AOAC Use-Dilution Test

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AOAC Use Dilution Test: Procedure at a Glance

For this study, bactericidal activity is measured qualitatively against various microorganisms.  Sterile test surfaces called penicylinders are inoculated with culture, dried, and then exposed to the test disinfectant at the label claim contact temperature and time.  The carriers are then transferred to neutralizing recovery medium, incubated, and observed for growth or no growth of the test organism.  A total of sixty (60) penicylinders, each with approximately 106 viable microorganisms, must be tested per lot of disinfectant. Three lots of the test disinfectant, each at the lowest certified level of active ingredient, must demonstrate between 54/60 and 59/60 carriers negative for growth for a passing result.  Organic soil may or may not be added to the test culture depending on the nature of the claim desired by the client.

Test controls are implemented into the study to account for any variables that could affect the test outcomes.  Test controls performed in the study are; assay of the concentration of the microbe used to inoculate the carriers,  measure the concentration of microorganisms as labeled onto the carriers, viability control of test medium, neutralization control, and media sterility.  The assay of the labeled carriers confirms the concentration is within the acceptable range, the viability control confirms media isn’t toxic to the test germs, neutralizing controls validates that the neutralizing recovery medium stops the bactericidal activity of the test disinfectant.

AOAC Use Dilution Test: Microchem’s Expertise

AOAC 955.14, 955.15, 964.02 (all variants of the AOAC Use Dilution) are run routinely by Microchem.  This study can also be customized to test additional microorganisms for more extensive and consumer directed label claims on the test disinfectant.  This test method is also utilized in the U.S. FDA  510K submission packet, those requirements are for only one lot of disinfectant against various microorganisms. The method is versatile, it can be used for various test chemistries (i.e. glutaraldehyde, ortho-phthalaldehyde, peracetic acide, hydrogen peroxide, phenol, and hypochlorous acid).

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