Decontamination is the process of making an object or surface safe for handling, use, or disposal by reducing the number of microorganisms present to an acceptable level. This process is a spectrum of procedures tailored to the item’s intended use and the potential risk of infection. The highest levels of decontamination are reserved for items that will have direct contact with the most sensitive areas of the human body.
Establishing the Hierarchy: Cleaning and Disinfection
The decontamination process begins with cleaning, which is the physical removal of visible soil, organic matter, and foreign material from a surface. This step is foundational because organic debris can shield microorganisms from subsequent chemical or heat treatments, making them less effective. Cleaning alone does not kill microbes but significantly reduces the overall microbial load, preparing the item for the next stage.
Following cleaning is disinfection, which involves the destruction of pathogenic microorganisms, though not necessarily all microbial forms. Disinfection is categorized into three levels: low-level, intermediate-level, and High-Level Disinfection (HLD). HLD eliminates all microorganisms, including bacteria, fungi, and viruses, but cannot reliably eliminate large numbers of highly resistant bacterial spores.
Items that contact mucous membranes or non-intact skin, such as flexible endoscopes, typically require HLD. The inability of HLD to guarantee the destruction of bacterial spores is the reason it is considered insufficient for the highest standard of decontamination.
Defining the Highest Level: Sterilization
The highest level of decontamination is sterilization, which is defined as the complete elimination or destruction of all forms of microbial life. This process targets the most resilient organisms, including bacterial spores, which are dormant, highly protected structures formed by certain bacteria, like Clostridium difficile. The successful destruction of these spores is the defining feature that separates sterilization from High-Level Disinfection.
Sterilization effectiveness is measured using the Sterility Assurance Level (SAL), a concept rooted in probability, rather than a simple binary outcome. The standard for a product to be labeled “sterile” is typically an SAL of \(10^{-6}\). This means there is a one-in-a-million chance that a single viable microorganism remains on the item after the process is complete.
This stringent standard is mandated for all items classified as “critical” under the Spaulding Classification system. Critical items are those that enter sterile tissue, the vascular system, or any body cavity that is normally sterile, such as surgical instruments, implants, and cardiac catheters. Achieving this calculated probability of sterility is essential for patient safety in high-risk medical procedures.
Achieving the Highest Standard of Cleanliness
Achieving the required Sterility Assurance Level necessitates the use of validated physical or chemical processes that can penetrate materials and destroy spores. Moist heat sterilization, commonly performed using an autoclave, is the most common and reliable method. This process utilizes pressurized steam at \(121^\circ\text{C}\) to \(134^\circ\text{C}\) for a specific duration, causing irreversible coagulation of microbial proteins.
For materials that cannot withstand the high temperatures of steam, alternative methods are employed. Dry heat sterilization is suitable for items like powders, oils, and glassware, which are impenetrable to moist heat. This method requires higher temperatures and longer exposure times, such as \(170^\circ\text{C}\) for 60 minutes, with the primary lethal process being the oxidation of cell components.
Chemical sterilization provides a low-temperature option for heat-sensitive instruments, such as complex surgical scopes. Effective chemical sterilants include Ethylene Oxide (EtO) gas, which interferes with microbial cell metabolism, and hydrogen peroxide plasma/vapor, which utilizes free radicals.
Radiation sterilization, primarily using gamma rays or electron beams, is often used for commercially produced, disposable medical products like pre-packaged syringes or gloves. The radiation disrupts the DNA of microorganisms, preventing them from reproducing. Regardless of the method used, the highest standard of cleanliness is only confirmed by achieving the \(10^{-6}\) Sterility Assurance Level.