ASTM E2362-22. Standard Practice for Evaluation of Pre-saturated or Impregnated Towelettes for Hard Surface Disinfection.

Test accredited by ENAC (Spanish National Accreditation Entity).

The ASTM E2362 Standard describes a test method for evaluating the antimicrobial efficacy of pre-saturated or impregnated wipes used to disinfect hard surfaces. This test provides a qualitative endpoint. Results are expressed as positive or negative growth of the test microorganism, and not as quantitative reductions of the test organisms.

In this test, a towelette pre-saturated or impregnated with a test substance is used to treat a 625 square mm surface of a non-porous glass carrier that has been inoculated with the test microorganisms. The test microorganisms indicated by the standard are: the bacteria Staphylococcus aureus, Salmonella enterica subsp. enterica and Pseudomonas aeruginosa; the mycobacterium Mycobacterium bovis; and the fungus Trichophyton interdigitale (from Trichophyton mentagrophytes complex). The standard indicates that other microorganisms can be tested using culture methods appropriate for them. Depending on the use of the product, an interfering substance will or will not be added to the test inoculum. If the test wipes are to be used for the disinfection of pre-cleaned surfaces, no interference substance should be added but, if the test wipes are intended to be used as disinfectants on soiled surfaces (without previous cleaning) blood serum, for example fetal bovine serum, or other appropriate interference substance, must be incorporated with the test inoculum. The carrier inoculated with the test microorganism and the interference substance, if applicable, is wiped with the towelette simulating the real application of the test substance and subsequently held for a pre-determined contact time, according to the conditions of use of the towelettes to be tested (according to the manufacturer instructions on the label). After the contact time, the carrier is transferred into a test tube containing a neutralizing subculture medium which neutralizes the remaining test substance and support growth of existing viable test microorganisms. It may be necessary to transfer the carrier to another tube with neutralizing medium to effectively neutralize the test substance. For mycobacteria, two tubes with neutralizing media per carrier and 2 additional subcultures from the second neutralizing media in two different broths are needed. All subcultures (excluding the first neutralizing tube for mycobacteria) are incubated for testing.

Subcultures are incubated for 48 hours at 36ºC ± 1ºC for bacteria, for 10 days at 27.5ºC ± 2.5ºC for fungi, and between 60 and 90 days at 36ºC ± 1ºC for mycobacteria. After this time, the liquid culture media should be observed to detect the presence of turbidity or growth typical for the test microorganism. Positive test carriers are examined by inoculation and incubation of the positive subcultures onto appropriate solid media for the test microorganism. The identification of test microorganisms should be verified by examining the morphology of the colonies and performing the Gram stain for bacteria. If necessary, other confirmation / identification techniques may be used.

The ASTM E2362 standard does not indicate the number of carriers to be used for the test with each microorganism, so the client must indicate the number of carriers to be tested. As guidance, the EPA MB-09-07 procedure, on which the ASTM E2362 test procedure is based, indicates that 60 test carriers are required per test bacteria. The EPA also states in the document Efficacy Testing Standards for Antimicrobial Product Data Call-In Responses (7/1/2015) that 60 carriers should be used for each bacterium and 20 carriers per microorganism for Trichophyton interdigitale (Trichophyton mentagrophytes complex) and Mycobacterium bovis. In the test report, the test results are reported as the number of carriers tested and the number of carriers positive for test microorganism per test substance.

The following information must be clearly indicated in the form to request the test: the tests microorganisms, the number of carriers requested per test microorganism, a detailed procedure for the application of the test substance with the pre-saturated or impregnated towelettes, the required contact time after application, and if the wipes will be used to disinfect clean or dirty surfaces. We recommend you consult any questions about the test to be performed with the relevant authorities where you will register your product. Unless otherwise indicated, IVAMI will follow the EPA instructions, performing the test with 60 carriers for each bacterium and 20 carriers for Trichophyton interdigitale (Trichophyton mentagrophytes complex) and Mycobacterium bovis.