March 11, 2013 — A nurse practitioner’s question: “I am wondering if there has been independent testing of enzymatic solutions? If a solution contains 10 percent alcohol and a perfume. Would an enzyme survive the alcohol content? It might be interesting to test different market solutions.”
Answer and Background
As you may remember from chemistry class, first, peptides linked together (via peptide bonds) form chains, or strings, of amino acids, which themselves, when linked together, form larger molecules called proteins.
Second, all enzymes are proteins, but not all proteins are enzymes. Third, in general, enzymes catalyze (that is, they facilitate, promote, initiate and/or control the rate of) certain chemical reactions (that otherwise, without their “assistance,” might not have been possible).
And, fourth, enzymes are specific in the type of molecules they break down, or “digest.”
These four properties, among others, cause enzymes not surprisingly to be an ideal tool for the cleaning industry and for reprocessing soiled surgical instruments and flexible endoscopes.
Types of enzymes
One type of enzyme, known as a “protease,” hydrolyzes these peptide bonds, causing larger (water-insoluble) protein molecules (dissolving blood is an example) to be broken down (e.g., digested) into smaller, more water-soluble amino acids.
In theory, patient debris containing proteins might be more easily removed from a soiled surgical instrument’s surfaces if they were cleaned using a detergent that contained protease.
[In the market to buy an enzymatic detergent to clean surgical instruments? Click the link.]
Another type of enzyme, known as a “lipase,” similarly digests, or breaks down, the chemical bonds holding fats and oils together, causing these substances to become smaller and more soluble in water.
Like with proteins, a soiled instrument’s surfaces that are contaminated with fats and oils may be more easily cleaned using a detergent that contains a lipase.
Alcohols may be added to a detergent to facilitate their cleaning of soiled surfaces, because, whereas fats and oils are insoluble in water, both are miscible in (and therefore more easily cleaned and rinsed away using an) alcohol.
Validation testing
It would be interesting and quite valuable to test (using a validated protocol) different types of detergents, to collect data and to assess whether one might clean (assessed by measuring the extent to which a marker was reduced after, compared to before, cleaning) the internal lumens of soiled reusable medical equipment better or more effectively than another.
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Indeed, validation testing could support the conclusion that enzymatic detergents intended to clean soiled, contaminated reusable surgical instruments (likely at the respective detergent label’s more concentrated formulation) may be more effective than detergents that do not contain enzymes.
The marketplace’s perception that enzymatic detergents are superior (to non-enzymatic detergents) may be as much a driving force behind their popularity as some data demonstrating their effectiveness for cleaning soiled surgical instruments and flexible endoscopes including gastrointestinal (GI) endoscopes. — Lawrence F Muscarella PhD
For a number of reasons, including debate about the testing protocol’s validity and applicability, there are limited data demonstrating an enzymatic detergent’s superiority for cleaning the internal lumens of complex surgical instruments, including gastrointestinal (GI) endoscopes.
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Therefore, the status quo of a practitioner’s personal experience and preferences (and cost), sometimes more so than the product’s demonstrated cleaning performance, remains an important driving force behind the selection of one type of detergent over another.
Nevertheless, validation testing could (but would not necessarily) confirm that enzymatic detergents may more effectively clean soiled instrument surfaces than detergents that do not contain enzymes. — Lawrence F Muscarella PhD
Perception is reality
Indeed, not to be overlooked, an important component of detergents (as much as their performance) is the perception in the marketplace of their superior cleaning effectiveness without necessarily any simulated in-use validation testing having been independently performed to confirm the detergent’s performance.
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Because the types of patient soils and bioburden encountered during GI endoscopy often contain proteins (e.g., blood, bodily fluids, mucous), the marketplace has generally concluded (correctly or not) that enzymatic detergents containing proteases would be expected to be more effective at cleaning the surfaces of a contaminated GI endoscope than those detergents not containing an enzyme.
Click here to read Dr. Muscarella’s related blog entitled “Protocol for ‘Prepping’ a GI Endoscope Prior to its Delayed Reprocessing.“
FDA regulation
Most detergents used in the fields of infection control and instrument reprocessing are class 1 devices subject to limited regulatory control by the FDA.
More specifically, detergents used to clean soiled instruments (unless associated with a specific claim or an automated process) are generally exempt from the regulatory requirements both of the design controls specified in the FDA’s Quality System Regulation (QSR) and of the 510(k)-clearance process.
Click here to read Dr. Muscarella’s related article entitled “The FDA’s Quality System Regulation.“
Whether this may change in time and detergents, like many different types of reusable devices including GI endoscopes, may become class 2 devices requiring a 510(k) clearance (for completeness, class 3 devices generally require a pre-market approval, or PMA) prior to being marketed in the U.S. is a subject of interest, speculation and debate, although it is likely if the detergent is associated with a specific performance claim, such as that it “reduces the amount of bioburden on a soiled instrument by 99.9%.”
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A review
Supporting this conclusion, Dr. Muscarella reviewed the labels of several enzymatic detergents and (with one exception) did not identify an enzymatic detergent labeled with the specific claim (or, indication for use) “to clean” soiled surgical or medical instruments, or, for example, to remove bioburden from their surfaces by a specific amount (e.g., “99.9%”).
Instead, the labels Dr. Muscarella reviewed generally state less specifically that the enzymatic detergent (either by way of a formal or informal “indications for use” statement):
- “enhances” the cleaning of soiled surgical instruments;
- is specially formulated “for cleaning,” or as a “cleaner” of, hard-to-remove patient bioburden inside GI endoscopes;
- “breaks down” patient debris;
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- “aids in the removal of bioburden and biofilms from soiled instrument’s surfaces;
- “reduces the level of bioburden” on a soiled instrument’s surfaces before sterilization; or
- “removes” blood, tissue, protein, vomit, mucous, fecal matter, or another body fluid from the surfaces of surgical instruments.
Not labeling an enzymatic detergent with the specific claim “to clean” soiled surgical or medical instruments is understandable.
Indeed, for the detergent’s manufacturer, making such a claim could:
- have significant regulatory implications for, and financial impact on, the detergent company;
- require more oversight by the FDA of the detergent company’s manufacturing operations; and
- require that the detergent first receive a 510(k) clearance before being marketed and sold in the U.S.
Suggesting the regulation of detergents could be as much about semantics and a manufacturer’s insightful selection of certain words to describe the detergent’s effectiveness as about performance and safety, the apparent omission from an enzymatic detergent’s labeling of the claim that the product “cleans” reusable medical instruments and GI endoscopes is not likely coincidental.
Click here to read Dr. Muscarella’s related blog entitled “Pre-Cleaning Gastrointestinal Endoscopes at Bedside.“
More so than the addition of a perfume or of alcohol (unless either is known to specifically denature the enzyme, hindering or preventing the detergent’s effectiveness), factors that affect a detergent’s cleaning performance include: (i) water quality (i.e., the quality of the water with which the detergent is mixed); (ii) water temperature; (iii) the detergent’s pH; (iv) the detergent’s concentration; (v) the time the soiled instrument is immersed in and exposed to the detergent; and (vi) the amount of soil on the contaminated instrument.
In response to the nurse practitioner’s originally posed question (see top of article), enzymes are inanimate catalysts, not bacteria that would be killed by exposure to alcohol or another type of disinfectant. But, that said, depending on its concentration, it would seem possible that an alcohol, such as iso-propyl alcohol, could partially or completely denature the protease in the enzymatic detergent, hindering its cleaning ability.
An enzymatic detergent’s effectiveness depends on several factors, including the temperature of the water into which it is mixed, the detergent’s concentration, the amount of time the detergent remains in contact with the surgical instrument’s (or GI endoscope’s) soiled surfaces, and the amount of soil on the contaminated instrument.—Lawrence F Muscarella, PhD
Closing remarks
Published data showing one type of detergent is superior to another, whether or not the detergent contains one or more enzymes to “enhance” its cleaning, are limited and not necessarily independent or reliable.
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Although it could, the addition of (isopropyl or ethyl) alcohol to a detergent, with or without the addition, too, of a perfume, would not necessarily render the detergent ineffective, because the detergent’s reduction of water’s surface tension may prove to overcome any adverse effect that the alcohol might have on the enzymatic detergent’s effectiveness.
Article by: Lawrence F Muscarella, PhD, President, LFM Healthcare Solutions, LLC, a quality improvement company. Posted on 3-11-2013; updated 10-3-2014, Rev A.