Disinfection or Sterilization of a Contaminated Reusable Instrument?

Selection of the “right” sterilization or disinfection process, or technology, for reprocessing a specific type of reusable instrument may not always be straightforward. This is often because the instrument is damaged by heat and, therefore, cannot be easily and cost-effectively sterilized using pressurized steam.

For many types of reusable heat-sensitive instruments capable of transmitting diseases during a medical procedure, low-temperature sterilization technologies and robust disinfection processes were developed. To be sure, selection of the appropriate reprocessing technology is crucial to quality, safety and the prevention of healthcare-associated infections (HAIs).

In general, the documented risk of infection associated with the reuse of a instrument (i.e., low, moderate, high), contaminated with potentially pathogenic microorganisms, dictates whether its disinfection or sterilization is required to prevent disease transmission.

The following strategy explains how to select an appropriate reprocessing procedure for a specific type of reusable medical instrument.

Step 1.  Determine the reusable device’s “classification.”

The first step in this process is to determine whether the instrument is classified as “critical,” “semi-critical,” or “non-critical.”  Table 1, below, may be used to simplify this determination.

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Table 1: A widely accepted classification scheme for medical instruments.

A. Critical instruments penetrate sterile tissue, enter the vasculature, or contact the patient’s blood.

• Examples include cardiac catheters, biopsy forceps, and implants.

B. Semi-critical instruments, in contrast, are limited to contacting mucous membranes (e.g., those of the gastrointestinal [GI] tract, the pulmonary tract, or the oral cavity) or non-intact skin.

• Examples include GI endoscopes, “ENT” (ear-nose-throat) endoscopes, cystoscopes, and the blades and handles of rigid laryngoscopes.(1-4)

• The risk of infection associated with instruments in this category, while still potentially significant, is less than that of critical instruments.

Click here to read Dr. Muscarella’s related blog “The Reprocessing of Sheathed “ENT’ Endoscopes and Cystoscopes.”

Click here to read Dr. Muscarella’s related blog “On Reprocessing Skin Electrodes.”

C. Noncritical instruments, on the other hand, do not directly contact the patient, or only contact the patient’s intact skin.

• Examples include blood pressure cuffs, stethoscopes, and bedpans. Other examples of non-critical devices include environmental surfaces, such as walls, floors, and sink tops.

• Non-critical instruments pose the least, and a low, risk of infection if contaminated at the time of their use and contact with patients.

Click here to read Dr. Muscarella’s related blog “Decontamination of CPR Manikins.”

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Step 2. Understanding the differences between sterilization and the three levels of disinfection.

The next step in this process is to understand the differences between disinfection and sterilization.

Whereas sterilization is an absolute term that may be used to refer to processes that destroy all types of infectious agents, disinfection is a relative term, and processes that achieve it are classified into one of “three levels,” depending on their relative effectiveness. The higher the level of disinfection, the more effective the process.

Click here to read about a auditing program developed by Dr. Muscarella specifically designed to prevent infection-control breaches and associated infections (HAIs).

Presented another way, the more resistant the microorganism, the higher the level of disinfection (or sterilization) required to destroy it.  Table 2, below, explains the differences between the three levels of disinfection and sterilization.

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Table 2. The definitions, characteristics, and relative effectiveness of sterilization and disinfection’s three levels.

A.  Processes that achieves sterilization:

• are absolute, meaning they destroy all microorganisms, including bacterial endospores;
• are sporicidal, tuberculocidal, virucidal, fungicidal, and bactericidal;
• use bacterial endospores as biological indicators; and
• are regulated by the Food and Drug Administration (FDA).

Agents that achieve sterilization include pressurized steam, ethylene oxide gas, hydrogen peroxide plasma. Sterilization is used primarily to prevent reusable critical instruments from transmitting disease during their reuse.

B. Processes that achieve high-level disinfection (or, “HLD”):

•  destroy all pathogenic microorganisms, including some types of (but not all) bacterial endospores during relatively short exposure times;
• typically destroy high numbers of bacterial endospores during long exposures times;
• are sporicidal (limited), tuberculocidal, virucidal, fungicidal, and bactericidal;
• use mycobacteria as indicators of effectiveness; and
• are regulated by the FDA.

Agents that achieve HLD include 2% glutaraldehyde, 7.5% hydrogen peroxide, and 0.2% peracetic acid. HLD is used primarily to prevent reusable semi-critical instruments from transmitting disease during their reuse.

C. Processes that achieve intermediate-level disinfection (or, “ILD”):

• destroy many types of microorganisms including mycobacteria;
• are not sporicidal (note: in general, processes that achieve high-level disinfection are ordinarily sporicidal, like sterilization, but, unlike sterilization, may require extended exposure times (e.g., 32 hours) to destroy bacterial endospores);
• are tuberculocidal, virucidal, fungicidal, and bactericidal;
• may use mycobacteria and/or viruses as indicators of effectiveness; and
• are regulated by the Environmental Protection Agency (EPA).

Agents that achieve ILD include 70% isopropyl alcohol, iodophor and phenolic
compounds, and concentrated quaternary ammonium compounds (e.g., hospital cleaner/disinfectants with a tuberculocidal claim). ILD is used primarily to prevent reusable non-critical instruments from transmitting disease during their reuse.

D. Processes that achieve low-level disinfection (or, “LLD”):

• destroy some types of microorganisms;
• are neither sporicidal nor tuberculocidal;
• are virucidal (limited), fungicidal, and bactericidal;
• may use the hepatitis B virus and/or HIV as an indicator of effectiveness; and
• are regulated by the EPA.

Agents that achieve LLD include diluted quaternary ammonium compounds (e.g., hospital cleaner/disinfectants without a tuberculocidal claim). Like ILD, LLD is used primarily to prevent reusable non-critical instruments from transmitting disease during their reuse.

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Table 1 and Table 2, above, provide necessary information to determine whether disinfection or sterilization is required to prevent a specific reusable instrument from transmitting disease. This discussion is complemented by Table 3, which lists the relative resistance of potentially pathogenic microorganisms to disinfection and sterilization.

Step 3. Understanding the relative resistance of different types of microorganisms to sterilization and disinfection.

Dovetailing Table 1 and Table 2 with Table 3 simplifies selection of the appropriate reprocessing technology or method – namely, sterilization or one of the three levels of disinfection — to prevent a specific reusable instrument from transmitting disease.

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Table 3: The relative resistance of different types of microorganisms to sterilization, disinfection, in their decreasing resistance to disinfection and sterilization. (In general, bacterial endospores (and prions) are the hardest to destroy and lipid (or medium-sized) viruses the easiest to destroy.)

Prions:

• may require extended, multiple sterilization cycles; and
• may be responsible for transmissible spongiform encephalopathies.

[Want to read a book about Creutzfeldt Jakob disease, the history of transmissible subacute spongiform encephalopathies, or the scourge of prions? Click the link.]

Bacterial endospores:

• are destroyed by sterilization (although some bacterial endospores can also be destroyed by high-level disinfection).
• Examples include Geobacillus sterathermophilus and Bacillus subtilis.

Mycobacteria:

• are destroyed by sterilization, high-level disinfection and intermediate-level disinfection.
• Examples include Mycobacterium tuberculosis and Mycobacterium gordonae.

Non-lipid or small viruses:

• are destroyed by sterilization, high-level disinfection and intermediate-level disinfection.
• The polio virus is an example.

Fungi (molds and yeasts):

• are destroyed by sterilization, high-level disinfection and intermediate-level disinfection.
• Some fungi are also destroyed by low-level disinfection.
• Examples include Candida albicans and Aspergillus niger.

Vegetative bacteria:

• are destroyed by sterilization, high-level disinfection, intermediate-level disinfection, and low-level disinfection.
• Examples include Pseudomonas aeruginosa and Serratia marcescens.

Lipid or medium-sized viruses:

• are destroyed by sterilization, high-level disinfection, intermediate-level disinfection, and low-level disinfection.
• Examples include the hepatitis B virus and HIV.

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Step 4. Selection of the right reprocessing process for a specific reusable instrument.

Based on the aforementioned discussion (see: Tables 1-3), the appropriate reprocessing method for virtually any type of reusable instrument can be readily determined.

Click here to read Dr. Muscarella’s related blog “Recommendations to Prevent Infections Associated with Improperly Reprocessed Reusable Medical Equipment.”

For example, because they are classified as critical instruments, reusable biopsy forceps require sterilization (e.g., a steam autoclave) to prevent disease transmission. Heat-sensitive critical instruments, such as arthroscopes and laparoscopes, however, may be processed using a low-temperature sterilization technology.

Click here to read Dr. Muscarella’s related blog about a clinic’s improper disinfection of reusable biopsy forceps — which, as Table 1 displays, are critical instruments that, as discussed in Table 2, require sterilization — over a period of 14 years.

High-level disinfection using, for example, ortho-phthalaldehyde or glutaraldehyde, is recommended to prevent semi-critical instruments (damaged by steam sterilization), such as GI endoscopes, bromhcosocpes, and “ENT” endoscopes, from transmitting disease during their reuse. These types of reusable instruments contact mucous membranes — they do not ordinarily enter sterile tissue during routine use — and therefore sterilization, while ideal, is not required.

Click here to read Dr. Muscarella’s related blog about the safe use of the high-level disinfectant Cidex OPA, whose active ingredient is ortho-phthalaldehyde.

Low-level disinfection is generally recommended for the disinfection of non-critical devices and environmental surfaces. If, however, these devices or surfaces are visibly soiled with blood or other potentially infectious materials or fluids, then intermediate-level disinfection, which (unlike low-level disinfection) is tuberculocidal, is indicated. (Remember that cleaning of the instrument or environmental surface is always necessary before employing sterilization or disinfection.)

Once the differences between sterilization and disinfection are understood, along with how medical devices are classified, then whether sterilization or one of the three levels of disinfection is appropriate for a specific reusable instrument can be readily determined.— Lawrence F Muscarella, PhD

In closing, a more complete discussion of this topic is available in Dr. Muscarella’s peer-reviewed article “Prevention of disease transmission during flexible laryngoscopy,” which can be downloaded by clicking here.

Article by: Lawrence F Muscarella PhD; posted 9-3-2013.

See the next page for this blog’s references.

References

1. Rutala WA. APIC guideline for selection and use of disinfectants. Am J Infect Control 1996 Aug;24(4):313-42. Review.
2. American Society of Anesthesiologists. Recommendation for infection control for the practice of anesthesiology. (Second edition.), 1999.
3. Association of periOperative Registered Nurses.  Clinical issues. AORN J January 2000.
4. Asmerican Association of Nurse Anesthetists. Part III: Infection Control Procedures for Anesthesia Equipment. Revised, 1997.
5. Muscarella LF. High-level disinfection or “sterilization” of endoscopes? Infect Control Hosp Epidemiol 1996 Mar;17(3):183-7. Review.
6. Muscarella LF.  Are all sterilization processes alike? AORN J 1998 May;67(5):966-70, 973-6.
7. Alvarado CJ, Reichelderfer M. APIC guideline for infection prevention and control in flexible endoscopy. Association for Professionals in Infection Control. Am J Infect Control. 2000 Apr;28(2):138-55.
8. Garner JS, Favero MS. CDC guidelines for the prevention and control of nosocomial infections. Guideline for handwashing and hospital environmental control, 1985. Supersedes guideline for hospital environmental control published in 1981. Am J Infect Control 1986 Jun;14(3):110-29.
9. Centers for Disease Control and Prevention. Rapidly growing mycobacterial infection following liposuction and liposculpture–Caracas, Venezuela, 1996-1998. MMWR Morb Mortal Wkly Rep 1998 Dec 18;47(49):1065-7.
10. Simmons SA.  Laryngoscope handles:  A potential for infection AANA J 2000 Jun;68(3):233-6.
11. Welch-Allyn.  Operating instructions for the RL-150 Rhinolaryngoscope.
12. Rusch. Care and maintenance instructions for Rusch laryngoscope handles and blades.