and diluted in a buffer
- the concentration of the microorganism is standardized by dilution in a nutritive broth
- control and test surfaces are inoculated with 0.4 ml of the germ suspension in triplicate
- then the inoculum is covered with a film to prevent the evaporation of the suspension and to ensure close contact with the samples surface
- immediately after inoculation, the bacteria from the reference sample are separated from the sample surfaces and the number of viable germs is determined (t0 value) by elution followed by dilution and plating
- the others samples (t24) are allowed to incubate in a humid environment for 24 hours
- after incubation, microbial concentrations on are determinedby elution followed by dilution and plating
- activity/efficacy is calculated by comparing the germ concentration after 24 hours relative to concentration of the blank sample after 24 hours
Strengths of the ISO 22196 test method:
- reproducibility and repeatability are satisfactory (the ISO says at least 60% variance)
Weaknesses of the ISO 22196 test method:
- not really suitable for hydrophobic samples
- according to the norm the samples have to be quite big: 5 x 5 cm
- the sample surface has to be plain and smooth
- curved samples are just partly suitable
- quite average/low sensitivity