Contact: Toll-Free #(800)CDC-INFO or check CDC’s website at: www.cdc.gov
"Monitor sterilizers at least weekly by using a biological indicator with a matching control (i.e., biological indicator and control from same lot number)." Guidelines for infection control in dental health-care settings - 2003. Morbidity and Mortality Weekly Report (MMWR), 52(RR-17), 19 December 2003.

“Use a biological indicator for every sterilizer load that contains an implantable device…” Guidelines for infection control in dental health-care settings - 2003. Morbidity and Mortality Weekly Report (MMWR), 52(RR-17)(243-248) 19 December 2003.

"All sterilizers should be monitored at least once a week with commercial preparations of spores intended specifically for the type of sterilizer." Gamer JS, Favero MS. CDC guideline for hand washing and Hospital environment control 1985. Infection Control 7(231-43), 1986.

"The adequacy of sterilization cycles should be verified by the periodic use of spore - testing devices (e.g., weekly for most dental practices)." Recommended Infection-Control Practices for Dentistry, Morbidity and Mortality Weekly Report (MMWR), 35(237-42), 1986.

“Proper functioning of sterilization cycles should be verified by the periodic use (at least weekly) of biological indicators (i.e. spore tests). Heat sensitive chemical indicators (e.g. those that change color after exposure to heat) alone do not ensure adequacy of a sterilization cycle but may be used on the outside of each pack to identify packs that have been processed through the heating cycle. A simple and inexpensive method to confirm heat penetration to all instruments during each cycle is the use of a chemical indicator inside and in the center of either a load of unwrapped instruments or in each multiple instrument pack; this procedure is recommended for use in all dental practices. Instructions provided by the manufacturers of medical/dental instruments and sterilization devices should be followed closely.”

Recommended Infection-Control Practices for Dentistry, 1993. Morbidity and Mortality Weekly Report (MMWR), 41(RR-8), 28 May 1993.

“Steam and low temperature sterilizers (e.g., hydrogen peroxide gas plasma, peracetic acid) should be monitored at least weekly with the appropriate commercial preparation of spores. If a sterilizer is used frequently (e.g., several loads per day), daily use of biological indicators allows earlier discovery of equipment malfunctions or procedural errors and thus minimizes the extent of patient surveillance and product recall needed in the event of a positive biological indicator. Each load should be monitored if it contains implantable objects. If feasible, implantable items should not be used until the results of spore tests are known to be negative.” See www.cdc.gove, Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008

Central Instrument Processing Area

In dental health care settings, all instrument cleaning, disinfecting, and sterilizing should occur in a designated central processing area in order to more easily control quality and ensure safety. The instrument processing area should be physically divided into sections for 1) receiving, cleaning, and decontamination; 2) preparation and packaging; 3) sterilization; and 4) storage. This division is designed to contain contaminated items in an area designed specifically for cleaning, thus preventing contamination of the clean areas where packaging, sterilization, and storage of sterile items occurs. Reusable contaminated instruments and devices are received, sorted, and cleaned in the cleaning area. The packaging area is for inspecting, assembling, and packaging clean instruments in preparation for final processing. The sterilization and storage areas contain the sterilizers and related supplies, as well as incubators for analyzing spore tests, and can contain enclosed storage for sterile items and disposable (single-use) items. When it is not possible to have physical separation of these areas, clearly labeling each area (e.g., from contaminated to sterile) might be satisfactory if the personnel who process the instruments are trained in work practices to prevent contamination of clean areas.

Chemical indicators are one of the three critical devices for monitoring a sterilization process. They are designed to respond with a characteristic chemical or physical change to one or more of the physical conditions within the sterilizing chamber. Chemical indicators are intended to detect potential sterilization failures immediately that could result from incorrect packaging, incorrect loading of the sterilizer, or malfunctions of the sterilizer. The Association for the Advancement of Medical Instrumentation has defined five classes of chemical indicators: Class 1 (process indicator); Class 2 (Bowie-Dick test indicator); Class 3 (single-parameter indicator); Class 4 (multi-parameter indicator); and Class 5 (integrating indicator).

FDA defines a physical*/chemical sterilization process indicator (21 CFR 880.2800(b)) as: A device intended for use by a health care provider to accompany products being sterilized through a sterilization procedure and to monitor one or more parameters of the sterilization process. The adequacy of the sterilization conditions as measured by these parameters is indicated by a visible change in the device.

Compared to biological indicators:

In one study, chemical indicators were more likely than biological indicators to inaccurately indicate sterilization at marginal sterilization times (e.g., 2 minutes). Chemical indicators should be used in conjunction with biological indicators, but based on current studies should not replace them because they indicate sterilization at marginal sterilization time and because only a biological indicator consisting of resistant spores can measure the microbicidal killing power of the sterilization process.

Placement of chemical indicators:

Chemical indicators are affixed on the outside of each pack to show that the package has been processed through a sterilization cycle, but these indicators do not prove sterilization has been achieved. Preferably, a chemical indicator also should be placed on the inside of each pack to verify sterilant penetration. Chemical indicators usually are either heat-or chemical-sensitive inks that change color when one or more sterilization parameters (e.g., steam-time, temperature, and/or saturated steam; ETO-time, temperature, relative humidity and/or ETO concentration) are present. If the internal and/or external indicator suggests inadequate processing, the item should not be used. An air-removal test (Bowie-Dick Test – a Class 2 indicator) must be performed daily in an empty dynamic-air-removal sterilizer (e.g., prevacuum steam sterilizer) to ensure air removal.

IMPORTANT NOTE: The “pass” response of a chemical indicator does not prove the item accompanied by the indicator is necessarily sterile.

Indicators come in many different forms including on autoclave tape, labels, pouches, Bowie-Dick Tests and more

Chemical Vapor Sterilization
Chemical Vapor Sterilization process uses a solution of alcohol, water, and trace formaldehyde which is heated to produce an unsaturated vapor that must reach a specified temperature, pressure and exposure time in order to achieve sterility. Users should follow the sterilizer manufacturers’ strict guidelines for proper packaging, loading and operation of this type of sterilizer.

Cleaning is the removal of foreign material (e.g., soil, and organic material) from objects and is normally accomplished using water with detergents or enzymatic products. Thorough cleaning is required 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 soiled materials dry or bake onto the instruments, the removal process becomes more difficult and the disinfection or sterilization process less effective or ineffective. Surgical instruments should be presoaked or rinsed to prevent drying of blood and to soften or remove blood from the instruments.

Manual cleaning is done in use areas without mechanical units (e.g., ultrasonic cleaners or washer-disinfectors) or for fragile or difficult-to-clean instruments. With manual cleaning, the two essential components are friction and fluidics. Friction (e.g., rubbing/scrubbing the soiled area with a brush) is an old and dependable method. Fluidics (i.e., fluids under pressure) is used to remove soil and debris from internal channels after brushing and when the design does not allow passage of a brush through a channel. When a washer-disinfector is used, care should be taken in loading instruments: hinged instruments should be opened fully to allow adequate contact with the detergent solution; stacking of instruments in washers should be avoided; and instruments should be disassembled as much as possible. For more detail on manual cleaning, see The Center For Disease Controls “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008” at www.cdc.gov.

Cleaning - Mechnically
Cleaning is the removal of foreign material (e.g., soil, and organic material) from objects and is normally accomplished using water with detergents or enzymatic products. Thorough cleaning is required 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. Mechanical Cleaning is the preferred method to cleaning instruments or devices – known to be 16 times more effective then cleaning manually.

The most common types of mechanical or automatic cleaners are ultrasonic cleaners, washer-decontaminators, washer-disinfectors, and washer-sterilizers.

Ultrasonic cleaning removes soil by cavitation and implosion in which waves of acoustic energy are propagated in aqueous solutions to disrupt the bonds that hold particulate matter to surfaces. Bacterial contamination can be present in used ultrasonic cleaning solutions (and other used detergent solutions) because these solutions generally do not make antibacterial label claims. Even though ultrasound alone does not significantly inactivate bacteria, sonication can act synergistically to increase the cidal efficacy of a disinfectant. Users of ultrasonic cleaners should be aware that the cleaning fluid could result in endotoxin contamination of surgical instruments, which could cause severe inflammatory reactions.

Washer-sterilizers are modified steam sterilizers that clean by filling the chamber with water and detergent through which steam passes to provide agitation. Instruments are subsequently rinsed and subjected to a short steam-sterilization cycle. Another washer-sterilizer employs rotating spray arms for a wash cycle followed by a steam sterilization cycle at 285°F.

Washer-decontaminators/disinfectors act like a dishwasher that uses a combination of water circulation and detergents to remove soil. These units sometimes have a cycle that subjects the instruments to a heat process (e.g., 93°C for 10 minutes). Washer-disinfectors are generally computer-controlled units for cleaning, disinfecting, and drying solid and hollow surgical and medical equipment.

See the complete recommendations on cleaning, disinfection and sterilization at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

Automated cleaning and rinsing process utilize equipment such as: Utensil or cart washers, washer-sterilizer, pasteurization equipment, washer-disinfectors, or washer-sanitizers. Considerations in selecting cleaning methods and equipment include their effectiveness, their compatibility with the items to be cleaned, and the occupational health and exposure risks they pose. Some are made to clean specific devices, such as endoscopes. It is recommended that the manufacturer’s instruction manual of the cleaning equipment be followed for maximum effectiveness and to avoid unnecessary damage to the devices being cleaned.

Ultrasonic cleaners are used to do fine-cleaning of complex instruments, removing soil from joints, crevices, lumens and other difficult to clean areas. This process is done only after removal of heavy soil using equipment mentioned above, or by manual cleaning. Ultrasonic cleaning does not disinfect or sterilize. The cleaning solution for ultrasonic cleaners should be changed before it becomes heavily soiled, minimizing the risk of cross-contamination. Not all devices can be intermixed in the ultrasonic cleaning process. The manufacturer of the device should specify any restrictions.

See the complete recommendations on cleaning, disinfection and sterilization at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

The effectiveness of a disinfection procedure is controlled significantly by a number of factors, each one of which may have a pronounced effect on the end result. Among these are:

• the nature and number of contaminating microorganisms (especially the presence of bacterial spores);

• the amount of organic matter present (e.g., soil, feces, and blood);

• the type and condition of instruments, devices, and materials to be disinfected;

• the temperature.

Disinfection is a procedure that reduces the level of microbial contamination, but there is a broad range of activity that extends from sterility at one extreme to a minimal reduction in the number of microbial contaminants at the other. By definition, chemical disinfection and in particular, high-level disinfection differs from chemical sterilization by its lack of sporicidal power. This is an over simplification of the actual situation because a few chemical germicides used as disinfectants do, in fact, kill large numbers of spores even though high concentrations and several hours of exposure may be required. Non-sporicidal disinfectants may differ in their capacity to accomplish disinfection or decontamination. Some germicides rapidly kill only the ordinary vegetative forms of bacteria such as staphylococci and streptococci, some forms of fungi, and lipid containing viruses, whereas others are effective against such relatively resistant organisms as Mycobacterium tuberculosis var. bovis, non-lipid viruses, and most forms of fungi.

Many disinfectants are used alone or in combinations (e.g., hydrogen peroxide and peracetic acid) in the health-care setting. These include alcohols, chlorine and chlorine compounds, formaldehyde, glutaraldehyde, ortho-phthalaldehyde, hydrogen peroxide, iodophors, peracetic acid, phenolics, and quaternary ammonium compounds. Commercial formulations based on these chemicals are considered unique products and must be registered with EPA or cleared by FDA. In most instances, a given product is designed for a specific purpose and is to be used in a certain manner. Therefore, users should read labels carefully to ensure the correct product is selected for the intended use and applied efficiently. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

Distilled Water
Distilled water is water heated to boiling point, vaporized, cooled, condensed, and collected so that no impurities are reintroduced.

Most sterilizer manufacturers require that distilled water is used for steam sterilizers. Using tap water will adversely affect the quality of the steam and cause sterilization failures and possibly damage the sterilizer itself. ATS, Inc. offers quality water distillers allowing you to distill your own tap water.

Advantages in buying a water distiller:

1. No longer need to transport heavy gallons of distilled water!

2. Store-bought distilled water costs average of $1.20 versus tap water costs 10-15¢ per gallon.

3. IT’S HEALTHY FOR YOU TOO – not just for your sterilizer! Distilled water is great drinking water as it is PURE water - all impurities are boiled off.

Dry Heat Sterilizers
Dry Heat sterilization should be used only for materials that might be damaged by moist heat or that are impenetrable to moist heat (e.g., powders, petroleum products, sharp instruments). The primary lethal process is considered to be oxidation of cell constituents. The most common time-temperature relationships for sterilization with hot air sterilizers are 170°C (340°F) for 60 minutes, 160°C (320°F) for 120 minutes, and 150°C (300°F) for 150 minutes.

Advantages and Disadvantages of Dry Heat Sterilization:

The advantages for dry heat include the following: it is nontoxic and does not harm the environment; a dry heat cabinet is easy to install and has relatively low operating costs; it penetrates materials; and it is noncorrosive for metal and sharp instruments. The disadvantages for dry heat are the slow rate of heat penetration and microbicidal killing makes this a time-consuming method. In addition, the high temperatures are not suitable for most materials.

Two Types of Dry Heat Sterilizers:

There are two types of dry-heat sterilizers: the static-air type and the forced-air type. The static-air type is referred to as the oven-type sterilizer as heating coils in the bottom of the unit cause the hot air to rise inside the chamber via gravity convection. This type of dry-heat sterilizer is much slower in heating, requires longer time to reach sterilizing temperature, and is less uniform in temperature control throughout the chamber than is the forced-air type. The forced-air or mechanical convection sterilizer is equipped with a motor-driven blower that circulates heated air throughout the chamber at a high velocity, permitting a more rapid transfer of energy from the air to the instruments. ATS, Inc. offers a quality line of Dry Heat sterilizers – compare our prices!

Spore Testing Dry Heat Sterilizers:

Bacillus atrophaeus spores should be used to monitor the sterilization process for dry heat because they are more resistant to dry heat than are Geobacillus stearothermophilus spores.

Autoclave Testing Service, Inc. spore tests all sterilizers, not just autoclaves (steam sterilizers). For spore testing Dry Heat sterilizers, the microbiology laboratory uses Bacillus atrophaeus spores which are cultured at 35°C. We offer immediate notification of positive tests (spores that show growth indicating sterilizer failure). Most failed tests show up within 24 to 48 hours and you will be immediately notified. ATS, Inc. is also a supplier of Dry Heat sterilizers – see New or Used sterilizers.

Ethylene Oxide Sterilization
Ethylene Oxide sterilization is a low temperature sterilization process designed to sterilize instruments or devices that are sensitive to heat and/or moisture. ETO is a colorless gas that is flammable and explosive. The four essential parameters (operational ranges) are: gas concentration (450 to 1200 mg/l); temperature (37 to 63°C); relative humidity (40 to 80%) (water molecules carry ETO to reactive sites); and exposure time (1 to 6 hours). These influence the effectiveness of ETO sterilization. Within certain limitations, an increase in gas concentration and temperature may shorten the time necessary for achieving sterilization.

The basic ETO sterilization cycle consists of five stages (i.e., preconditioning and humidification, gas introduction, exposure, evacuation, and air washes) and takes approximately 2-1/2 hrs excluding aeration time. Mechanical aeration for 8 to 12 hours at 50 to 60°C allows desorption of the toxic ETO residual contained in exposed absorbent materials. Most modern ETO sterilizers combine sterilization and aeration in the same chamber as a continuous process. These ETO models minimize potential ETO exposure during door opening and load transfer to the aerator. Ambient room aeration also will achieve desorption of the toxic ETO but requires 7 days at 20°C. There are no federal regulations for ETO sterilizer emission; however, many states have promulgated emission-control regulations.

Microbicidal Activity:

The excellent microbicidal activity of ETO has been demonstrated in several studies and summarized in published reports. ETO inactivates all microorganisms although bacterial spores (especially Bacillus atrophaeus) are more resistant than other microorganisms. For this reason B. atrophaeus is the recommended biological indicator. Like all sterilization processes, the effectiveness of ETO sterilization can be altered by lumen length, lumen diameter, inorganic salts, and organic materials. For example, although ETO is not used commonly for reprocessing endoscopes, several studies have shown failure of ETO in inactivating contaminating spores in endoscope channels or lumen test units and residual ETO levels averaging 66.2 ppm even after the standard degassing time. Failure of ETO also has been observed when dental handpieces were contaminated with Streptococcus mutans and exposed to ETO. It is recommended that dental handpieces be steam sterilized.

Uses:

ETO is used in healthcare facilities to sterilize critical items (and sometimes semi-critical items) that are moisture or heat sensitive and cannot be sterilized by steam sterilization. The use of ETO evolved when few alternatives existed for sterilizing heat- and moisture-sensitive medical devices; however, favorable properties account for its continued widespread use. Two ETO gas mixtures are available to replace ETO-chlorofluorocarbon (CFC) mixtures for large capacity, tank-supplied sterilizers. The ETO-carbon dioxide (CO2) mixture consists of 8.5% ETO and 91.5% CO2. This mixture is less expensive than ETO-hydro chlorofluorocarbons (HCFC), but a disadvantage is the need for pressure vessels rated for steam sterilization, because higher pressures (28-psi gauge) are required. The other mixture, which is a drop-in CFC replacement, is ETO mixed with HCFC.

Following the sterilization cycle:

ETO is absorbed by many materials. For this reason, following sterilization the item must undergo aeration to remove residual ETO. Guidelines have been promulgated regarding allowable ETO limits for devices that depend on how the device is used, how often, and how long in order to pose a minimal risk to patients in normal product use.

Disadvantages / hazardous:

The main disadvantages associated with ETO are the lengthy cycle time, the cost, and its potential hazards to patients and staff; the main advantage is that it can sterilize heat- or moisture-sensitive medical equipment without deleterious effects on the material used in the medical devices. Acute exposure to ETO may result in irritation (e.g., to skin, eyes, gastrointestinal or respiratory tracts) and central nervous system depression. Chronic inhalation has been linked to the formation of cataracts, cognitive impairment, neurologic dysfunction, and disabling polyneuropathies. Occupational exposure in healthcare facilities has been linked to hematologic changes and an increased risk of spontaneous abortions and various cancers. ETO should be considered a known human carcinogen.

Damaging to ozone:

HCFCs are approximately 50-fold less damaging to the earth’s ozone layer than are CFCs. The EPA will begin regulation of HCFC in the year 2015 and will terminate production in the year 2030. Two companies provide ETO-HCFC mixtures as drop-in replacement for CFC-12; one mixture consists of 8.6% ETO and 91.4% HCFC, and the other mixture is composed of 10% ETO and 90% HCFC. An alternative to the pressurized mixed gas ETO systems is 100% ETO. The 100% ETO sterilizers using unit-dose cartridges eliminate the need for external tanks.

ETO Exposure:

ETO toxicity has been established in a variety of animals. Exposure to ETO can cause eye pain, sore throat, difficulty breathing and blurred vision. Exposure can also cause dizziness, nausea, headache, convulsions, blisters and vomiting and coughing. In a variety of in vitro and animal studies, ETO has been demonstrated to be carcinogenic. ETO has been linked to spontaneous abortion, genetic damage, nerve damage, peripheral paralysis, muscle weakness, and impaired thinking and memory. Occupational exposure in healthcare facilities has been linked to an increased risk of spontaneous abortions and various cancers. Injuries (e.g., tissue burns) to patients have been associated with ETO residues in implants used in surgical procedures. Residual ETO in capillary flow dialysis membranes has been shown to be neurotoxic in vitro. OSHA has established a PEL of 1 ppm airborne ETO in the workplace, expressed as a TWA for an 8-hour work shift in a 40-hour work week. The “action level” for ETO is 0.5 ppm, expressed as an 8-hour TWA, and the short-term excursion limit is 5 ppm, expressed as a 15-minute TWA. Several personnel monitoring methods (e.g., charcoal tubes and passive sampling devices) are in use. OSHA has established a PEL of 5 ppm for ethylene chlorohydrin (a toxic by-product of ETO) in the workplace. Additional information regarding use of ETO in health care facilities is available from NIOSH. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

A storage practice that recognizes that a package and its contents should remain sterile until some event causes the item(s) to become contaminated.

Although some hospitals continue to date every sterilized product and use the time-related shelf-life practice, many hospitals have switched to an event-related shelf-life practice. This latter practice recognizes that the product should remain sterile until some event causes the item to become contaminated (e.g., tear in packaging, packaging becomes wet, seal is broken). Event-related factors that contribute to the contamination of a product include bioburden (i.e., the amount of contamination in the environment), air movement, traffic, location, humidity, insects, vermin, flooding, storage area space, open/closed shelving, temperature, and the properties of the wrap material.

There is data that support the event-related shelf-life practice; one study examined the effect of time on the sterile integrity of paper envelopes, peel pouches, and nylon sleeves. The most important finding was the absence of a trend toward an increased rate of contamination over time for any pack when placed in covered storage. Another evaluated the effectiveness of event-related outdating by microbiologically testing sterilized items. During the 2-year study period, all of the items tested were sterile. Thus, contamination of a sterile item is event-related and the probability of contamination increases with increased handling. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

1. Clean the item before placing it in the sterilizing container (that are FDA cleared for use with flash sterilization) or tray;
2. Prevent exogenous contamination of the item during transport from the sterilizer to the patient;
3. Monitor sterilizer function with mechanical, chemical, and biologic monitors.

EXCEPTION: Do not flash sterilize implanted surgical devices unless doing so is unavoidable. Do not use flash sterilization for convenience, as an alternative to purchasing additional instrument sets, or to save time. Do not use packaging materials and containers in flash sterilization cycles unless the sterilizer and the packaging material/container are designed for this use.

When necessary, use flash sterilization for patient-care items that will be used immediately (e.g., to reprocess an inadvertently dropped instrument). Also, when necessary, use flash sterilization for processing patient-care items that cannot be packaged, sterilized, and stored before use. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

Weekly testing is minimum:

Steam and low temperature sterilizers (e.g., hydrogen peroxide gas plasma, peracetic acid) should be monitored at least weekly with the appropriate commercial preparation of Geobacillus stearothermophilus spores. If a sterilizer is used frequently (e.g., several loads per day), daily use of biological indicators allows earlier discovery of equipment malfunctions or procedural errors and thus minimizes the extent of patient surveillance and product recall needed in the event of a positive biological indicator. Each load should be monitored if it contains implantable objects. If feasible, implantable items should not be used until the results of spore tests are known to be negative. See also www.cdc.gov/oralhealth/infectioncontrol/faq/steri...

Originally, spore-strip biological indicators required up to 7 days of incubation to detect viable spores from marginal cycles (i.e., when few spores remained viable). The next generation of biological indicator was self-contained in plastic vials containing a spore-coated paper strip and a growth media in a crushable glass ampoule. This indicator had a maximum incubation of 48 hours but significant failures could be detected in ≤24 hours. A rapid-readout biological indicator that detects the presence of enzymes of Geobacillus stearothermophilus by reading a fluorescent product produced by the enzymatic breakdown of a non-fluorescent substrate has been marketed for the more than 10 years. Studies demonstrate that the sensitivity of rapid-readout tests for steam sterilization (1 hour for 132°C gravity sterilizers, 3 hrs for 121°C gravity and 132°C vacuum sterilizers) parallels that of the conventional sterilization-specific biological indicators and the fluorescent rapid readout results reliably predict 24 and 48-hour and 7-day growth. The rapid-readout biological indicator is a dual indicator system as it also detects acid metabolites produced during growth of the Geobacillus stearothermophilus spores. This system is different from the indicator system consisting of an enzyme system of bacterial origin without spores. Independent comparative data using suboptimal sterilization cycles (e.g., reduced time or temperature) with the enzyme-based indicator system have not been published. ATS, Inc. also has a rapid readout system available – see Biological Indicators.

Germicide
Germicide is an agent that destroys microorganisms, especially pathogenic organisms. Other terms with the suffix "–cide" (e.g., virucide, fungicide, bactericide, tuberculocide, sporicide) are agents that destroy the microorganism noted in the prefix. Germicides may be used to inactivate microorganisms in or on living tissue (antiseptic) or on environmental surfaces (disinfectants).
Huck Towel
Huck towel is an all-cotton surgical towel with a honey-comb weave; both warp and fill yarns are tightly twisted. Huck towels can be used to prepare biological indicator challenge test packs (or PCD’s).

Implantable Device
According to the Food and Drug Administration (FDA), "device that is placed into a surgically or naturally formed cavity of the human body if it is intended to remain there for a period of 30 days or more" [21 CFR 812.3(d)].

Mechanical Indicator
Mechanical indicators are devices such as gauges, meter, display, or printout from a sterilizer display an element of the sterilization process (e.g., time, temperature, pressure). This is of the three parameters required to monitor sterilizer cycles. Internal and external chemical indicators and biological indicators are to be used along with mechanical monitoring of sterilizer, to ensure sterilization is being reached in every cycle.

Microbiocidal

MECHANICAL INDICATOR Microbicidal methods (lethal kill of microorganisms) include disinfection or sterilization by thermal or chemical means. This is the final step in the decontamination process. Knowledge is critical in selecting the correct microbicidal process as it depends on the device manufacturers’ recommendations, the manufacturer of the disinfectant solution and what the device has been exposed to. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

Microorganism Disinfection and Sterilization
Thorough cleaning required before disinfection and sterilization:
All other conditions remaining constant, the larger the number of microbes, the more time a germicide needs to destroy all of them. Spaulding illustrated this relation when he employed identical test conditions and demonstrated that it took 30 minutes to kill 10 Bacillus atrophaeus (formerly Bacillus subtilis) spores but 3 hours to kill 100,000 Bacillus atrophaeus spores. This reinforces the need for scrupulous cleaning of medical instruments before disinfection and sterilization. Reducing the number of microorganisms that must be inactivated through meticulous cleaning, increases the margin of safety when the germicide is used according to the labeling and shortens the exposure time required to kill the entire microbial load. Accessibility of sterilant to microorganisms:
The location of microorganisms also must be considered when factors affecting the efficacy of germicides are assessed. Medical instruments with multiple pieces must be disassembled and equipment such as endoscopes that have crevices, joints, and channels are more difficult to disinfect than are flat-surface equipment because penetration of the disinfectant of all parts of the equipment is more difficult. Only surfaces that directly contact the germicide will be disinfected, so there must be no air pockets and the equipment must be completely immersed for the entire exposure period. Manufacturers should be encouraged to produce equipment engineered for ease of cleaning and disinfection. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.
Packaging
Thorough cleaning required before disinfection and sterilization: All other conditions remaining constant, the larger the number of microbes, the more time a germicide needs to destroy all of them. Spaulding illustrated this relation when he employed identical test conditions and demonstrated that it took 30 minutes to kill 10 Bacillus atrophaeus (formerly Bacillus subtilis) spores but 3 hours to kill 100,000 Bacillus atrophaeus spores. This reinforces the need for scrupulous cleaning of medical instruments before disinfection and sterilization. Reducing the number of microorganisms that must be inactivated through meticulous cleaning, increases the margin of safety when the germicide is used according to the labeling and shortens the exposure time required to kill the entire microbial load. Accessibility of sterilant to microorganisms: The location of microorganisms also must be considered when factors affecting the efficacy of germicides are assessed. Medical instruments with multiple pieces must be disassembled and equipment such as endoscopes that have crevices, joints, and channels are more difficult to disinfect than are flat-surface equipment because penetration of the disinfectant of all parts of the equipment is more difficult. Only surfaces that directly contact the germicide will be disinfected, so there must be no air pockets and the equipment must be completely immersed for the entire exposure period. Manufacturers should be encouraged to produce equipment engineered for ease of cleaning and disinfection. See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

Peracetic Acid Sterilization
Peracetic acid is a highly biocidal oxidizer that maintains its efficacy in the presence of organic soil. Peracetic acid removes surface contaminants (primarily protein) on endoscopic tubing. An automated machine using peracetic acid to sterilize medical, surgical, and dental instruments chemically (e.g., endoscopes, arthroscopes) was introduced in 1988. This microprocessor-controlled, low-temperature sterilization method is commonly used in the United States. The sterilant, 35% peracetic acid, and an anticorrosive agent are supplied in a single-dose container. The container is punctured at the time of use, immediately prior to closing the lid and initiating the cycle. The concentrated peracetic acid is diluted to 0.2% with filtered water (0.2 μm) at a temperature of approximately 50°C. The diluted peracetic acid is circulated within the chamber of the machine and pumped through the channels of the endoscope for 12 minutes, decontaminating exterior surfaces, lumens, and accessories.

Interchangeable trays are available to permit the processing of up to three rigid endoscopes or one flexible endoscope. Connectors are available for most types of flexible endoscopes for the irrigation of all channels by directed flow. Rigid endoscopes are placed within a lidded container, and the sterilant fills the lumens either by immersion in the circulating sterilant or by use of channel connectors to direct flow into the lumen(s). The peracetic acid is discarded via the sewer and the instrument rinsed four times with filtered water. Concern has been raised that filtered water may be inadequate to maintain sterility. Limited data have shown that low-level bacterial contamination may follow the use of filtered water in an AER but no data has been published on AERs using the peracetic acid system. Clean filtered air is passed through the chamber of the machine and endoscope channels to remove excess water. As with any sterilization process, the system can only sterilize surfaces that can be contacted by the sterilant.

The manufacturers suggest the use of biological monitors (Geobacillus stearothermophilus spore strips) both at the time of installation and routinely to ensure effectiveness of the process. The manufacturer’s clip must be used to hold the strip in the designated spot in the machine as a broader clamp will not allow the sterilant to reach the spores trapped under it. One investigator reported a 3% failure rate when the appropriate clips were used to hold the spore strip within the machine. The use of biological monitors designed to monitor either steam sterilization or ETO for a liquid chemical sterilizer has been questioned for several reasons including spore wash-off from the filter paper strips which may cause less valid monitoring. The processor is equipped with a conductivity probe that will automatically abort the cycle if the buffer system is not detected in a fresh container of the peracetic acid solution. A chemical monitoring strip that detects that the active ingredient is >1500 ppm is available for routine use as an additional process control.

Microbicidal Activity. Peracetic acid will inactivate gram-positive and gram-negative bacteria, fungi, and yeasts in <5 minutes at <100 ppm. In the presence of organic matter, 200-500 ppm is required. For viruses, the dosage range is wide (12-2250 ppm), with poliovirus inactivated in yeast extract in 15 minutes with 1500 to 2250 ppm. Bacterial spores in suspension are inactivated in 15 seconds to 30 minutes with 500 to 10,000 ppm (0.05 to 1%).

Uses. This automated machine is used to chemically sterilize medical (e.g., GI endoscopes) and surgical (e.g., flexible endoscopes) instruments in the United States. Lumened endoscopes must be connected to an appropriate channel connector to ensure that the sterilant has direct contact with the contaminated lumen.

See the complete recommendations on sterilizer and disinfection at www.cdc.gov “Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008”.

Process Challenge Device
Process challenge device (or PCD) is an item designed to simulate product to be sterilized and to constitute a defined challenge to the sterilization process and used to assess the effective performance of the process. A PCD is a challenge test pack or test tray that contains a biologic indicator, a Class 5 integrating indicator, or an enzyme-only indicator.

The size and composition of the biological indicator test pack should be standardized to create a significant challenge to air removal and sterilant penetration and to obtain interpretable results. There is a standard 16-towel pack recommended by AAMI for steam sterilization consisting of 16 clean, preconditioned, reusable huck or absorbent surgical towels each of which is approximately 16 inches by 26 inches. Each towel is folded lengthwise into thirds and then folded widthwise in the middle. One or more biological indicators are placed between the eighth and ninth towels in the approximate geometric center of the pack. When the towels are folded and placed one on top of another, to form a stack (approximately 6 inch height) it should weigh approximately 3 pounds and should have a density of approximately 11.3 pounds per cubic foot. This test pack has not gained universal use as a standard pack that simulates the actual in-use conditions of steam sterilizers.

Commercially available disposable BI test packs that have been shown to be equivalent to the AAMI 16 towel test pack also may be used. The test pack should be placed flat in an otherwise fully loaded sterilizer chamber, in the area least favorable to sterilization (i.e., the area representing the greatest challenge to the biological indicator). This area is normally in the front, bottom section of the sterilizer, near the drain. A control biological indicator from the lot used for testing should be left unexposed to the sterilant, and then incubated to verify the pre-sterilization viability of the test spores and proper incubation. The most conservative approach would be to use a control for each run; however, less frequent use may be adequate (e.g., weekly).