Disinfectant efficacy studies, as outlined in USP <1072>, are a formal evaluation of the effectiveness of a disinfectant against a set of specific microorganisms when applied to particular surfaces.  This type of study is essential to:

1. Assess the ability of the disinfectant to reduce or eliminate microbial populations on surfaces
2. Ensure that the disinfectant meets regulatory requirements
3. Provide data that supports the overall cleaning validation process and ensures that equipment and surfaces are free from harmful microorganisms

Studies of this nature are essential for validating the effectiveness of disinfectants used in various settings, including GMP pharmaceutical manufacturing facilities, hospitals, and laboratories.

What Information Needs to be Determined Before Starting a Disinfectant Efficacy Study

Before initiating a disinfectant efficacy study, there is a bit of information that needs to be determined. Namely, you would need to know:

1. The surfaces that the disinfectant will be used on;
2. The organisms that you wish to evaluate;
3. The disinfectants / cleaning agents you are looking to evaluate as well as their strength / concentration; and
4. The contact times of each disinfectant.

Studies are typically performed on a combination of standard reference organisms from entities like the ATCC, as well as some in-house organisms specific to the site being evaluated.

How Testing is Performed

There are three main phases to a disinfectant efficacy study. They are as follows:

1. Organisms Development
2. Neutralization Study
3. Surface Challenge Test / Disinfectant Efficacy Determination

Organism Development

Organism development studies are performed on microorganisms where historical data regarding optimal growth conditions is not available. This phase is generally required for any environmental isolates that are being evaluated. For common ATCC strains, this step may not be necessary if sufficient historical data from the testing facility is available.

Neutralization Study

Neutralization studies are used to verify that the method that will be used for the disinfectant efficacy work will be able to recover organisms. Specific neutralizers are chosen based on their ability to “quench” the disinfectant’s activity without being toxic to the microorganisms being tested. There are different approaches that can be utilized with dilution, washing, or specific chemical neutralizers being the most common.

At this phase, we are effectively validating that the neutralizer itself (which will stop the disinfecting “action” of a particular disinfectant), will not have its own effect on the microorganisms. This ensures that disinfectant efficacy results during the surface challenge tests are reliable.

Surface Challenge Test / Disinfectant Efficacy Determination

The final phase of the disinfectant efficacy study would be the surface challenge tests. This test phase is relatively straightforward and the following steps are followed:

1. Surface coupons, that are representative of the environment that the disinfectant will be used on, are inoculated with with known quantities of the test organism.
2. The specified disinfectant is prepared at the required concentration and applied for the specific contact time.
3. After the contact time, the disinfectant is neutralized, and organisms are recovered.

If the log reduction in viable organisms meets test requirements (this is usually a log reduction of 3 or more), the study is considered a success. If requirements are not met, portions of the study can be repeated using higher disinfectant concentrations or longer contact times.

Planning Your Disinfectant Efficacy Study

Disinfectant Efficacy Studies can be very time consuming. Small adjustments to the overall project plan can make enormous differences in how quickly and efficiently these studies are executed.

To ensure the best use of time, a sufficient number of surface coupons on a non-porous and autoclavable substrate should be made available to our testing facility. This will maximize the amount of time performing study activities.

At a minimum, for the disinfectant efficacy study, testing activities performed during the neutralization studies and surface challenge tests should be performed in triplicate to mitigate the appearance of any outliers. While microorganisms can grow very predictably, they are still biological systems and will be subject to some variability.

Conducting disinfectant efficacy studies is a vital component for maintaining a safe and compliant manufacturing, laboratory, and hospital environment. By following the guidelines outlined in USP <1072> and integrating these studies into a broader cleaning validation program, facilities can ensure that their disinfection protocols are effective and aligned with Good Manufacturing Practices (GMP).

For clients looking for disinfectant efficacy testing laboratory, Nucro-Technics is an excellent choice. Our organization bring more than 50 years worth of experience in the performance of these types of studies. With the largest microbiology laboratory in Canada, our organization has been performing thousands of microbiological tests to meet the needs of the pharmaceuticals industry since our founding in 1970.