Inadequate disinfection and sterilization of medical and dental items can lead to the persistence of infectious agents on surfaces and instruments. Some common areas of mistake are not cleaning the surface or instrument thoroughly before disinfection or sterilization, insufficient contact time of the disinfectant or sterilant and utilizing incorrect disinfectants.
Prevention is key, healthcare facilities must implement standardized protocols in disinfection and sterilization. Therefore, staff must be trained in these protocols and the disinfection and sterilization processes. Staff must be trained in the correct disinfectants to be used on various pathogens, and the contact time of the disinfectants. These can be different, depending on the intended pathogen to kill. Staff must also understand the importance of cleaning the surfaces first before disinfection.
It is important to note the difference between disinfection and sterilization. Disinfection is the process of eliminating pathogenic microorganisms. This process doesn’t kill spores. The goal of disinfection is to kill most disease-causing microorganisms, but not bacterial spores. A surface can be “highly disinfected” but still host resilient microbes. Common methods of disinfection include liquid chemicals such as iodophors, hydrogen peroxide, glutaraldehyde or alcohol. Disinfection is used on surfaces such as bracket trays in dentistry, counter tops, and bed rails in healthcare facilities.
The Centers for Disease Control (CDC) categorizes disinfectants into three categories: low, intermediate and high.
The Environmental Protection Agency (EPA) registers disinfectants as limited, broad-spectrum, or hospital products. Compared with CDC categories, an EPA-registered hospital disinfectant generally falls under low-level disinfection. These products are broad-spectrum and effective against some bacteria and viruses, but they do not kill Mycobacterium tuberculosis. Disinfectants with a tuberculocidal claim fall under the CDC’s intermediate-level category because they kill Mycobacterium tuberculosis, viruses, fungi, and bacteria.
Clinical contact surfaces are environmental surfaces that may become contaminated during patient care and require appropriate disinfection when visibly soiled with blood. In these cases, an intermediate-level disinfectant should be used, and the surface must remain wet for the full contact time listed in the manufacturer’s instructions for use. Because blood and other organic material can reduce disinfectant effectiveness, the process should include both precleaning and disinfection. If the product has a tuberculocidal claim, the labeled contact time for that claim should be followed during the disinfection step.
When used according to the manufacturer’s directions for high-level disinfection, immersion disinfectants can kill Mycobacterium tuberculosis, viruses, fungi, vegetative bacteria, and some bacterial endospores. High-level disinfection is appropriate for reusable semi-critical items that cannot tolerate heat sterilization. To ensure effective disinfection or sterilization, healthcare personnel must carefully follow the manufacturer’s instructions for use.
Sterilization is the complete destruction or removal of all forms of microbial life, including highly resistant bacterial spores. In other words, it means to free an object of life of any kind. Unlike disinfection, sterilization is an absolute process: an instrument is either sterile, or it is not. Common sterilization methods include high-pressure steam (autoclaving), dry heat, ethylene oxide gas, and liquid chemical sterilant. Sterilization is required for all critical items used in patient care.
Bacterial spores are difficult to destroy because they have a tough protective outer layer that helps them survive harsh conditions. Examples include spores produced by Clostridioides difficile and Bacillus anthracis, the bacterium that causes anthrax. Standard disinfectants typically cannot penetrate this protective layer. Effective destruction of bacterial spores usually requires heat sterilization or an appropriate high-level chemical sterilant used exactly as directed, often with an extended contact time.
Most healthcare devices are made from heat-stable materials and can therefore be processed using steam sterilization. Other sterilization methods include ethylene oxide gas and dry heat. Steam sterilization uses moist heat in the form of saturated steam under pressure and is the most widely used and reliable method. It is nontoxic, inexpensive, rapidly microbicidal and sporicidal, and able to quickly heat and penetrate fabrics. Although steam sterilization has many advantages, it also has limitations, including the potential for burns, corrosion, dulling, and rusting of some instruments.
The two most used steam sterilizers are gravity displacement sterilizers and pre-vacuum sterilizers. In gravity displacement sterilizers, steam enters the chamber and forces unsaturated air out through a vent in the chamber wall. This method requires a 30-minute exposure time at 121°C. The second method, the pre-vacuum sterilizer, is fitted with a vacuum pump that creates a vacuum in the chamber to ensure air removal from both the sterilizing chamber and the load before the chamber is pressurized with steam. This method improves the speed and efficiency of the sterilization process and requires a 4-minute exposure time at 132°C. With both of these methods, always use FDA-approved devices and follow manufacturer’s instructions for proper use.
Dry heat sterilizers transfer heat energy from the air inside the oven to the instruments. Because dry heat lacks vapor pressure, higher temperatures are required to achieve sterilization. Dry heat is appropriate for items that may dull or rust in an autoclave, as well as items such as powders, cellulose, or ink that require sterilization. However, the packaging used for dry heat sterilization must be able to withstand high temperatures to prevent accidental fire or charring of contents inside the sterilizer. These also must be FDA-approved devices and manufacturer’s instructions must be followed.
Now that the difference between disinfection and sterilization has been established, it is important to determine which items require disinfection and which require sterilization. E.H. Spaulding, a microbiologist, developed a classification system for instruments in 1939 that is still widely used in healthcare. His system states that the way an instrument is used determines how it must be processed. This classification system places instruments and items into three categories: critical, semi-critical, and non-critical.
Critical items are those that contact sterile tissue, enter or penetrate normally sterile tissue, or enter the vascular system. These items carry a high risk of infection or disease transmission if handled improperly. Critical items must be sterilized between each use. If an item cannot be sterilized, it should be considered single-use. Examples of critical items in healthcare include scalpels, forceps, retractors, and needles. Examples in dentistry include hygiene scalers, periodontal scalers, and burs.
Semi-critical items are those that contact mucous membranes or non-intact skin. These items also carry a risk of infection transmission if they are not handled properly. The CDC notes that if a semi-critical item is heat stable, it should be heat sterilized. If it cannot be heat sterilized, it should be high-level disinfected or considered a single-use item. The goal for semi-critical items is to remove all microorganisms except high numbers of bacterial spores. Examples of semi-critical items in healthcare include endoscopes and vaginal speculums. In dentistry, semi-critical items include handpieces and mouth mirrors.
Non-critical items are those that contact intact skin only. These items carry minimal risk of infection if they are not handled properly. Examples of non-critical items include blood pressure cuffs, stethoscopes, and x-ray tube heads. These items must be low-level disinfected.
Sterilization and disinfection are of utmost importance. Ensure you have protocols in place for training staff prior to job duties with sterilization and disinfection. This will in turn prevent the spread of infection, keeping all safe and sound.
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