View information and guidelines surrounding sterilization, disinfection, decontamination
and ultraviolet treatment below.
Any item, device, or solution is considered to be sterile when it is completely free
of all living microorganisms, including bacterial endospores. Sterilization can be
accomplished by heat, hydrogen peroxide gas, chlorine dioxide gas, plasma, ozone,
and radiation.
Steam sterilization using an autoclave is effective as the moisture available in the
load is heated under pressure to sterilize the material. The moisture is critical
for sterilization to occur. For this reason, if a bag must be sealed prior to autoclaving,
sufficient water should be added to the bag. Flammable or other hazardous chemicals,
including bleach, should never be autoclaved without proper containment to prevent
damage to the autoclave or its pipelines. To ensure effective sterilization, the temperature
is monitored with an appropriate temperature indicator placed inside one of the bags,
and a validation is preformed to evaluate the sterilization efficiency using a spore
strip or other biological indicator.
Disinfection is generally a less lethal process than sterilization that reduces the
overall level of microbial contamination. It eliminates nearly all recognized pathogenic
microorganisms but not necessarily all microbial forms (e.g. bacterial spores) on
inanimate objects. The effectiveness of a disinfection procedure is controlled significantly
by a number of factors, each one of which may have a pronounced effect on the end
result. Among these are:
Nature and number of contaminating microorganisms including susceptibility.
Amount of organic matter present (e.g. dirt, feces, blood).
Type and condition of instruments, devices, and materials to be disinfected.
Temperature.
Contact time.
Environmental stability and shelf-life.
All chemicals are not equally effective against different types of microorganisms.
Different chemicals have different modes of action and levels of activity. It is important
to understand the mode of action to select the appropriate chemical. It is also essential
that the contact time be sufficient to allow for the action of the chemicals on the
microorganisms. Laboratorians should be sure to follow the manufacturer's instructions
for the use of all disinfectants, including preparing fresh solutions as necessary.
Decontamination renders an area, device, item, or material safe to handle (i.e. safe
in the context of being reasonably free from risk of disease transmission). The primary
objective is to reduce the level of microbial contamination so that infection transmission
is eliminated. The decontamination process may be ordinary soap and water cleaning
of an instrument, device, or area. In laboratory settings, decontamination of items,
spent laboratory materials, and regulated laboratory wastes is often accomplished
by a sterilization procedure such as steam autoclaving.
The presence of organic matter necessitates longer contact time with a decontamination
method if the item or area has not been cleaned prior. Decontamination in laboratory
settings often requires longer exposure times because pathogenic microorganisms may
be protected from contact with the decontaminating agents.
Chemical germicides used for decontamination range in activity from high-level disinfectants
(i.e. high levels of bleach), which may be used to decontaminate spills of cultured
or concentrated infectious agents in research or clinical laboratories, to low-level
disinfectants or sanitizers for general housekeeping purposes or spot decontamination
of environmental surfaces in health care settings. Resistance of selected organisms
to decontamination is presented below from least resistant to most resistant:
Lipid viruses - Least Resistant
Bacteria
Fungi
Non-lipid viruses
Mycobacteria
Bacterial spores
Prions - Most Resistant
UV light was commonly used for disinfection in pass boxes, BSCs and PCR stations.
The efficacy of UV light for disinfection is limited by a number of factors. UV light
has poor penetration, and only those microorganisms directly bathed in it will be
affected. UV lights will require regular cleaning, monitoring, and periodic replacement
to ensure germicidal activity.
Wavelengths below 280nm cause chemical reactions and therefore have germicidal action.
UV light will only be effective on exposed surfaces such as the interior of a BSC
and not on items where there is no direct contact of the UV radiation with the item
(i.e. under other items or in shadowed areas). Personnel should avoid exposure to
light in this wavelength region since brief exposure can cause erythema, harming skin
and eyes.
