Disinfectant Efficacy Studies and their role in Cleaning and Monitoring Programs

Establishing the effectiveness of disinfectants is an important component of a facility cleaning and environmental monitoring program. The variables related to disinfection of surfaces, along with the time and labor required to conduct these studies, can make them complex. Differences between disinfectant efficacy studies and a materials cleaning validation can lead to confusion over the best and most cost-effective approaches to take with each.

How do cleaning validation and disinfectant efficacy differ?

Cleaning validation studies are conducted to show that the cleaning process and frequency, including any mechanical cleaning actions, are sufficient to maintain surfaces in a defined state free of product, cleaning chemical residues and microbes. These studies demonstrate that materials can be cleaned to the desired chemical and microbiological levels. A disinfectant efficacy study focuses on how well selected disinfectants reduce or eliminate microorganisms on surfaces to which they are applied. Disinfectant studies support cleaning studies by showing that application of the disinfectant reduces or eliminates microorganisms. They are not a substitute for cleaning validation studies.

How are disinfectant efficacy studies performed?

The most basic and inexpensive way to evaluate disinfectant effectiveness is to spike target microorganisms directly into tubes containing the disinfectant and determine the population reduction at various exposure times. Though easy and relatively quick to perform, the results may not reflect actual efficacy of the disinfectants against microorganisms on surfaces in the facility. A better method is to fix the microrganism onto hard, non-porous surfaces typically disinfected at a facility, such as stainless steel, glass, countertop and floor materials. Small “coupons” of each surface type are used. Following exposure of inoculated coupons to the disinfectants for a specified time, the reaction is neutralized, and remaining viable microorganisms are recovered. Effectiveness is determined by comparing the microorganism population killed, expressed as log reduction, to controls representing the population remaining on unexposed surface coupons.

Careful selection of representative surfaces and challenge microorganisms is required for a meaningful disinfectant efficacy study. Depending on the effectiveness of cleaning procedures in the facility or products used in the facility, the introduction of soils onto the surface coupons may be necessary to mimic actual conditions more closely.

Preliminary testing includes neutralization of the anticipated disinfectant residue, demonstration that microorganisms are not inhibited by the neutralizer, and use of established recovery methods to remove and enumerate the microorganisms from surfaces. For virus studies, laboratories must also evaluate cytotoxicity on indicator cells and interference of the neutralized disinfectant on the ability of the cells to grow the virus. Controls run during each phase ensure that the results can be adequately evaluated and subsequent testing is valid.

Study timelines

The importance of planning for disinfectant efficacy studies cannot be over-emphasized. The studies can be labor-intensive and take several months to evaluate multiple disinfectants and multiple timepoints with various microorganisms on different surfaces.

What organisms are used in disinfectant studies?

Disinfectant challenges with bacteria, yeast and molds are the most common studies conducted. Where facilities or operations must control and remove virus or mycoplasma, these target microorganisms must also be evaluated.

Eurofins Lancaster Laboratories has extensive experience in the design and execution of disinfectant efficacy and cleaning validation studies. Contact Bio/Pharmaceutical Business Development at 717-656-2300 to discuss your project needs.