Section II The Patient and Endoscopy

10.1055/b-0038-149307

6 Cleaning and Disinfection in Endoscopy

Bret T. Petersen

6.1 Introduction

Cleaning and disinfection of endoscopes are critical safety and quality tasks that all gastrointestinal endoscopy departments must be attentive to. The soiled environment in which endoscopes are used yields a significant bioburden for cleaning and eradication before their reuse in subsequent patients. The complexity of endoscope design further challenges the task of producing a microbe-free instrument. Our recognition of reprocessing requirements and adoption of standardized approaches to reprocessing developed slowly over several decades. ¹ The Spaulding criteria for critical instruments, which are those that contact intact but contaminated mucosal membranes, stipulate that reprocessing should achieve, at a minimum, high-level disinfection (HLD). This level of reprocessing eradicates all living bacteria, viruses, and most spores, unless present in high numbers. Current international guidelines for HLD all espouse stepwise processes, which include precleaning at the bedside, thorough submersion and manual cleaning, standardized disinfection by exposure to approved liquid chemical germicides (LCGs) at specific parameters, and followed by rinsing, drying, and appropriate storage. Recent outbreaks of infections subsequent to endoscopic retrograde cholangiopancreatography (ERCP) have been attributed to persistent contamination at the elevator mechanisms, despite appropriate reprocessing. This has prompted interim advice to ensure optimal training and oversight of cleaning staff while intensifying attention to all standard steps of HLD, plus consideration of local benefit of use of double reprocessing cycles, ethylene oxide sterilization after each procedure, adenosine triphosphate (ATP) testing to assay the adequacy of the cleaning phase of reprocessing, and intermittent or per procedure endoscope cultures after full HLD.

Recurring clusters of infections, primarily related to lapses in standard reprocessing steps, have repeatedly focused the attention of the medical community and the broader regulatory and patient communities on the issue of reprocessing. This has culminated in the development of multiple national and international standards and guidelines for reprocessing, from many affiliated medical and technical specialty groups. Despite differences in detail and specificity, most existing guidelines are highly uniform in their requirements. ² , ³ , ⁴ , ⁵ , ⁶ , ⁷

6.2 Principles of Disinfection

6.2.1 Definitions

The language of reprocessing employs numerous terms with varied derivations from both regulatory and scientific origins. Reprocessing refers to a validated process that is used to render a used or soiled medical device fit for a subsequent single use. ⁸ It typically includes steps to remove gross soil by cleaning (or washing), and disinfection or sterilization to inactivate microorganisms. Cleaning is the physical removal of soil and contaminants to minimize transfer from one patient to another or between uses in a single patient. It should enable successful subsequent disinfection or sterilization and prevent accumulation of residual soil throughout the useful life of the product. ⁹ Disinfection is the process that employs physical or chemical means to destroy pathogenic and nonpathogenic microorganisms present on inanimate objects, such as medical devices. Hence, disinfectants are the agents used to destroy the microorganisms. Individual agents are sometimes referred to as germicides, fungicides, sporicides, etc., based on the microorganisms they are designed to inactivate. In contrast, antiseptics are agents that reduce or eliminate microorganisms on skin or in living tissues.

Disinfection is commonly categorized by the degree of clearance of microorganisms: HLD eradicates all bacteria, viruses, and most but not all spores when present in high numbers; intermediate-level disinfection inactivates all bacteria, mycobacteria, and most viruses but not bacterial spores; low-level disinfection destroys most bacteria, viruses, and fungal spores, but some mycobacteria, nonlipid viruses, and bacterial spores remain viable.

Sterilization achieves 100% eradication of all forms of life or infectious agents. This degree of certainty cannot be measured or accurately achieved; hence, sterility is often equated to a very low probability of less than 10^–6 (< 1/10 ⁶ = less than one in a million) of a nonsterile unit following sterilization. This “sterility assurance level” (SAL) is required for injectable medications and medical devices by the Food and Drug Administration (FDA) in the United States. ¹⁰ HLD is also intended to reduce microbial load to a SAL of 10^–6, with the exception that some resistant spore forms are not eradicated.

The intensity of reprocessing for all medical devices is based on the Spaulding classification, which stipulates that the degree of disinfection or sterilization should be based on the risk of transmission, as related to the nature of contact with the patient (▶Table 6.1). ¹¹ Those instruments that enter the bloodstream or other sterile environments require sterilization between uses. Those that contact intact mucous membranes and do not normally penetrate sterile tissue require HLD, and those that contact intact skin require low-level disinfection.

**Table 6.1** Spaulding criteria for intensity of reprocessing of medical devices based on exposure risk ¹¹
Category	Definition	Reprocessing	Examples
Critical	Contact sterile tissue, including the vascular system	Sterilization	Surgical instruments Vascular and urinary catheters Endoscopic biopsy cables EUS needles, ERCP devices Endoscopes for intraoperative or transabdominal use
Semicritical	Contact intact mucous membranes or nonintact skin	High-level disinfection	GI endoscopes Respiratory therapy and anesthesia equipment Laryngoscope blades
Noncritical	Contact only intact skin	Low-level disinfection	Beds and rails Bedpans
Abbreviations: GI, gastrointestinal; ERCP, endoscopic retrograde cholangiopancreatography; EUS, endoscopic ultrasound.

6.2.2 Application to Gastrointestinal Endoscopes

By the Spaulding criteria, gastrointestinal endoscopes require HLD, in accord with their routine exposure to nonsterile mucous membranes. Endoscopes or devices that are used in sterile environments, such as percutaneous laparoscopic passage and insertion via an enterotomy during a laparotomy, are deemed to require sterilization. Devices breaking the mucosal surface, such as needles and biopsy cables, and those entering sterile systems such as the biliary tree or pancreatic ducts, must be sterilized between uses. Many busy endoscopy departments opt for use of sterile single-use accessories such as biopsy cables, sphincterotomes, and biliary guidewires to avoid the expense and organizational processes required for sterilizing inexpensive high-volume devices.

The most uniformly adopted approach to reprocessing of endoscopes employs several standardized steps (▶Table 6.2), ² , ³ , ⁴ , ⁵ , ⁶ , ⁷ including:

**Table 6.2** Steps in reprocessing of flexible endoscopes
Bedside (point-of-use) precleaning	Prior to transport to reprocessing room Manually wipe exterior surfaces with water and enzymatic detergent Aspirate or flush detergent through air/water and biopsy channels until clear	Removes visible soil and blood before drying and adherence Optimally reduces bioburden by 10 ³
Manual washing	Disassembly, followed by leak testing Full submersion of entire endoscope Manual washing and brushing of exterior with enzymatic solution Brushing and flushing of accessible channels Thorough water rinse	Optimally reduces bioburden by 10 ⁶
High-level disinfection	Automated preferable to manual Multiple machines and agents—require compatibility per IFUs Adhere to IFUs for minimum concentration and contact times	Optimally reduces bioburden by 10 ⁶ Narrow margin of safety primarily in complex instruments with elevators
Alcohol flushing	Usually an AER cycle Rinse of all LCG Alcohol flush to facilitate removal of water and full drying	Reduces risk of patient or personnel exposure Facilitates complete removal of water
Forced air drying	Filtered or “medical” air Often heated No fixed time/temperature parameters	Enhances microbial kill Prevents moist environment for proliferation of residual organisms during storage
Appropriate storage	Upright, dry, ventilated without exposure to ambient soiled atmosphere	Ensures clean, patient-ready endoscope at start of next procedure, calendar
Abbreviations: AER, automated endoscope reprocessors; IFUs, instructions for use; LCG, liquid chemical germicide.

Bedside precleaning (or “point-of-use processing”) using water and detergent to wipe the endoscope exterior and flushing or aspirating it through the air and water channels to remove grossly visible blood and soil before they have an opportunity to dry and more tightly adhere to the instrument. After this gross cleaning, disassembly of all valves and parts is performed, followed by leak testing.
Manual mechanical cleaning, distant from the bedside, with full submersion in water and detergent while physically wiping all exterior surfaces and brushing the accessible inner channels. This requires flushing and aspiration of large volumes of water and detergent followed by a thorough rinse. Detergents facilitate disaggregation and removal of debris but are not efficient microbicides. Some automated endoscope reprocessors (AERs) employ a validated “brushless” cleaning process prior to disinfection cycles.
HLD of all exposed surfaces via full submersion and perfusion through all lumens using an approved LCG and appropriate parameters for concentration, temperature, and duration of contact. HLD can be achieved with prolonged passive soaking in appropriate LCG solutions; however, data suggest greater shortfalls in meeting requisite parameters and greater risk of inadequate bacterial clearance. ¹²
Rinse with sterile or filtered water or tap water, followed by alcohol flush of all accessible channels (umbilical cord, biopsy, elevator cables) to evacuate residual LCG and water, thereby facilitating complete drying. This step is usually automated and accomplished by most AER machines.
Forced air drying to ensure complete removal of moisture from the endoscope channels.
Upright storage in clean, dry cabinets away from flow of ambient microorganisms. Straight upright storage theoretically facilitates drainage of any potentially retained liquids. Varieties of specialty cabinets with filtered or heated air flow, and some with flat storage, are marketed for this purpose.

HLD performed with careful adherence to validated manufacturers’ instructions for use (IFUs) results in clean endoscopes with remarkably low risk of residual clinically important contaminants. Adequate reprocessing of gastrointestinal endoscopes, however, is hampered by several specific challenges, including: (1) the immense bioburden they acquire during use, (2) the relatively narrow margin of safety achieved when all reprocessing steps are appropriately performed, (3) the risk for development of intractable biofilm when cleaning steps are insufficiently performed, (4) the lack of rapid and accurate bio-indicators of the process end points, (5) training, support, and ongoing supervision for staff who performs the repetitive tasks, and (6) the need for efficient turnaround of instruments in busy clinical environments.

Following use, endoscopes commonly harbor 10 ⁶ to 10 ⁹ microorganisms. Following combined precleaning and manual cleaning, endoscopes enter HLD with a bioburden of about 10 ¹ to 10 ⁵ microorganisms. ¹³ , ¹⁴ HLD achieves a further 6 log (10 ⁶ ) reduction, culminating in a theoretical terminal bioburden of 10^–6 to 10 ¹ organisms per instrument. ¹⁵ While this is generally well below the inoculum required for detrimental clinical effects, any shortcoming or hindrance to optimal performance clearly risks shortcomings in the terminal cleanliness and safety of the instrument. Failure of the initial precleaning and cleaning steps risks the development of adherent biofilm, which cannot be reliably removed or sterilized with repeated optimal performance of standard HLD. Reliable, inexpensive, rapid biomarkers to assess adequacy of reprocessing by assaying for residual contamination would clearly improve performance and cleaning outcomes. No such indicators exist, however. A variety of indicators for residual blood, protein, and other components of living tissue have been evaluated, but none appear reliable for assessment of the fully reprocessed instrument. ¹⁶ Testing for ATP, which is present in all living cells, is widely used in food preparation and cleaning industries, but ATP results obtained from reprocessed endoscopes do not correlate with terminal culture results. ¹⁷ Gross differences in ATP levels are evident between well-cleaned and poorly cleaned instruments, prior to HLD, so it may prove useful as a check on training and monitoring of performance by cleaning personnel. ¹⁸