Approach to Disinfection and Sterilization

In the world you and I lived in, we have to accept that microorganisms are everywhere. Regardless of harmful or not, we are cautious dealing with patients and instruments. In a paper published by Professor Earle H. Spaulding from Temple University School of Medicine contrived a rational approach to disinfection and sterilization of medical instruments as well as patient-care items. As this was an unprecedented approach in the medical society, this approach provided an essence of future medical health care personnels in order to prevent major risks like introduction of infectious pathogens across patients, breach of host barriers, and transmission of environmental pathogens.


Cleaning, described by Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008 a process that remove visible soil (e.g. organic and inorganic material) from objects and surfaces and normally is accomplished manually or mechanically using water with detergents or enzymatic products.

Disinfection describes a process that eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects.

Sterilization describes a process that destroys or eliminates all forms of microbial life and is carried out in healthcare facilities by physical or chemical methods.

Germicide is an agent that can kill microorganism, particularly killing pathogenic organisms; germicide includes both antiseptics and disinfectants.

Antiseptic is germicide applied to living tissue and skin.

Disinfectant is germicide applied only to inanimate objects.

Spaulding Classification:

Critical items are items that have a high risk for infection if they are contaminated with any microorganism and must keep sterile at all time. Items include surgical instruments, cardiac and urinary catheters, implants, and ultrasound probes used in sterile body cavities.

Semicritical items are items that contact mucous membranes or non intact skin and should be free from all microorganisms; however small numbers of bacterial spores are permissible. Items include respiratory therapy and anaesthesia equipments, some endoscopes, laryngoscope blades, oesophageal manometry probes, cystoscopes, anorectal manometry catheters, and diaphragm fitting rings.

Noncritical items are items that come in contact with intact skin but not mucous membranes. Noncritical items are categorized into noncritical patient care items and noncritical environmental surfaces. Noncritical patient care items include bedpans, blood pressure cuffs, crutches and computers; these items can be decontaminated before reuse. Noncritical environmental surfaces are frequently touched by hand; include bed rails, some food utensils, bedside tables, patient furniture and floors. Noncritical items can potentially contribute to secondary transmission by contaminating hands of health-care workers or by contacting medical equipment that subsequently contacts patients.

In dentistry, increased publicity about potential transmission of infectious agents focused attention on dental instruments as possible pathogen transmission agents. The American Dental Association recommends surgical and other instruments that normally penetrate soft tissue or bone be classified as critical devices that should be sterilised after each use or discarded. Instruments not intended to penetrate oral soft tissues or bone but that could contact oral tissue are classified as semicritical devices, however sterilization after each use is recommended if the instruments are heat-tolerant. If the instrument is heat-sensitive, it should be at least processed with high-level disinfectant. Common methods of sterilization for both heat-stable critical and heat-stable semicritical dental instruments are autoclave, chemical capo, and dry heat.


Common sterilization method in dentistry – autoclave


Noncritical surfaces are divided into clinical contact surfaces and housekeeping surfaces; clinical contact surfaces that are frequently touched with gloved hands during patient are or contaminated with blood or other potentially infectious material and subsequently contact instruments, hands, gloves, or devices. Barrier protective coverings are recommended for clinical contact surfaces and should be changed when visibly soiled or damaged and routinely. Protected surfaces should be disinfected as well at the end of each day or if contamination is evident. If not barrier-protected, these surfaces should be disinfected between patients with an intermediate disinfectant or low-level disinfectant.

Housekeeping surfaces need to be cleaned only with a detergent and water or hospital disinfectant depending on nature of the surface and degree of contamination.


Surface Disinfection Example


Mail-return sterilization monitoring services use to test sterilizers in dental clinics with spore strips are recommended, but can create false-negative results from delayed mailing to laboratory.

Reduced susceptibility to disinfectants of microbes does not correlate with failure of the disinfectant since the concentration used in disinfection still greatly exceed the bactericidal level. For example, gentamicin resistance in some S. aureus strains have shown reduced susceptibility to propamidine, quaternary ammonium compounds, and ethidium bromide. However, clinical relevance of these observations is questionable as the concentration of disinfectants used in practice are much higher than the minimum inhibitory concentration. The rotational use of disinfectants in some environments has been recommended and practiced to prevent development of resistant microbes.

Surfaces are considered noncritical items because they contact intact skin. However, medical equipment surfaces as well as environment surfaces could potentially contribute to cross-transmission by contamination of health-care personnel from hand contact with contaminated surfaces, medical equipments or patients. There are several reasons that surface disinfection with germicidal detergent is recommended. First, hospital floors become contaminated with microorganisms from settling airborne bacteria: by contact with shoes, wheels, and other objects; and occasionally by spills. Bacterial counts pretreatment level and post treatment level are similar with only soap and water after a few hours; studies shown that soap and water (80% reduction) was less effective in reducing the numbers of bacteria than was a phenolic disinfectant (94-99.9%). Second, detergents become contaminated and result in seeding the patient’s environment with bacteria as investigators have shown that mop water becomes increasingly dirty during cleaning and becomes contaminated if soap and water is used rather than a disinfectant. Third, the CDC Isolation Guideline recommends that noncritical equipment contaminated with blood, body fluids, secretions, or excretions be cleaned and disinfected after use; in addition to cleaning, disinfection of the bedside equipment and environmental surfaces is indicated for certain pathogens that can survive in the inanimate environment for prolonged periods. Fourth, OSHA requires that surfaces contaminated with blood and other potentially infectious materials be disinfected. Fifth, using a single product throughout the facility can simplify training and appropriate practice.

As for this guideline, it provides health-care personnels a foundation to follow; furthermore, health-care personnels could and should expand on this guideline to provide a safer environment.

A video is added to enhance your understanding!

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