Disinfectant efficacy testing (DET) is a crucial component of any medical device manufacturing operation. Medical devices are only effective if they can perform their intended functions safely, and safe performance starts with reducing bioburden.

DET is a quality control measure that helps organizations validate the efficacy of their cleaning processes. It is designed to challenge a facility’s cleaning regimen to ensure that bacterial and fungal pathogens are being reduced to acceptable levels.

The process requires analyzing 2-inch by 2-inch material slides (i.e., coupons) taken from surfaces within facilities to understand the organisms present and validate that, if effective, the disinfectants and protocols in place promote a safe environment. Consistent environmental monitoring is essential for facilities that experience dramatic seasonal changes—new seasons mean new pathogens and new transfer methods.

Regular environmental monitoring is not only recommended, the U.S. Food and Drug Administration (FDA) mandates it. Regulatory bodies frequently audit facilities to ensure they have evidence of adequate controls over their environmental conditions and to ensure proper conditions for operations. Facilities that have recently expanded, changed locations, or switched to new disinfectant products are particularly susceptible to non-compliance.

There is no way to achieve 100 percent sterilization. If organizations are seeing frequent excursions, reevaluation of the entire cleaning process may be necessary. Still, DET can validate that facilities are using the right amounts of the right disinfectants for the proper periods of time to achieve the safest results.

How DET Works
DET starts with material coupons. Researchers inoculate the coupons with challenge organisms (i.e., bacteria, spores, fungus, etc.) and then subject them to a predetermined cleaning process. The test laboratory mimics the original facility’s wiping, mopping, spraying, and contact duration of the products used during real-world cleaning procedures. They then extract the coupons and measure the number of challenge organisms that remain.

At this point, researchers measure log reduction, or how thoroughly a decontamination process reduces the population of each challenge organism utilized. The test objective is to achieve a two- or three-log reduction of pathogens after subjecting coupons to the disinfection process. A two-log reduction means the process removed 99 percent of pathogens; three-log means 99.9 percent are gone. Spores and fungi require a two-log reduction, while vegetative bacteria require a three-log reduction.

Put simply, DET will determine if a facility’s cleaning regimen is killing problematic organisms in its environment. Between testing for organisms, utilizing facility-specific environmental isolates, running a neutralization validation, conducting efficacy checks, and allowing for a recovery step, the DET process can be complicated and time-intensive. When it comes to understanding current regulatory requirements and deciphering insights from previous testing, the advantages of partnering with an experienced laboratory partner become clear.

How to Avoid DET Pitfalls
Surface type, contact time, organisms present, disinfecting action, and hold times can all impact DET results. Any time one of these variables is altered, adjusted or overlooked, previous DET results may be affected or become invalid altogether. As combinations increase, DET studies become larger and more complex.

It may be tempting for organizations to try to save time and money on DET by combining testing for various locations. However, this approach is fundamentally flawed. Each site will have its unique variables that will impact DET and applying results haphazardly can lead to regulatory non-compliance. A more efficient and accurate approach is to send coupons and organisms from each location and, if necessary, prioritize the most critical ones. Then, after the initial round of testing, proceed with the following location and so on.

If a manufacturer has discovered a new or unexpected organism during testing, they can have it identified and held for later testing. Legacy knowledge of a particular facility is another instance in which a lab partner can be helpful. An external lab will often have the capacity to deal with new organisms and the ability to run tests on them in the future. Either way, organizations need to make sure someone is consistently monitoring organisms within the local environment to limit surprise variables during subsequent DET efforts.

A facility that does not achieve the log reduction it needs for certain combinations may need to alter its cleaning regimen. When sanitizer is left in contact with surfaces for too long, it can degrade and decline in efficacy. Sometimes facilities also try to speed up the disinfectant process by reducing the specified contact time. But too short a contact time on a surface can also reduce a sanitizer’s efficacy. Other mitigating factors include the humidity and temperature of the facility. Drastic fluctuations in either can influence the type and number of organisms present and impact a disinfectant’s effectiveness in day-to-day use.

Companies can also ensure successful DET results by being proactive, especially if they build new facilities or expand existing ones. Any change in infrastructure can bring new surfaces and new variables, so it is vital to arrange DET as soon as those variables are known. New facilities will not have the environmental monitoring data needed to identify the common pathogens found in their critical areas, but a laboratory testing partner should be able to use stock isolates and supplement with actual data using those site-specific isolates later.

Advice for Organizations Undergoing DET
It is essential to keep in mind that the main objective of DET is patient and staff safety—it is the goal of both medical device manufacturers and regulatory bodies alike. Therefore, the more thoroughly an organization prepares for DET, the greater the likelihood of successful testing and safe products. An experienced laboratory testing partner can help validate expanded or evolved cleaning processes and write new protocols that reflect emerging regulatory guidance.

DET should be considered a valuable tool to help organizations ensure their disinfectant processes are as safe and effective as possible while also meeting regulatory standards. Whether disinfectant protocols are conducted in-house or validated by a laboratory testing partner, the same guiding principles should be followed: plan ahead, be methodical, follow appropriate testing protocols, and maintain consistency. These factors can be critical to successful testing, contribute to overall productivity and ensure patient and staff safety. 

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Leslie Tavares is a manager of the Microbial Solutions Lab and Custom Studies Group at WuXi AppTec. 

Melinda Johnson and Jessica Lawrence are technical specialists with the Technical Services Group at WuXi AppTec. They regularly consult with customers on cleaning and disinfectant protocols.