High-Level Disinfection and Sterilization

William A. Rutala

David J. Weber

Each year in the United States, there are ˜53 000 000 outpatient surgical procedures and 46 000 000 inpatient surgical procedures.¹ For example, there were over 6.9 million upper gastrointestinal (GI), 11.5 million lower GI, and 228 000 biliary endoscopies performed in 2009.² Each of these procedures involves contact by a medical device or surgical instrument with a patient’s sterile tissue, mucous membranes, or nonintact skin. A major risk in all such procedures is the introduction of pathogenic microbes, which can lead to infection. Failure to properly disinfect or sterilize equipment may lead to transmission via contaminated medical and surgical devices (eg, carbapenem-resistant Enterobacteriaceae [CRE]).³^,⁴

Multiple studies in many countries have documented lack of compliance with established guidelines for disinfection and sterilization.⁵ Failure to comply with evidence-based guidelines has led to numerous outbreaks and patient exposures.⁶ In fact, nearly all infections and patient exposures associated with reprocessing medical or surgical instruments involve high-level disinfection (HLD) of reusable semicritical items.⁶^,⁷^,⁸ Due to noncompliance with recommended reprocessing procedures, the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA) issued a health advisory alerting healthcare providers and facilities (including outpatient care facilities such as specialty clinics, ambulatory surgery centers) about the public health need to properly maintain, clean, disinfect, and sterilize reusable medical devices in September 2015.⁹ In this updated version of a previous chapter on this subject,¹⁰^,¹¹^,¹²^,¹³^,¹⁴ we will examine reprocessing of semicritical items (eg, endoscopes, endocavitary probes) and critical items (eg, surgical instruments).

RATIONAL APPROACH TO DISINFECTION AND STERILIZATION

About 50 years ago, Earle H. Spaulding¹⁵ devised a rational approach to disinfection and sterilization of patient-care items or equipment. This classification scheme is so clear and logical that it has been retained, refined, and successfully used by infection control professionals and others when planning methods for disinfection or sterilization.¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸^,¹⁹^,²⁰^,²¹ Spaulding believed that the nature of disinfection could be understood more readily if instruments and items for patient care were divided into three categories based on the degree of risk of infection involved in the use of the items. Although the scheme remains valid, there are some examples of disinfection studies with viruses, mycobacteria, protozoa, and prions as well as disinfectants that challenge the current definitions and expectations of high- and low-level disinfection.²² The three categories Spaulding described were critical, semicritical, and noncritical.

Critical Items

Critical items are so called because of the high risk of infection if such an item is contaminated with any microorganism, including bacterial spores. Thus, it is critical that objects that enter sterile tissue or the vascular system be sterile because any microbial contamination could result in disease transmission. This category includes surgical
instruments, cardiac and urinary catheters, implants, arthroscopes, laparoscopes, and ultrasound probes used in sterile body cavities. Most of the items in this category should be purchased as sterile or be sterilized by steam sterilization if possible. If heat sensitive, the object may be treated with ethylene oxide (ETO), hydrogen peroxide gas plasma, vaporized hydrogen peroxide vapor, or hydrogen peroxide vapor plus ozone or by liquid chemical sterilants if other methods are unsuitable. Tables 40-1, 40-2, 40-3 summarize sterilization processes and liquid chemical sterilants and the advantages and disadvantages of each. Sterilization technologies can be relied upon to produce sterility only if cleaning, to eliminate organic and inorganic material as well as microbial load, precedes treatment.²⁵^,²⁶^,²⁷^,²⁸^,²⁹^,³⁰ Other issues that sterile reprocessing and operating room professionals must deal with when reprocessing instruments include weight limits for instrument trays, wet packs, packaging, loaned instruments, cleaning monitoring, and water quality.²⁷^,³¹^,³²

TABLE 40-1 Methods for High-Level Disinfection and Sterilization of Medical and Surgical Instruments^a

*Process*	*Level of microbial inactivation*	*Method*	*Examples (with processing times)*	*Healthcare application (examples)*
Sterilization^b	Destroys all microorganisms, including bacterial spores	High temperature	Steam (˜40 min), dry heat (1-6 h depending on temperature)	Heat-tolerant critical (surgical instruments) and semicritical patient-care items
		Low temperature	Ethylene oxide gas (˜15 h), hydrogen peroxide gas plasma (28-38 min, NX), hydrogen peroxide and ozone (46-60 min, VP4), hydrogen peroxide vapor (28-55 min, V-Pro MAX)	Heat-sensitive critical and semicritical patient-care items
		Liquid immersion	Chemical sterilants^c: >2% glut (10 h at 20°C-25°C); 1.12% glut with 1.93% phenol (12 h at 25°C); 7.35% HP with 0.23% PA (3 h at 20°C); 7.5% HP (6 h at 20°C); 1.0% HP with 0.08% PA (8 h at 20°C); ˜0.2% PA (6 min at 46-55°C)	Heat-sensitive critical and semicritical patient-care items that can be immersed
High-level disinfection (HLD)	Destroys all microorganisms except some bacterial spores	Heat-automated	Pasteurization (65°C-77°C, 30 min)	Heat-sensitive semicritical items (eg, respiratory therapy equipment)
		Liquid immersion	Chemical Sterilants/HLDs^c: >2% glut (20-90 min at 20-25°C); 2.5% glut (5 min at 35°C); 0.55% OPA (12 min at 20°C); 1.12% glut with 1.93% phenol (20 min at 25°C); 7.35% HP with 0.23% PA (15 min at 20°C); 7.5% HP (30 min at 20°C); 1.0% HP with 0.08% PA (25 min at 20°C); 400-450 free chlorine (10 min at 30°C); 2.0% HP (8 min at 20°C); 3.4% glut with 20.1% isopropanol (5 min at 25°C)	Heat-sensitive semicritical items (eg, GI endoscopes, bronchoscopes, endocavitary probes)
glut, glutaraldehyde; HP, hydrogen peroxide; PA, peracetic acid; OPA, ortho-phthalaldehyde; ppm, parts per million; EPA, Environmental Protection Agency; FDA, Food and Drug Administration; GI, gastrointestinal.
^aModified from Rutala and Weber^{10,11,12,13,14} and Kohn.²³ ^bPrions (such as Creutzfeldt-Jakob disease) exhibit an unusual resistance to conventional chemical and physical decontamination methods and are not readily inactivated by conventional sterilization procedures. ^cConsult the FDA-cleared package insert for information about the cleared contact time and temperature, and see reference²⁴ for discussion why >2% glutaraldehyde products are used at a reduced exposure time (2% glutaraldehyde at 20 min, 20°C). Increasing the temperature using an automated endoscope reprocess (AER) will reduce the contact time (eg, OPA 12 min at 20°C but 5 min at 25°C in AER). Exposure temperatures for some high-level disinfectants above varies from 20°C to 25°C; check FDA-cleared temperature conditions.²⁴ Tubing must be completely filled for high-level disinfection and liquid chemical sterilization. Material compatibility should be investigated when appropriate (eg, HP and HP with PA may cause functional damage to endoscopes).

Semicritical Items

Semicritical items are those that come in contact with intact mucous membranes or nonintact skin. Respiratory therapy and anesthesia equipment, some endoscopes, laryngoscope blades and handles,¹¹^,³³ esophageal manometry probes, endocavitary probes, nasopharyngoscopes, prostate biopsy probes,³⁴ infrared coagulation (IRC) device,³⁵ anorectal manometry catheters, cystoscopes, ultrasound probes used on nonintact skin or mucous membranes (use probe cover when available), and diaphragm fitting rings are included in this category.¹¹^,¹² These medical devices should be free of all microorganisms, although small numbers

of bacterial spores may be present. Intact mucous membranes, such as those of the lungs or the GI tract, generally are resistant to infection by common bacterial spores but susceptible to other organisms such as bacteria, mycobacteria, and viruses. Semicritical items minimally require HLD using chemical disinfectants. Glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde (OPA), peracetic acid, hypochlorite (via superoxidized water) and peracetic acid with hydrogen peroxide are cleared by the FDA²⁴ and are dependable high-level disinfectants provided the factors influencing germicidal procedures are met (Tables 40-1 and 40-2). When a disinfectant is selected for use with certain patient-care items, the chemical compatibility after extended use with the items to be disinfected also must be considered.

TABLE 40-2 Summary of Advantages and Disadvantages of Chemical Agents Used as Chemical Sterilants or as High-Level Disinfectants (HLD)

*Sterilization method*	*Advantages*	*Disadvantages*
Peracetic acid/hydrogen peroxide	No activation required	Material compatibility concerns (lead, brass, copper, zinc) both cosmetic and functional Limited clinical experience Mucous membrane and respiratory health effects Potential for eye and skin damage
Glutaraldehyde	Numerous use studies published Relatively inexpensive Excellent material compatibility	Respiratory irritation from glutaraldehyde vapor Pungent and irritating odor Relatively slow mycobactericidal activity (unless other disinfectants added such as phenolic, alcohol) Coagulates blood and fixes tissue to surfaces Allergic contact dermatitis ACGIH recommends limiting employee exposure to ceiling concentration of 0.05 ppm
Hydrogen peroxide (standard)	No activation required May enhance removal of organic matter and organisms No disposal issues No odor or irritation issues Does not coagulate blood or fix tissues to surfaces Inactivates Cryptosporidium at 6%-7.5% Use studies published	Material compatibility concerns (brass, zinc, copper, and nickel/silver plating) both cosmetic and functional Serious eye damage with contact
Ortho-phthalaldehyde (OPA)	Fast acting high-level disinfectant No activation required Odor not significant Excellent materials compatibility claimed Does not coagulate blood or fix tissues to surfaces claimed Relatively rapid mycobactericidal activity	Stains protein gray (eg, skin, mucous membranes, clothing, and environmental surfaces) More expensive than glutaraldehyde Eye irritation with contact Slow sporicidal activity Anaphylactic reactions to OPA in bladder cancer patients with repeated exposure to OPA through cystoscopy
Peracetic acid	Standardized cycle (eg, Liquid Chemical Sterilant Processing System using Peracetic Acid, rinsed with extensively treated potable water) Low temperature (50°C-55°C) liquid immersion sterilization Environmental friendly by-products (acetic acid, O₂, H₂O) Fully automated Single-use system eliminates need for concentration testing May enhance removal of organic material and endotoxin No adverse health effects to operators under normal operating conditions Compatible with many materials and instruments Does not coagulate blood or fix tissues to surfaces Sterilant flows through scope facilitating salt, protein, and microbe removal Rapidly sporicidal Provides procedure standardization (constant dilution, perfusion of channel, temperatures, exposure)	Potential material incompatibility (eg, aluminum anodized coating becomes dull) Used for immersible instruments only Biological indicator may not be suitable for routine monitoring One scope or a small number of instruments can be processed in a cycle More expensive (endoscope repairs, operating costs, purchase costs) than high-level disinfection Serious eye and skin damage (concentrated solution) with contact Point-of-use system, no sterile storage An AER using 0.2% peracetic acid not FDA-cleared as sterilization process but HLD
Improved hydrogen peroxide (2.0%); high-level disinfectant	No activation required No odor Nonstaining No special venting requirements Manual or automated applications 12-month shelf life, 14-day reuse 8 min at 20°C high-level disinfectant claim	Material compatibility concerns due to limited clinical experience Organic material resistance concerns due to limited data
AER, automated endoscope reprocessor; FDA, Food and Drug Administration; ACGIH, American Conference of Governmental Industrial Hygienists. All products effective in presence of organic soil, relatively easy to use, and have a broad spectrum of antimicrobial activity (bacteria, fungi, viruses, bacterial spores, and mycobacteria). The above characteristics are documented in the literature; contact the manufacturer of the instrument and HLD/chemical sterilant for additional information. All products listed above are FDA-cleared as chemical sterilants except OPA and 2% accelerated hydrogen peroxide, which are FDA-cleared high-level disinfectant. Modified from Rutala and Weber.^{10,11,12,13,14}

TABLE 40-3 Summary of Advantages and Disadvantages of Commonly Used Sterilization Technologies

*Sterilization method*	*Advantages*	*Disadvantages*
Steam	Nontoxic to patient, staff, environment Cycle easy to control and monitor Rapidly microbicidal Least affected by organic/inorganic soils among sterilization processes listed Rapid cycle time Penetrates medical packing, device lumens	Deleterious for heat-sensitive instruments Microsurgical instruments damaged by repeated exposure May leave instruments wet, causing them to rust Potential for burns
Hydrogen peroxide gas plasma	Safe for the environment and healthcare personnel Leaves no toxic residuals Cycle time is 28-38 min and no aeration necessary Used for heat- and moisture-sensitive items since process temperature <50°C Simple to operate, install (208 V outlet), and monitor Compatible with most medical devices Only requires electrical outlet Microbicidal efficacy data	Cellulose (paper), linens and liquids cannot be processed Endoscope or medical device restrictions based on lumen internal diameter and length (see manufacturer’s recommendations) (eg, single and dual channel device with stainless steel lumen that is ≥1.0 mm internal diameter and ≤150 mm in length) Requires synthetic packaging (polypropylene wraps, polyolefin pouches) and special container tray Hydrogen peroxide may be toxic at levels >1 ppm TWA Organic matter reduces microbicidal activity
100% Ethylene oxide (ETO)	Penetrates packaging materials, device lumens Single-dose cartridge and negative-pressure chamber minimizes the potential for gas leak and ETO exposure Simple to operate and monitor Compatible with most medical materials	Requires aeration time to remove ETO residue ETO is toxic, a probable carcinogen, and flammable ETO emission regulated by states but catalytic cell removes 99.9% of ETO and converts it to CO₂ and H₂O ETO cartridges should be stored in flammable liquid storage cabinet Lengthy cycle/aeration time Organic matter reduces microbicidal activity
Vaporized hydrogen peroxide	Safe for the environment and healthcare personnel It leaves no toxic residue; no aeration necessary Cycle time, 28-55 min Used for heat and moisture sensitive items (metal and nonmetal devices)	Medical devices restrictions based on lumen internal diameter and length—see manufacturer’s recommendations (eg, single-channel device with stainless steel lumen that is ≥0.7 mm internal diameter and ≤500 mm in length) Not used for liquid, linens, powders, or any cellulose materials Requires synthetic packaging (polypropylene) Limited materials compatibility data Limited clinical use data Limited comparative microbicidal efficacy data Organic matter reduces microbicidal activity
Hydrogen peroxide and ozone	Safe for the environment and healthcare personnel Uses dual sterilants, hydrogen peroxide and ozone No aeration needed due to no toxic by-products Compatible with common medical devices Cycle time, 46-70 min FDA cleared for general instruments and multi-channel flexible endoscopes (see manufacturer’s instructions)	Endoscope or medical device restrictions based on lumen internal diameter and length (see manufacturer’s recommendations) (eg, single-and dual-channel device with stainless steel lumen that is ≥0.7 mm internal diameter and ≤500 mm in length) Limited clinical use data Limited materials compatibility data Limited microbicidal efficacy data Requires synthetic packaging (polypropylene wraps, polyolefin pouches) and special container tray Organic matter reduces microbicidal activity
ETO, ethylene oxide; FDA, Food and Drug Administration; TWA, time-weighted average. Modified from Rutala and Weber.^{10,11,12,13,14}

The complete elimination of all microorganisms in or on an instrument with the exception of small numbers of bacterial spores is the traditional definition of HLD. FDA’s definition of HLD is a sterilant used for a shorter contact time to achieve at least a 6-log₁₀ kill of an appropriate Mycobacterium species. Cleaning followed by HLD should eliminate all pathogens capable of causing infection.

Semicritical items should be rinsed with sterile water after HLD to prevent their contamination with organisms that may be present in tap water, such as nontuberculous mycobacteria (NTM), Legionella, or Gram-negative bacilli such as Pseudomonas.³⁶ In circumstances where rinsing with sterile water rinse is not feasible, a tap water or filtered water (0.2 µm filter) rinse should be followed by an alcohol rinse and forced-air drying.¹⁴^,³⁷^,³⁸ Forced-air drying markedly reduces bacterial contamination of stored endoscopes, most likely by removing the wet environment favorable for bacterial growth.³⁷ After rinsing, items should be dried and stored (eg, packaged or hung) in a manner that protects them from recontamination.

Some items that may come in contact with nonintact skin for a brief period (ie, hydrotherapy tanks, ultrasound probes on intact skin [includes central line puncture site]) are usually considered noncritical surfaces and are disinfected with low- or intermediate-level disinfectants.¹⁴^,³⁹ Since hydrotherapy tanks have been associated with spread of infection, some facilities have chosen to disinfect them with recommended levels of chlorine.¹⁴^,³⁹

Noncritical Items

Noncritical items are those that come in contact with intact skin but not mucous membranes. Intact skin acts as an effective barrier to most microorganisms; therefore, the sterility of items coming in contact with intact skin is “not critical.” Examples of noncritical items are bedpans, blood pressure cuffs, crutches, bed rails, bedside tables, patient furniture, toys,⁴⁰ portable equipment (eg, wheel chairs, infusion pumps, pulse oximeters, medication carts)⁴¹^,⁴² and floors.⁴³^,⁴⁴ In contrast to critical and some semicritical items, most noncritical reusable items may be decontaminated where they are used and do not need to be transported to a central processing area. There is virtually no documented risk of transmitting infectious agents to patients via noncritical items⁴⁵ when they are used as noncritical items and
do not contact nonintact skin and/or mucous membranes. However, these items (eg, bedside tables, bed rails) could potentially contribute to secondary transmission by contaminating hands or gloves of healthcare personnel (HCP) or by contact with medical equipment that will subsequently come in contact with patients.⁴⁶ Evidence-based practices for disinfection of noncritical environmental surfaces and equipment in healthcare facilities using a bundle approach are available.⁴⁷

HIGH-LEVEL DISINFECTION OF SEMICRITICAL ITEMS

Semicritical items are those that come in contact with mucous membranes or nonintact skin. Respiratory therapy and anesthesia equipment, GI endoscopes, bronchoscopes, laryngoscopes, transesophageal echocardiogram (TEE) probes, tonometers, endocavitary probes, transrectal ultrasound-guided (TRUS) prostate biopsy probes,³⁴ cystoscopes, hysteroscopes, IRC devices and diaphragm fitting rings are included in this category.¹² These medical devices should be free of all microorganisms (ie, mycobacteria, fungi, viruses, bacteria), although small numbers of bacterial spores may be present. Intact mucous membranes, such as those of the lungs or the GI tract, generally are resistant to infection by common bacterial spores but susceptible to other organisms such as bacteria, mycobacteria, and viruses. Semicritical items minimally require HLD using chemical disinfectants. Glutaraldehyde, hydrogen peroxide, OPA, peracetic acid, and peracetic acid with hydrogen peroxide, and a chlorine-based system are cleared by the FDA²⁴ and are dependable high-level disinfectants provided the factors influencing germicidal procedures are met. Table 40-2 lists the FDA-cleared high-level disinfectants and chemical sterilants with the advantages and disadvantages of each. The exposure time for most high-level disinfectants varies from 8 to 45 minutes at 20°C-25°C.²⁴ As with all medications and devices, users must be familiar with the manufacturer’s instructions for use (IFU). When a disinfectant is selected for use with certain patient-care items, the chemical compatibility after extended use with the items to be disinfected also must be considered. Disinfection strategies for some semicritical items (eg, applanation tonometers, rectal/vaginal probes) are highly variable.⁴⁸

Since semicritical equipment has been associated with reprocessing errors that result in patient lookback and patient notifications, it is essential that control measures be instituted to prevent patient exposures.⁶^,⁴⁹ Before new equipment (especially semicritical equipment as the margin of safety is less than that for sterilization)⁵⁰ is used for patient care on more than one patient, reprocessing procedures for that equipment should be developed. The FDA requests that the device manufacturer include at least one validated cleaning and disinfection/sterilization protocol in the labeling for their device. HCP should receive training on the safe use and reprocessing of the equipment and be competency tested. At the University of North Carolina (UNC) Hospitals, to ensure patient-safe instruments, all HCP that reprocess semicritical instruments (eg, instruments that contact a mucous membrane such as vaginal probes, endoscopes, prostate probes) are required to attend a 3-hour class on HLD of semicritical instruments initially and an 1-hour refresher class annually. The 3-hour class includes the rationale for and importance of HLD and discussion of high-level disinfectants and exposure times, reprocessing steps, monitoring minimum effective concentration, personal protective equipment, and the reprocessing environment (eg, establish “dirty-to-clean” flow). Infection prevention rounds or audits should be conducted at least annually in all clinical areas that reprocess critical and semicritical devices to ensure adherence to the reprocessing guidelines, manufacturers’ IFU and institutional policies. This includes reprocessing critical and semicritical medical and surgical instruments in outpatient care facilities as many patient exposures and infections have occurred in this setting.⁵¹ Results of infection prevention rounds should be provided to the unit managers, and deficiencies in reprocessing should be corrected and the corrective measures documented to infection prevention within 30 days. Patient safety issues such as the wrong contact time, temperature, or concentration of high-level disinfectant require immediate correction and follow-up.⁶^,⁴⁹

Semicritical items that will have contact with mucous membranes of the GI tract or upper respiratory tract should be rinsed with sterile water or filtered water or tap water followed by an alcohol rinse.¹⁴^,³⁸ An alcohol rinse and forcedair drying markedly reduces the likelihood of contamination of the instrument (eg, endoscope), most likely by removing the wet environment favorable for bacterial growth.³⁷ After rinsing, items should be dried and stored (eg, packaged or hung) in a manner that protects them from damage or contamination. Drying also retards biofilm formation.³⁰^,⁵² Using an automated drying and storage cabinet, a recent paper demonstrated that internal channels were dry at 1 hour and external surfaces at 3 hours. With the standard storage cabinet, there was residual internal fluid at 24 hours, whereas external surfaces were dry at 24 hours.⁵³ There is no recommendation to use sterile or filtered water rather than tap water for rinsing semicritical equipment that will have contact with the mucous membranes of the rectum (eg, rectal probes, anoscope) or vagina (eg, vaginal probes).¹⁴

Semicritical items represent the greatest risk of disease transmission as far more healthcare-associated infections have been caused by reusable semicritical items than critical or noncritical items.¹¹^,¹² There is virtually no documented risk of transmitting infectious agents to patients via noncritical items⁴⁵ when they are used as noncritical items and do not contact nonintact skin and/or mucous membranes. Similarly, critical items are rarely³⁰^,⁵⁴ associated with disease transmission. In contrast, semicritical items (eg, GI endoscopes) have been associated with more than 150 outbreaks (Table 40-4).

REPROCESSING SEMICRITICAL ITEMS

Reprocessing of GI Endoscopes and Bronchoscopes

More healthcare-associated infection outbreaks (>130 outbreaks) and patient exposures have been linked to contaminated GI endoscopes and bronchoscopes than to any other reusable medical device.⁷^,⁸ The reason for reprocessing failure will only be briefly discussed. There are at least two (and probably three) reasons for this reprocessing failure and why outbreaks continue to occur.⁵⁰ First, studies have shown that the internal channel of GI endoscopes, including duodenoscopes, may contain 10^7-10 (7-10-log₁₀) enteric microorganisms.⁶⁹^,⁷⁰ Investigations have demonstrated that
the cleaning step in endoscope reprocessing results in a 2-6-log₁₀ reduction of microbes and the HLD step results in another 4-6-log₁₀ reduction of mycobacteria for a total 6-12-log₁₀ reduction of microbes.⁶⁹^,⁷⁰^,⁷¹ Thus, the margin of safety associated with cleaning and HLD of GI endoscopes is minimal or nonexistent (level of contamination: 4-log₁₀ or 10 000 microbes [maximum contamination, minimal cleaning/HLD] to -5-log₁₀ [minimum contamination, maximum cleaning/HLD]). Therefore, any deviation from proper reprocessing (such as crevices that harbor microorganisms associated with the elevator channel or improper positioning of the elevator lever)⁷² could lead to failure to eliminate contamination with a possibility of subsequent patient-to-patient transmission. This low (or nonexistent) margin of safety associated with endoscope reprocessing compares to the 17-log₁₀ margin of safety associated with cleaning and sterilization of surgical instruments.⁵⁰ This is the reason that semicritical items represent the greatest risk of disease transmission via a reusable medical or surgical instrument and critical items are rarely⁵⁴ associated with infection.

TABLE 40-4 Infections/Outbreaks Associated With Semicritical Medical Devices^a

*Instruments*	*# Outbreaks/infections*	*# Outbreaks/infections with bloodborne pathogens*
Vaginal probes	0^b	0
Nasal endoscopes	0	0
Hysteroscopes	0	0
Laryngoscopes	2^55,56,57	0
Urologic instrumentation (eg, cystoscopes, ureteroscopes)	8^{46,47,48,49,50,51,52,53}	0
Transrectal-ultrasound guided prostate probes	1⁵⁸	0
Transesophageal echocardiogram (TEE)	5^{59,60,61,62,63}	0
Applanation tonometers	2^64,65
GI endoscopes/bronchoscopes	>130^7,8	3HBV⁶⁶; HCV^67,68
Modified from Rutala and Weber¹²; HBV, hepatitis B virus; HCV, hepatitis C virus.
^aThese infections/outbreaks were found in the peer-review literature through PubMed and Google. ^bDoes not include outbreaks associated with contaminated ultrasound gel used with vaginal probes or transmission via healthcare personnel.

Second, the complexity of the endoscope and endoscope reprocessing is a reason for reprocessing failure. GI endoscopes not only have heavy microbial contamination (10⁷-10¹⁰ bacteria) but are complex with long, narrow channels; right-angle turns; and difficult to clean and disinfect components (eg, elevator region). Additionally, while evidence-based endoscope-reprocessing guidelines have been prepared by professional organizations (eg, Society of Gastroenterology Nurses, American Society of Gastrointestinal Endoscopists)³⁸^,⁷³^,⁷⁴ and the CDC¹⁴; unfortunately, there are also data that demonstrate that all of the steps associated with manual endoscope reprocessing are rarely performed (compliance of 1.4%), and some essential steps (eg, brushing all endoscope channels and components) are commonly not performed. Endoscope reprocessing was improved with the use of automated endoscope reprocessors (AERs) because most steps were automated and standardized.⁵

Third, biofilms could impact endoscope-reprocessing failure and continued endoscope-related outbreaks.⁷⁵ Alfa discussed the differences between a traditional biofilm that forms under continuously hydrated conditions (eg, water pipes) and a buildup biofilm that forms as an accumulation of material formed by repeated rounds of patient exposure, cleaning and disinfection, or sterilization and dry storage.³⁰ The buildup biofilm cycle involves repeated rounds of hydration and dry conditions that form a dried organic matrix with embedded organisms. It is unclear, but possible, that buildup biofilms contribute to failure of endoscope reprocessing.

Infection preventionists should ensure that institutional policies are consistent with national guidelines¹⁴^,³⁸ and manufacturers’ IFU and conduct infection prevention rounds periodically (eg, at least annually) in areas where endoscopes and other semicritical items are reprocessed to make certain there is compliance with policy. Based on the infection data and risks, the transition to sterilization of duodenoscopes was recommended by an FDA Panel in May 2015. Technologies to allow this change to occur are being developed⁷⁶ and FDA cleared and should be used when acceptable in terms of sterilization performance, scope performance (for disposable scopes), cost, throughput and compatibility of materials (eg, adhesives) to sterilization technology. Device and sterilization manufacturers, regulatory agencies, GI physicians, inpatient and outpatient endoscope reprocessing centers as well as professional organizations must reach a general agreement regarding the need for sterilization and the willingness to replace existing disinfection technologies. This transition will occur when we put “the needs of the patient first” and offer every patient an endoscope that is sterile and thus, devoid of potential pathogens.⁷⁶

Nasal Endoscopy

There are several types of scopes that are used to examine the nose and throat (eg, nasopharyngoscope, rhinolaryngoscopes).¹² Since they become contaminated during use, there is a risk of transmission of infection between patients. Flexible nasopharyngoscopy is a valuable tool enabling easy visualization of the upper aerodigestive tract. In the United States, three techniques are available to reprocess nasopharyngoscopes: manual HLD, use of an AER, and use of a disposable sheath with low-level disinfection.¹⁴^,⁷⁷^,⁷⁸^,⁷⁹ However, since sheaths/condoms/covers may have tears or breaks that compromise their integrity, there was hesitation to allow the use of a sheath to alter the recommendation of HLD. There are now two peer-reviewed publications
that validate the integrity of the sheath with nasopharyngoscopes along with low-level disinfection.⁸⁰^,⁸¹

Applanation Tonometers

Applanation tonometers are a possible vector for the transmission of infectious disease and outbreaks of epidemic keratoconjunctivitis (caused by adenovirus)⁴¹^,⁴² have been related to incompletely disinfected tonometers.⁴⁸^,⁶⁴^,⁶⁵ In view of the potential for transmission of viruses (eg, herpes simplex virus, adenovirus type 8, or human immunodeficiency virus [HIV])⁸² by tonometer tips, the CDC recommended⁸³ that the tonometer tips be wiped clean and disinfected for 5-10 minutes with 3% hydrogen peroxide, 5000 ppm chlorine, 70% ethyl alcohol, or 70% isopropyl alcohol. However, data suggest that 3% hydrogen peroxide and 70% isopropyl alcohol are not effective against adenovirus capable of causing epidemic keratoconjunctivitis and similar viruses and should not be used for disinfecting applanation tonometers.⁸⁴^,⁸⁵^,⁸⁶ For this reason the CDC guideline now recommends to wipe clean tonometer tips and then disinfect them by immersing for 5-10 minutes in either 5000 ppm chlorine or 70% ethyl alcohol.¹⁴^,⁸³^,⁸⁴^,⁸⁵^,⁸⁶ Structural damage to Schiotz tonometers has been observed with a 1:10 sodium hypochlorite (5000 ppm chlorine) and 3% hydrogen peroxide.⁸⁷ After disinfection, the tonometer should be thoroughly rinsed in tap water and air-dried before use. We believe that wiping the tonometer tips with a 70% isopropyl alcohol wipe is insufficient to prevent patient-to-patient transmission since two reports have found that disinfection of pneumotonometer tips between uses with a 70% isopropyl alcohol wipe contributed to outbreaks of epidemic keratoconjunctivitis caused by adenovirus type 8.⁸⁸^,⁸⁹

Of course, intraocular instruments must be cleaned and sterilized between patients. Eye instruments are very delicate and require special handling to prevent damage. Recommended practices are derived from evidence-based recommendations for cleaning and sterilizing all surgical instruments in general, from outbreaks of toxic anterior segment syndrome (TASS), and from manufacturers’ IFU.⁹⁰ TASS is an acute severe inflammatory reaction of the anterior chamber of the eye to a toxic contaminant (eg, detergent residues) introduced into the anterior chamber during intraocular surgery.⁹⁰

Endocavitary Probes (eg, Vaginal Probes)

Vaginal probes are used in sonographic scanning. A vaginal probe and all endocavitary probes without a probe cover are semicritical devices as they have direct contact with mucous membranes (eg, vagina, rectum, and pharynx). While one could argue that the use of the probe cover changes the category, the CDC guideline for disinfection and sterilization¹⁴ proposes that a new condom/probe cover should be used to cover the probe for each patient and since condoms/probe covers may fail,⁹¹^,⁹²^,⁹³^,⁹⁴^,⁹⁵ HLD of the probe also should be performed.¹⁴^,⁹⁶ The relevance of this recommendation is reinforced with the findings that sterile transvaginal ultrasound probe covers have a very high rate of perforations even before use (0%, 25%, and 65% perforations from three suppliers).⁹⁴ After oocyte retrieval use, Hignett and Claman found a very high rate of perforations in used endovaginal probe covers from two suppliers (75% and 81%),⁹⁴ while Amis and co-workers⁹⁷ and Milki and Fisch⁹¹ demonstrated a lower rate of perforations after use of condoms (0.9% and 2.0%, respectively). Rooks and coworkers found that condoms were superior to commercially available probe covers for covering the ultrasound probe (1.7% for condoms vs 8.3% leakage for probe covers).⁹⁸ These studies underscore the need for HLD of endocavitary probes between examinations. Although most ultrasound manufacturers have recommend the use of 2% glutaraldehyde for HLD of contaminated transvaginal transducers, the use of this agent has been questioned⁹⁹ because it may shorten the life of the transducer and may have toxic effects on the gametes and embryos.¹⁰⁰ An alternative procedure for disinfecting the endocavitary and surface probes is a hydrogen peroxide mist system, which uses 35% hydrogen peroxide at 56°C with the probe reaching no more than 40°C (ie, Trophon).¹² Another probe disinfection method that uses a UV-C chamber has been evaluated and is used in Europe and Canada but is not yet FDA cleared for use in the United States.⁹⁵^,¹⁰¹

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