Surgical instruments are not only a valuable asset for healthcare providers, but by their nature they are also a primary front from which facilities can fight infection. Proper handling, cleaning and storage of surgical instrumentation are crucial to protecting that investment and helping to ensure patient safety.
Cleaning, however, can be a challenge because of the variety of biological soils and the complicated configuration of surgical instruments. Soils, such as blood and tissue, can become trapped in pinch points and box locks. In addition, the type of soil can itself be difficult to remove; for example, fatty soils are difficult to penetrate while protein-based soils can adhere to instruments when dried. To ensure the adequate level of care and cleanliness of surgical instrumentation, it is very important to identify and qualify the suitable mechanical and chemical treatments.
Although instrument reprocessing procedures are evolving at a rapid pace, the removal of organic debris on medical devices continues to be an issue. Soil remaining on instruments after cleaning can cause the sterilization process to fail, therefore jeopardizing patient safety. The purpose of this article is to provide an overview of how enzyme detergents work and best practices for cleaning instruments to support infection prevention.
With the variety and diversity of chemical treatments available to healthcare facilities, it can be difficult to know which chemistry removes a particular type of organic soil from the surface of surgical instruments. In recent years, enzymatic detergents have emerged as an effective way to remove stubborn organic debris such as protein-based stains, blood, fibrin, mucus and triglyceride-based stains such as oils and fats.
Enzymes are a class of proteins that consist of a long chain of amino acids held together by peptide bonds. Enzymes are present in the formation and degradation of all biological substances where they act as biocatalysts that accelerate or initiate reactions without being consumed in the process.1 According to The Behavior of Proteins, “Enzymes are the most efficient catalysts known; they can increase a rate of reaction by a factor of 10-2 over uncatalyzed reactions. Nonenzymatic catalysts, in contrast, typically enhance the rate of reaction by factors of 10-2 to 10-4.“2
Enzymes are produced by fermentations from biological systems such as yeast, fungi and bacteria and are considered renewable, environmentally friendly components.3,4
Because of their ability to speed up reactions, enzymes are well suited for cleaning chemistries. In fact, they begin working on contact to digest biological soils. How enzymes work can be compared to a pair of scissors, “cutting off” soils piece by piece from the surface. All enzymes have active sites in their structure that interact with a substrate (e.g., food soils, biosoils such as blood, human oils, fats) causing a series of reactions to occur. The enzyme acts as a catalyst when the substrate is attached to the enzyme’s active site. Simply put, the enzyme breaks up the substrate (soil molecule). Once the transformation of the substrate is complete, the enzyme releases itself and is ready to begin the process again on another molecule.
Use of enzymes in consumer products started with the addition of dried pancreatic extracts to powdered laundry detergents in the early 20th century.5 After 1950, bacterial proteases became the enzymes of choice in household detergents because of their improved stability characteristics.6 This paved the way for broad acceptance of enzymes in consumer products.
Enzymes are now widely included in many household and commercial cleaning products and combined in multi-purpose formulations to work on a number of different types of soils. Detergents and cleaning solutions used for cleaning surgical instruments have developed similarly.
Enzymes are specific in terms of the type of soil they remove. There are four classes of enzymes commonly used in detergent formulations:
• Proteases break down and digest proteins, dissolving blood and body soils.7
• a-Amylases break down carbohydrates, starches and sugars. This is typically used in laundry to remove food soils.8
• Lipases break down fats and oils. This enzyme is especially useful in cleaning fatty soils associated with specific surgeries and patient populations.9
• Celluloses break down cellulose fibers. This enzyme is typically used in the textile industry for fabric treatments.10
Although new enzymatic detergent formulations are very effective, enzymes work best under certain environmental conditions such as specific temperature ranges, pH levels, and washer settings and in combination with other chemical ingredients.
Each type of enzyme has its own optimal temperature at which an enzyme’s catalytic activity is at its greatest. A wash temperature that is too high for a specific enzyme will denature it, thus disabling the enzyme’s normal activity. Enzymes used in automated washer cycles are often selected based on their stability at different temperature ranges. Enzymes are not denatured by lower temperatures, but their ability to react rapidly may be greatly reduced.10
Like most chemical reactions, the rate of an enzyme-catalyzed reaction increases as the temperature is raised. However, once the optimum temperature is reached, hotter temperatures will only decrease the effectiveness of the enzyme activity.
A new introduction to the instrument reprocessing market includes enzymatic detergent formulations that are engineered with two enzymes that work together as a system to be functional in both low and high wash temperatures.
The pH of the detergent formulation must also be carefully balanced with each enzyme ingredient; pH higher or lower than what is normal for a particular enzyme will denature it, thereby disabling the enzyme’s activity. Each type of enzyme has its own optimal pH at which an enzyme’s catalytic activity is at its greatest.11
In addition, water hardness can affect the enzyme activity. High levels of calcium and magnesium ions in water can elevate the pH, inhibiting enzyme activity. Detergent manufacturers may add sequestering agents, which bind these heavy metal ions, in the enzyme formula as an easy correction for this problem.
To ensure that enzymes are at their peak effectiveness, automated washer settings must also be taken into account. The detergent dosage, type of washing cycle, time of washing steps, and temperature should be calibrated to work with the type of enzyme detergents being used to achieve optimal efficiency. Detergent manufacturers must ensure that other ingredients such as surfactants, or anti-scaling agents are selected carefully so that they don’t interfere with enzyme active sites that are responsible for reacting with soils.12
The storage of enzymatic detergents is also an important consideration. High heat and high humidity will disable enzymes, degrading their cleaning ability.13 To solve this, enzymatic products should be stored at room temperature and low humidity conditions.
Finally, in order for an enzyme to perform at its full potential, the soiled surface must remain hydrated throughout the cleaning process. Pre-cleaners ensure that the soil on the surgical instrument remains hydrated in transit from the OR suite to the sterile processing department.
Today there are several types of enzymatic cleaners available in a variety of formulations, including liquids, concentrates, solids, and foam. In addition, there are aggressive, mild, and neutral formulations widely available to address the various types of soils found on surgical instruments. In general, the better performing products are those with relatively high and stable enzyme levels. Products containing high protease levels are particularly well suited for most surgical soils because the material associated with these soils are protein-based.
A current trend in the marketplace is the development of products that are easy to use and handle. Besides containing highly effective enzymes and agents to resist scaling and corrosion, solid detergents offer the additional benefit of greatly reduced product packaging and weight, which makes for easy transportation, storage and use.
When evaluating enzyme-based cleaners, it is important to consider the types of soils on which they will be used. Low- and high-temperature enzymatic formulation systems are a great option for effective cleaning performance because of their range. But ask your chemical provider how to improve the effectiveness and performance of enzymatic detergents, they will likely be able to recommend a formulation that suits your needs. Also, it is important to calibrate automated washers so the enzymes are most effective. Finally, it’s important to become familiar with the material safety data sheets (MSDS) for the products you use, read product labels and train staff on the proper product handling and storage.
Barbara Choczaj is a scientist, inventor and product formulator with Ecolab Healthcare. She holds a bachelor and master of science degree from the University of Adam Mickiewicz in Poznan, Poland. She can be reached at Barbara.firstname.lastname@example.org.
1-2. Campbell M. The Behavior of Proteins: Enzymes. Biochemistry, 5th Ed. Belmont, CA: Thomson-Brooks/Cole.:2006:131.
3. Bass JE. Development of New Proteases for Detergents. Enzymes in Detergency. New York, NY: Marcel Dekker Inc.:1997:33.
4. Bass JE. Manufacturing and Downstream Processing of Detergent Enzymes. Enzymes in Detergency. New York, NY: Marcel Dekker Inc.:1997; 251-256.
5-9. Bass JE. Enzymes: Their Applications and Biochemical Characterization. Enzymes in Detergency, New York, NY: Marcel Dekker Inc.,1994: 35-39; 300-302; 303-307.
10-11. Williams G. Enzymes. Advanced Biology for You, Cheltenham, UK: Nelson Thomes Ltd., 2003: pp63-80.
12-13. Bass JE. Enzymes: Their Applications and Biochemical Characterization. Enzymes in Detergency, New York, NY: Marcel Dekker Inc.,1994: 45-46, 239.