What Are High-Level Disinfectants and Their Uses?

Disinfectants are chemicals designed to destroy or inactivate harmful microorganisms on non-living surfaces, playing an important role in preventing the spread of germs. These substances are distinct from general cleaning products, which primarily remove visible dirt and organic material. Disinfectants work by disrupting the cellular structures or metabolic processes of pathogens, thereby reducing the risk of illness transmission. Understanding the varying levels of disinfectant efficacy is important for maintaining public health and safety.

Disinfection Spectrum

Germ-killing processes range from basic cleaning to full sterilization. Cleaning involves the physical removal of dirt and some germs, typically with soap and water. Disinfection uses chemicals to kill germs on surfaces, significantly lowering the risk of infection.

Within disinfection, different levels exist based on the types of microorganisms they can inactivate. Low-level disinfectants kill most vegetative bacteria, some viruses, and fungi but are not effective against mycobacteria or bacterial spores. Intermediate-level disinfectants are more potent, capable of killing mycobacteria, most viruses, and fungi, in addition to vegetative bacteria, but may not eliminate bacterial spores. High-level disinfection (HLD) represents the most rigorous form of disinfection, targeting all microorganisms except for a high number of bacterial spores. Sterilization, the highest level of microbial control, eliminates all forms of microbial life, including bacterial spores, often through methods like heat, radiation, or specialized chemicals.

Defining High-Level Disinfectants

High-level disinfectants are chemical agents that effectively eliminate a broad range of microorganisms, including all vegetative bacteria, mycobacteria, fungi, and viruses. They do not consistently kill large numbers of bacterial spores. Their potent action makes them suitable for reprocessing medical devices that come into contact with mucous membranes or non-intact skin.

Common chemical examples include glutaraldehyde, ortho-phthalaldehyde (OPA), hydrogen peroxide, and peracetic acid. Glutaraldehyde, a dialdehyde, has been used for over 50 years and is effective against a wide range of microorganisms. OPA, another dialdehyde, gained popularity as an alternative to glutaraldehyde, offering effective antimicrobial activity. Hydrogen peroxide, often used in higher concentrations, is also a powerful high-level disinfectant. Peracetic acid, an organic acid, is known for its broad-spectrum activity, including effectiveness against bacterial spores and biofilms.

Common Applications

High-level disinfectants are primarily used in healthcare settings for reprocessing semi-critical medical devices. Semi-critical devices are those that come into contact with mucous membranes or non-intact skin but do not penetrate sterile tissues or the vascular system. Examples include flexible endoscopes, respiratory therapy equipment, and anesthesia equipment.

The use of HLD for these devices is important in preventing healthcare-associated infections (HAIs). While sterilization is preferred for critical devices that enter sterile body areas, HLD is an acceptable and often necessary method for heat-sensitive semi-critical items that cannot withstand traditional sterilization processes.

Ensuring Safe and Effective Use

Effective high-level disinfection requires specific protocols, beginning with thorough pre-cleaning of instruments. Organic matter, such as blood or tissue, can interfere with the disinfectant’s effectiveness, as this cleaning step is crucial. After cleaning, devices must be properly rinsed before disinfection.

Key considerations for effective disinfection include using the correct dilution, ensuring appropriate contact time, and maintaining the recommended temperature. For instance, some OPA solutions require 12 minutes at 20°C, while certain hydrogen peroxide and peracetic acid combinations may need 15 minutes. Regular testing of the disinfectant solution is also necessary to ensure its minimum effective concentration (MEC) is maintained.

Safety measures are important for personnel handling high-level disinfectants due to their chemical nature. Personal protective equipment (PPE), such as gloves, eye protection, and appropriate attire, should be worn to prevent skin and eye contact. Adequate ventilation helps to minimize exposure to chemical vapors. Proper storage and disposal practices, including neutralization for some disinfectants like OPA before discarding, are important for environmental and personnel safety.