by Michael Neilson, Pharmaceuticals Department Manager, BS, RM(NRCM), CQPA
Hard surface disinfectants go through a series of tests outlined in the AOAC International standard in order to be classified
as bactericidal, fungicidal, tuberculocidal, virucidal or sporicidal. Although the AOAC tests hold disinfectants to a high standard for determining efficacy against microorganisms, they are limited in the fact that they do not simulate real use conditions. It is therefore crucial that manufacturers who use these products to disinfect clean rooms and other controlled manufacturing environments, perform validation studies that support their in-house disinfection program.
Guidelines for performing disinfectant validations can be found in USP chapter <1072> entitled “Disinfectants and Antiseptics.” Validation studies are conducted based on several variables which include: surfaces found in the environment (stainless steel, glass, epoxy, etc.), organisms of key concern, disinfectants used, application methods and disinfectant exposure intervals.
The test procedure is a scaled down simulation of the in-house disinfection process. Test surfaces (coupons) are cut to approximately 2” x 2” in size. The coupons are inoculated with the test organism which is spread over a 1” x 1” area and allowed to dry. The inoculated coupons are then disinfected following the client’s application methods. Typically, coupons are left saturated for a pre-determined exposure time before they are assayed.
The assay procedure consists of transferring the disinfected coupon to a neutralizing broth that inactivates the antimicrobial action of the disinfectant. Viable organisms are then extracted through a manual shaking technique and appropriate aliquots are plated for recovery. Test coupon recoveries are compared to positive controls (inoculated, non-disinfected coupons) to determine the efficacy of the disinfectant.
The USP specifies that hard surface disinfectant regimens demonstrate a 3 Log10 reduction for vegetative bacteria and a 2 Log10 reduction for bacterial spores. By validating manufacturers’ disinfection programs, we help them to stay compliant with these regulatory expectations.