Disinfection and Sterilization: A Practical Encyclopedia
Disinfection and sterilization are essential components of infection prevention and control in healthcare. They reduce the risk of transmitting infectious agents through medical devices, instruments, equipment, and healthcare environments.
However, these processes are not interchangeable. The appropriate method depends on the item, how it will be used, the level of contamination, the material involved, and the required level of microbial inactivation. In healthcare, effective processing begins with thorough cleaning.
1. Cleaning
Cleaning is the physical removal of foreign material, organic matter, and soil from an object.
It is normally performed using:
Water
Detergent
Enzymatic products
Mechanical action
Cleaning is the first step before disinfection or sterilization. Organic and inorganic material left on instruments can interfere with the effectiveness of subsequent processing.
2. Decontamination
Decontamination is the process of making an item safe to handle or use by reducing or removing contamination.
It may involve:
Cleaning
Disinfection
Sterilization
The required process depends on the intended use of the item and the level of infection risk.
3. Disinfection
Disinfection is a process that eliminates many or all pathogenic microorganisms on inanimate objects, except bacterial spores, depending on the level of disinfection.
Disinfection can be performed using:
Chemical agents
Physical methods
The appropriate disinfectant and process depend on the intended application and the microorganisms that need to be inactivated.
4. Levels of Disinfection
Healthcare disinfection is generally divided into three levels:
Low-Level Disinfection
Used primarily for noncritical items that contact intact skin.
It inactivates many vegetative bacteria, fungi, and viruses, but does not reliably eliminate bacterial spores.
Intermediate-Level Disinfection
Provides a higher level of microbial inactivation than low-level disinfection and includes activity against Mycobacterium tuberculosis under appropriate conditions.
It does not necessarily destroy bacterial spores.
High-Level Disinfection
Used primarily for semicritical medical devices that contact mucous membranes or non-intact skin.
High-level disinfection eliminates all microorganisms except small numbers of bacterial spores when properly performed.
5. Spaulding Classification
The Spaulding classification determines the required level of processing according to the infection risk associated with a medical device.
Category | Definition | Minimum Processing |
|---|---|---|
Critical | Enters sterile tissue, the vascular system, or is used for blood passage | Sterilization |
Semicritical | Contacts mucous membranes or non-intact skin | At least high-level disinfection |
Noncritical | Contacts intact skin only | Cleaning and appropriate low-level disinfection |
This classification is a central framework for medical-device reprocessing.
6. Selecting a Disinfectant
Disinfectants are not interchangeable.
Selection should consider:
Intended use
Target microorganisms
Required level of disinfection
Concentration
Contact time
Temperature
Organic load
Material compatibility
Manufacturer instructions
Healthcare facilities should use products according to their labeling and intended application.
7. Chemical Disinfectants
Common chemical disinfectant classes used in healthcare include:
Alcohols
Chlorine compounds
Hydrogen peroxide
Peracetic acid
Glutaraldehyde
Ortho-phthalaldehyde
Iodophors
Phenolics
Quaternary ammonium compounds
Different chemical classes have different microbial activity, material-compatibility profiles, safety considerations, and applications.
Accelerated Hydrogen Peroxide (AHP)
Accelerated Hydrogen Peroxide (AHP) is a hydrogen-peroxide-based disinfectant formulation used in healthcare applications.
CDC specifically discusses accelerated hydrogen peroxide within its review of hydrogen-peroxide disinfectants. In the cited evidence, a 0.5% accelerated hydrogen peroxide formulation demonstrated bactericidal and virucidal activity in 1 minute and mycobactericidal and fungicidal activity in 5 minutes under the studied conditions.
The performance of an AHP product should not be generalized across all formulations. The appropriate concentration, contact time, intended use, microorganism claims, and material compatibility must be established from the specific product's validated claims and labeling. CDC emphasizes that commercial disinfectant formulations are unique products and should be selected and used according to their intended purpose and labeling.
AHP should therefore be understood as a disinfectant technology within the hydrogen-peroxide category, rather than as a synonym for hydrogen peroxide in general or as a sterilization claim.
8. Contact Time
Contact time is the period during which a disinfectant must remain in contact with the treated surface or device under specified conditions to achieve its labeled antimicrobial activity.
The required time depends on the product and application.
The label instructions should always be followed, including:
Concentration
Contact time
Temperature
Application method
Rinsing requirements, when applicable
A product that dries before the required exposure time may not achieve the intended efficacy.
9. Material Compatibility
A disinfection or sterilization process must be compatible with the device being processed.
Important considerations include:
Corrosion
Damage to plastics or polymers
Changes in optical properties
Damage to adhesives
Residue
Repeated exposure to chemicals
Manufacturer compatibility instructions
CDC specifically notes that chemical compatibility should be considered when selecting disinfectants for patient-care equipment.
10. Environmental Disinfection
Healthcare environmental surfaces can become contaminated and contribute to the transmission of microorganisms.
Environmental cleaning and disinfection should consider:
Frequently touched surfaces
Patient-care areas
Shared equipment
Visible contamination
Type of surface
Cleaning frequency
Appropriate disinfectant selection
Environmental cleaning and appropriate equipment disinfection are fundamental measures for reducing the potential contribution of contaminated surfaces to healthcare-associated infections.
11. Medical Device Reprocessing
Medical device reprocessing is the controlled process used to prepare reusable devices for safe subsequent use.
A basic workflow is:
Collection → Cleaning → Disinfection and/or Sterilization → Inspection → Packaging, when applicable → Storage
The required level of processing is determined primarily by the device's Spaulding classification.
12. Sterilization
Sterilization is a process that destroys or eliminates all forms of microbial life, including bacterial spores.
CDC identifies several sterilization technologies used in healthcare, including:
Steam under pressure
Dry heat
Ethylene oxide (EtO)
Hydrogen peroxide gas plasma and other validated hydrogen-peroxide-based systems
Other validated physical or chemical sterilization technologies
The method must be appropriate for the device and its materials.
13. Steam Sterilization
Steam sterilization uses saturated steam under pressure to achieve microbial destruction.
It is the preferred method for heat- and moisture-stable critical instruments because it is reliable, rapidly microbicidal, and sporicidal.
Successful steam sterilization requires appropriate control of parameters such as:
Temperature
Pressure
Exposure time
Steam contact
Air removal
The manufacturer's instructions for the instrument, sterilizer, and packaging system must be followed.
14. Low-Temperature Sterilization
Low-temperature sterilization is used for heat- or moisture-sensitive critical devices that cannot safely undergo steam sterilization.
Examples include:
Ethylene oxide
Hydrogen peroxide gas plasma and related hydrogen-peroxide systems
Other validated low-temperature technologies
The technology selected must be compatible with the device and validated for the intended application.
15. Packaging and Storage
Packaging protects sterilized items from contamination after processing.
Key principles include:
Use an appropriate packaging system.
Ensure the package remains intact.
Store processed items in a manner that maintains their sterility.
Inspect packages before use.
Do not use items with compromised packaging or indicators suggesting inadequate processing.
Sterile storage is therefore part of the overall reprocessing system, not a separate step from sterilization quality.
16. Monitoring Sterilization
Sterilization processes should be routinely monitored using a combination of:
Mechanical Monitoring
Measures physical parameters such as:
Time
Temperature
Pressure
Chemical Monitoring
Chemical indicators show that specified sterilization conditions have been reached.
However, chemical indicators do not by themselves prove that sterilization has been achieved.
Biological Monitoring
Biological indicators use highly resistant spores to directly challenge the sterilization process.
CDC identifies biological indicators as the only process indicators that directly monitor the lethality of a sterilization process.
17. Bowie-Dick Testing
For dynamic-air-removal steam sterilizers, an air-removal test, commonly known as the Bowie-Dick test, should be performed daily in an empty sterilizer.
The test evaluates effective air removal, which is essential for proper steam penetration.
18. Sterilization Failures
A sterilization process can fail because of problems such as:
Inadequate cleaning
Incorrect cycle parameters
Improper loading
Poor air removal
Inadequate sterilant penetration
Equipment malfunction
Packaging problems
Procedural errors
Monitoring systems help identify these problems and support corrective action.
19. Reprocessing Quality and Documentation
Effective reprocessing requires more than selecting a disinfectant or sterilizer.
A reliable system should include:
Standardized procedures
Manufacturer instructions
Trained personnel
Monitoring
Documentation
Equipment maintenance
Quality assurance
Corrective action when failures occur
The objective is to make the entire reprocessing pathway reliable and reproducible.
20. Common Disinfection and Sterilization Errors
Common errors include:
Skipping or inadequately performing cleaning.
Choosing the wrong level of processing.
Using an inappropriate disinfectant.
Incorrectly diluting a chemical.
Not meeting the required contact time.
Ignoring material compatibility.
Overloading sterilizers.
Using incorrect cycle parameters.
Failing to monitor sterilization.
Using an item when packaging or monitoring indicates inadequate processing.
These errors can compromise microbial inactivation and increase the risk associated with contaminated or inadequately processed healthcare equipment.