ISO 22196:2011

Measurement of antibacterial activity on plastics and non-porous surfaces.

ISO 22196 specifies a method of evaluating the antibacterial activity of plastics enhanced with antibacterial properties and other non-porous surfaces of products (including intermediate products).

Test Conditions

The standard refers to the parameters to be observed when determining the bactericidal efficacy on plastics and other non-porous surfaces.  This includes the test microorganism, contact time and interfering substance.

• Test microorganism refers to the mandatory list of microbes that must be used in the test to determine the antimicrobial activity of the product. The mandatory microorganisms are assumed to represent all microbes in its group.
• Contact time refers to the minimum duration a product must remain in contact with the microbes for the product to be effective.

Test Method

The test requires at least 3 specimens from each treated test material and 6 specimens of untreated material. Half of the untreated test specimens are used to measure the viability of bacterial cells immediately after inoculation. The other half are used to measure the viability of bacterial cells after 24-hour period incubation.

First, the test specimens are prepared from the treated and untreated test materials. The specimens must be flat, 50 mm × 50 mm in size and no more than 10 mm thick. All the test specimens are placed in separate sterile petri dishes.

Next, the test surfaces are inoculated with 400 µl test inoculum (2.5 × 105 CFU/ml and 10 × 105 CFU/ml). The test inoculum is covered with a film measuring 40 mm x 40 mm and the petri dish closed with a lid.

The petri dishes containing the inoculated test specimens are incubated (including half of the untreated test specimens) at a temperature of 35 °C and relative humidity of not less than 90% for 24 hours.

Next, 10 ml of neutralizer is added to the petri dish. A 10-fold serial dilution is performed on the neutralizer and 10 ml of each dilution is plated with plate count agar. The plates are incubated at 35 °C for 40-48 hours.

Control Tests

For the control tests, untreated test materials are used as test specimens and placed in separate sterile petri dishes.

Next, the test surfaces are inoculated with 400 µl test inoculum (2.5 × 105 CFU/ml and 10 × 105 CFU/ml). The test inoculum is covered with a film measuring 40 mm x 40 mm.

Immediately after inoculation, process 3 of untreated test specimens by adding 10 ml of neutralizer to the Petri dish containing the test specimen.

A 10-fold serial dilution is performed on the neutralizer and 10 ml of each dilution is plated with plate count agar. The plates are incubated at 35 °C for 40-48 hours.

For the remaining 3 test specimens, the petri dishes containing the inoculated test specimens are closed with a lid and incubated at 35 °C and relative humidity of not less than 90% for 24 hours.

Next, 10 ml of neutralizer is added to the petri dish. A 10-fold serial dilution is performed on the neutralizer and 10 ml of each dilution is plated with plate count agar. The plates are incubated at 35 °C for 40-48 hours.

The log reduction is determined by comparing the bacterial count from treated and untreated test specimens.