Which of the following types of medical items requires sterilization if they are to be used during patient care?

Definition of Terms

Sterilization is defined as the complete elimination or destruction of all forms of microbial life and is accomplished in health care facilities through either physical or chemical processes. Steam under pressure, dry heat, ethylene oxide (ETO) gas, hydrogen peroxide gas plasma, vaporized hydrogen peroxide, hydrogen peroxide with ozone, and liquid chemicals are the principal sterilizing agents used in health care facilities. Sterilization is intended to convey an absolute meaning, not a relative one. Unfortunately, some health professionals and the technical and commercial literature refer to “disinfection” as “sterilization” and items as “partially sterile.” When chemicals are used for the purposes of destroying all forms of microbiologic life, including fungal and bacterial spores, they may be called chemical sterilants. These same germicides used for shorter exposure periods may also be part of the disinfection process (i.e., high-level disinfection).

Disinfection describes a process that eliminates many or all pathogenic microorganisms on inanimate objects, with the exception of bacterial spores. Disinfection is usually accomplished with the use of liquid chemicals or wet pasteurization in health care settings. The efficacy of disinfection is affected by a number of factors, each of which may nullify or limit the efficacy of the process. Some of the factors that affect both disinfection and sterilization efficacy are the prior cleaning of the object; the organic and inorganic load present; the type and level of microbial contamination; the concentration of and time of exposure to the germicide; the nature of the object (e.g., crevices, hinges, and lumens); the presence of biofilms; the temperature and pH during the disinfection process; and in some cases the relative humidity of the sterilization process (e.g., ETO).

By definition, then, disinfection differs from sterilization by its lack of sporicidal property, but this is an oversimplification. A few disinfectants will kill spores with prolonged exposure times (e.g., 3–12 hours) and are calledchemical sterilants. At similar concentrations but with shorter exposure periods (e.g., 12 minutes for 0.55% ortho-phthalaldehyde [OPA]) these same disinfectants will kill all microorganisms with the exception of large numbers of bacterial spores and are calledhigh-level disinfectants. Low-level disinfectants may kill most vegetative bacteria, some fungi, and some viruses in a practical period of time (<10 minutes), whereasintermediate-level disinfectants may be cidal for mycobacteria, vegetative bacteria, most viruses, and most fungi but do not necessarily kill bacterial spores. The germicides differ markedly among themselves primarily in their antimicrobial spectrum and rapidity of action.Table 299.1 will be discussed later and consulted in this context.

Cleaning, on the other hand, is the removal of visible soil (e.g., organic and inorganic material) and microbial contaminants from objects and surfaces, and it normally is accomplished by manual or mechanical means using water with detergents or enzymatic products. Thorough cleaning is essential before high-level disinfection and sterilization because inorganic and organic materials that remain on the surfaces of instruments interfere with the effectiveness of these processes. Also, if the soiled materials become dried or baked onto the instruments, the removal process becomes more difficult and the disinfection or sterilization process less effective or ineffective. Surgical instruments should be pretreated or rinsed to prevent drying of blood and to soften or remove blood from the instruments immediately or as soon as feasible after use. Treating contaminated instruments with alcohol, allowing instruments to soak in water for prolonged periods, or drying increases cleaning difficulty and should be discouraged.14Decontamination is a procedure that removes pathogenic microorganisms from objects so they are safe to handle, use, or discard.

Sterilization Overview

In-office sterilization of instruments between patients need not be a difficult or complicated process. A simplified description of the sterilization and disinfection options available quickly guides practitioners to the one that is most suitable for their dental offices (Table 32-3). A quick overview of the different sterilization cycles, their benefits and limitations, and their utility and operating times further guides decision making. Finally, the validation process provides confidence regarding sterilization to the dental professional and assurance to the dental staff and patients.

The guiding principles in sterilization, as in other dental areas, should be proven and demonstrable effectiveness in destroying pathogens, ease of use in a daily clinical setting, and practical efficiency.

Disinfection and Sterilization (SeeChapter 299)

Disinfection and sterilization of patient care equipment are a fundamental aspect of infection prevention in a hospital. The Spaulding classification for disinfection and sterilization is outlined inTable 298.1. Patients and health care personnel generally take for granted that medical instruments used for invasive procedures are appropriately disinfected or sterilized and represent the least of the patient's risk for postprocedure complications. Yet hospital disinfection and sterilization programs present many opportunities for errors and mishaps. For example, disinfection or sterilization can fail if visible organic or inorganic material is not first cleaned from instruments, reagents are expired and have lost potency, or biologic indicators are not used properly. Sizeable clonal outbreaks of multidrug-resistant bacteria in recent years have brought to light the frailties of high-level disinfection procedures for gastrointestinal endoscopes, particularly those used for biliary procedures. Some large outbreaks were traced to endoscopes that retained infectious material even after cleaning and disinfection according to published guidelines.15,16

1.2 Disinfection

Disinfection is defined as a procedure, the result of which is transient and that eliminates or kills microorganisms and/or deactivates undesirable viruses that are carried by inert contaminated environments. Such operations, which are carried out in accordance with defined objectives, relate solely to the microorganisms that are present at the time the procedure is carried out.

Disinfection is a generic term that refers to any antimicrobial measure (regardless of the level of the outcome attained), using a product that exhibits in-vitro properties that meet the criteria of a disinfectant or antiseptic agent. The name of each disinfection procedure should indicate its application domain, for example, medical device disinfection, floor disinfection, and hand disinfection.

Disinfection

Disinfection is defined broadly as the destruction of microorganisms, except bacterial spores, on inanimate objects (e.g., medical devices such as endoscopes). Three levels of disinfection are achievable depending on the amount and kind of microbial killing involved. These levels of disinfection are as follows:

High-level disinfection (HLD): the destruction of all viruses, vegetative bacteria, fungi, mycobacterium, and some, but not all, bacterial spores.32,33 For LCGs, HLD is operationally defined as the ability to kill 106 mycobacteria (a six-log reduction). The efficacy of HLD is dependent on several factors and includes the type and level of microbial contamination; effective precleaning of the endoscope; presence of biofilm; physical properties of the object; concentration, temperature, pH, and exposure time to the germicide; and drying after rinsing to avoid diluting the disinfectant.32

Intermediate-level disinfection: the destruction of all mycobacteria, vegetative bacteria, fungal spores, and some nonlipid viruses, but not bacterial spores.

Low-level disinfection: a process that can kill most bacteria (except mycobacteria or bacterial spores), most viruses (except some nonlipid viruses), and some fungi.

Although this categorization for disinfection levels generally remains valid, there are examples of disinfection issues with prions, viruses, mycobacteria, and protozoa that challenge these definitions.34

Antiseptics are chemicals intended to reduce or destroy microorganisms on living tissue (e.g., skin), as opposed to disinfectants, which are used on inanimate objects (e.g., medical devices such as endoscopes). The difference in the way the same chemical is used to achieve different levels of disinfection and sterilization is important for endoscopy because the contact times for sterilization with any given LCG are generally much longer (hours) than for high-level disinfection (minutes) and may be detrimental to the endoscope. The relative resistance of various microorganisms to LCGs is shown in Box 4.1.

Definitions

Disinfection, the desired result of field water treatment, means the removal or destruction of harmful microorganisms. Technically, it refers only to chemical means such as halogens, but the term can be applied to heat and filtration. Pasteurization is similar to disinfection but specifically refers to the use of heat, usually at temperatures below 100°C, to kill most pathogenic organisms. Disinfection and pasteurization should not be confused with sterilization, which is the destruction or removal of all life forms. The goal of disinfection is to achieve potable water, indicating that a water source, on average over a period of time, contains a ‘minimal microbial hazard’, so the statistical likelihood of illness is acceptable. Purification is the removal of organic or inorganic chemicals and particulate matter to remove offensive color, taste, and odor. It is frequently used interchangeably with disinfection (e.g., EPA classification of water purifier), but purification as used here may not remove or kill enough microorganisms to ensure microbiologic safety.

Definitions

Disinfection, the desired result of field water treatment, means the removal or destruction of harmful microorganisms. Technically, it refers only to chemical means such as halogens, but the term can be applied to heat and filtration.

Pasteurization is similar to disinfection but specifically refers to the use of heat, usually at temperatures below 212° F (100° C), to kill most enteric pathogenic organisms. Disinfection and pasteurization should not be confused with sterilization, which is the destruction or removal of all life forms. The goal of disinfection is to achieve potable water, indicating that a water source, on average over a period of time, contains a “minimal microbial hazard,” so the statistical likelihood of illness is minimized.

Purification is the removal of organic or inorganic chemicals and particulate matter to remove offensive color, taste, and odor. It is frequently used interchangeably with disinfection (e.g., Environmental Protection Agency [EPA] classification of water purifier), but purification, as used here, may not remove or kill enough microorganisms to ensure microbiologic safety.

Disinfection

Disinfection of impressions is a concern with respect to viral diseases such as hepatitis B, acquired immunodeficiency syndrome, and herpes simplex, because the viruses may be transferred to gypsum models and present a risk to dental laboratory and operating personnel.

All alginate impressions should be disinfected before pouring with gypsum to form a cast. The most common form of disinfection is spraying, but studies have shown that such impressions can be immersed in disinfectant also. The effect of disinfection in 1% sodium hypochlorite or 2% potentiated glutaraldehyde solutions on accuracy and surface quality has been measured after 10- to 30-minute immersion. Statistically significant dimensional changes were observed; however, the changes were on the order of 0.1% and the quality of the surface was not impaired. Such changes would be insignificant for clinical applications such as the preparation of study models and working casts. In another study, immersion disinfection of alginates demonstrated little effect on accuracy and surface quality, but it was shown that one alginate product was best immersed in iodophor and another brand in glyoxal glutaraldehyde. The effect of disinfection on agar impression materials has not been reported, but considering the similarity of the two hydrocolloids, similar recommendations are reasonable.

Disinfection, Sterilization, and Removal of Infectious Waste

Disinfection and sterilization as they relate to IPC have been reviewed,90 and the HICPAC/CDC developed comprehensive guidelines in 2008.91 Cleaning is the removal of all foreign material from surfaces and objects. This process is accomplished using soap and enzymatic products. Failure to remove all organic material from items before disinfection and sterilization reduces the effectiveness of these processes. Disinfection is a process that eliminates all forms of microbial life except the endospore. Disinfection usually requires liquid chemicals. Disinfection of an inanimate surface or object is affected adversely by the following: the presence of organic matter; a high level of microbial contamination; use of too dilute germicide; inadequate disinfection time; an object that can harbor microbes in protected cracks, crevices, and hinges; and pH and temperature.

Sterilization is the eradication of all forms of microbial life, including fungal and bacterial spores. Sterilization is achieved by physical and chemical processes such as steam under pressure, dry heat, ethylene oxide, and liquid chemicals. The Spaulding classification of patient care equipment as critical, semicritical, and noncritical items with regard to sterilization and disinfection is used by the CDC. Critical items require sterilization because they enter sterile body tissues and carry a high risk of causing infection if they are contaminated; semicritical items require disinfection because they may contact mucous membranes and nonintact skin; and noncritical items require routine cleaning because they come in contact only with intact skin. If noncritical items used on patients requiring Transmission-Based Precautions, especially Contact Precautions, must be shared, these items should be disinfected between uses. Guidelines for specific objects and specific disinfectants are published and updated by the CDC. Multiple published reports and manufacturers similarly recommend the use and reuse of objects with appropriate sterilization, disinfection, or cleaning recommendations. Recommendations in guidelines for reprocessing endoscopes to avoid contamination focus on training of personnel, meticulous manual cleaning, high-level disinfection followed by rinsing and air-drying, and proper storage.92 However, outbreaks of MDR GNB infections associated with exposure to duodenoscopes used for retrograde cholangiopancreatography that have been reprocessed according to recommendations suggest a need for new endoscope reprocessing technologies.51,93 These endoscopes have a complex design with long, narrow channels, crevices that are difficult to access with a cleaning brush, right-angle turns, and heavy microbial contamination following procedures. Until new methods are developed, meticulous adherence to recommended processes with enhancements should be followed. Medical devices that are designed for single use (e.g., specialized catheters, electrodes, biopsy needles) must be reprocessed by third parties or hospitals according to the guidance issued by the Food and Drug Administration (FDA) in August, 2000 with amendments in September, 2006; such reprocessors are considered and regulated as “manufacturers.” Available data show that single-use devices reprocessed according to the FDA regulatory requirements are as safe and effective as new devices.

Deficiencies in disinfection and sterilization leading to infection have resulted either from failure to adhere to scientifically based guidelines or failures in the disinfection or sterilization processes. When such failures are discovered, an investigation must be completed, including notification of patients and, in some cases, testing for infectious agents. A guidance document for risk assessment and communication to patients in such situations is published.94

Healthcare facility waste is all biologic or nonbiologic waste that is discarded and not intended for further use. Medical waste is material generated as a result of use with a patient, such as for diagnosis, immunization, or treatment, and it includes soiled dressings and intravenous tubing. Infectious waste is that portion of medical waste that potentially could transmit an infectious disease. Microbiologic waste, pathologic waste, contaminated animal carcasses, blood, and sharps are all examples of infectious waste. Methods of effective disposal of infectious waste include incineration, steam sterilization, drainage to a sanitary sewer, mechanical disinfection, chemical disinfection, and microwave treatment. State regulations guide the treatment and disposal of regulated medical waste. Recommendations are available for developing and maintaining a program within a facility for safe management of medical waste.95

Disinfection

Chemical disinfection consists of adding a disinfectant (generally a strong oxidant) to the water, which reacts with the organic matter and microbial organisms. Most frequent chemical disinfection compounds are chlorine dioxide, chlorine, and chloramines on one hand and ozone on the other hand. Depending of the water, the chemical disinfection efficiency can be lowered, for instance, at higher pH when using chlorine or with high organic matter concentrations. Byproducts originating from oxidative reactions can also be generated by chemical disinfection. Some may have adverse health effects.

Microorganisms adsorbed on particles are more resistant to chemical disinfection than free living organisms. Chemical disinfection is generally used as the primary microbial removal step and can be completed by another disinfection to ensure microbial quality during the distribution.

Efficiency of disinfection is defined using the Ct value which is defined as the product of disinfectant concentration (milligram per liter) and the contact time (min). Temperature and pH both influence the Ct value.

Chlorine is a strong disinfectant regarding vegetative bacteria in a range from 0.05 to 200 mg-min l−1 depending on the organic matter load. Chlorine dioxide is also a strong oxidant and disinfectant more effective than free chlorine at basic pH. Ct values for chlorine dioxide are less than 1 mg-min l−1 for most vegetative bacteria and viruses (Table 3).

Table 3. Ct values for virus disinfection

Source: Adapted from OEDC/WHO (2003) Assessing Microbial Safety of Drinking Water. London: Organization for Economic Co-operation and Development and the World Health Organization.

However, some parasites as Cryptosporidium are known to show high resistance to chlorine-based oxidation with Ct values of approximately 15 mg-min l−1 for Giardia cysts.

Ultraviolet light (UV) is also widely used for water treatment. UV lamps are placed in a flow-through contact compartment that is continuously operated. UV fluence corresponding to the UV light intensity and the contact time (function of water flow rate) directly impacts the disinfection efficiency.

Both flow patterns and the type of lamp (medium to low pressure mercury lamps) influence the removal of organisms. Inactivation of adenoviruses by UV treatment requires higher fluencies than that for other organisms (Table 4).

Table 4. UV fluence required for microorganisms removal

Source: Adapted from Smets P, Rietveld L, Hijnen W, Medema G, and Stentröm TH (2006) Efficacy of water treatment processes. Microrisk, Microbiological Risk Assessment: A Scientific Basis for Managing Drinking Water Safety from Source to Tap. EU Project.

In addition to disinfection, special attention should be paid to ensure the absence of recontamination posttreatment. Chlorine, for instance, is widely used to protect drinking water safety along the water supply to the point of use.