EPA Disinfectant Towelette Test

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EPA Towelette Test: Procedure at a glance

The typical bacteria used in this test, S. aureus, P. aeruginosa, and S. enterica are representative Gram-positive and Gram-negative pathogenic bacteria. The microorganisms are inoculated and dried onto the surface of glass microscope slides, the carrier. The slides are then wiped with pre-saturated disinfectant towelettes, held for a pre-determined amount of time, transferred to neutralizing recovery medium, and then incubated for 48 ± 4 hours. The EPA performance criterion for disinfection for a 60 carrier test allows 1 or fewer positive carriers for growth with a microorganism. Bactericidal activity is measured qualitatively against various microorganisms. This method requires there be an organic soil load present in the germ culture used to label carriers. Sterile carriers, glass microscope slides, are sterilized prior to use, inoculated with culture, and dried. The carriers are then exposed to the test disinfectant towelette through a wiping motion at the label claim contact temperature and time. The carriers are then aseptically transferred to neutralizing recovery medium, incubated, and observed for growth or no growth of the test germ. A total of sixty (60) carriers, with approximately 105 colony forming units of the test germ, must be tested per lot of disinfectant. Three lots of the test disinfectant, one lot must be at least 60 days old, must demonstrate 59/60 carriers negative for growth of the test germ. A total of sixty (60) carriers will test per lot of disinfectant per test germ.

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 germ used to inoculate the carriers, measure the concentration of the germ 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 is not toxic to the test germs,and the neutralizing controls validates that the neutralizing recovery medium stops the bactericidal activity of the test disinfectant.

EPA Towelette Test: Microchem’s Expertise

Germicidal Towelette Method/AOAC Official Method 961.02- is a modification of the AOAC Germicidal Spray Products as Disinfectants Test 961.02 for pre-saturated towelettes, alternatively to spraying a contaminated test surface, this method uses a wiping motion. The EPA requires that 60 carriers are tested against various microorganisms for three different batches/lots of disinfectant. The magnitude of the test can be minimized to ten carriers for preliminary study and the performance criterion allows 0 positive carriers for growth with an microorganism.

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