Decontamination,Sterilization

Understanding the various cleaning levels can help you identify an appropriate safety and decontamination plan for your facility.

These days, issues of contamination control have been thrown into the daily spotlight, whether from the news reporting on a Norovirus outbreak on a cruise ship, a MRSA outbreak in the local hospital, or your fear of catching a cold from a co-worker or family member. These same issues exist in today’s laboratory, research, and production environments as well. This article will focus on the various levels of cleanliness as it applies to the laboratory area, and the appropriate methods of biological contamination control.

Cleanliness Defined
The various levels of biological cleanliness can be broken down into three categories: sanitization, disinfection, and sterilization. Sanitization and disinfection are both described as the destruction of “most”microorganisms on a surface, whether by heat or chemicals.When we take a closer look at the two, we are able to further define them quantitatively by the bio-burden reduction that each provides. The bio-burden is defined as the degree of microbial contamination or microbial load; or the number of microorganisms contaminating an object. To evaluate the bio-burden reduction, we start with a known number of spores and expose them to the agent and then evaluate if we have successfully destroyed all or some of the spores. Typically we start with a population of 4 log or 6 log (10⁴ or 10⁶) spores of a specifically known spore that is resistant to kill, such as Geobacillus Stearothermophilus or another similar spore.

Sanitization will offer a contamination reduction or bio-burden reduction of 99.9% or 3 log (10³). This means that we can expect that out of one million microorganisms, a sanitizer will destroy approximately 990,000 of the organisms leaving behind many viable microorganisms to reproduce. Sanitization is accomplished by utilizing chemicals and gels to achieve this level of cleanliness.

Disinfection will offer a bio-burden reduction of 99.99% and up to 99.999% or up to 5 log (10⁵). This means that we can expect that out of one million microorganisms, a disinfectant will destroy up to 999,990 of the organisms leaving behind very few, but still some, viable organisms. Disinfection is accomplished by utilizing many different chemicals or ultraviolet light.

Sterilization is the statistical destruction of all microorganisms and their spores. This is defined as 6 log (10⁶) or a 99.9999% reduction. Statistically, this definition is accepted as zero viable organisms surviving. Sterilization is accomplished via several methods including ionized hydrogen peroxide or other hydrogen peroxide based solutions, high heat, ultraviolet light, ozone, radiation, and chemicals (chlorine, formaldehyde, glutaraldehydes, etc.).

Now we can apply these definitions to their applications in today’s laboratory animal facilities. Here we find many types of surfaces, equipment, materials, people, and animals—all of which have contamination control challenges. You need to protect your lab workers, your animals, and, hopefully, the environment. To accomplish this, a detailed contamination control plan should be in place for all laboratory facilities.

Methods of Providing the Appropriate Level of Cleanliness

Sanitization
Sanitization can be accomplished in a very easy and inexpensive manner. We’ve all been trained from the time we were small children to wash our hands before eating. Washing your hands often will help protect you from germs. The Centers for Disease Control and Prevention (CDC) recommends that when you wash your hands with soap and warm water, that you wash for at least 15 to 20 seconds.When soap and water are not available, alcohol-based disposable hand wipes or gel sanitizers may be used. If using gel, rub your hands until the gel is dry. The gel does not need water to work. The alcohol in it kills the germs on your hands. Washing your hands before entering or leaving a laboratory should be a key component of any contamination control plan. By doing this, you will protect both your work from any germs that may have been on your hands prior to entering the laboratory, as well as protecting you from taking any of the germs outside of the laboratory. Hand sanitizing should be done each and every time you enter or leave the laboratory or any other critical area.

Disinfection and Sterilization
Decontamination is any activity that reduces the microbial contamination of materials or surfaces to prevent inadvertent infection. The appropriateness of a decontamination procedure depends on your goal.Do you wish to disinfect or sterilize?Will you be using the disinfectant on hard surfaces, in a biosafety cabinet, on instruments, or waste? Disinfection results in destruction of specific pathogenic microorganisms and refers to the elimination of virtually all pathogenic organisms on inanimate objects and surfaces thereby reducing the level of microbial contamination to an acceptably safe level.When choosing a disinfectant, one should consider the organism, the item to be disinfected, and the cost and ease of use of the disinfectant. Disinfection should be performed on all work surfaces and high touch areas including benches, countertops, bench top equipment, door and cabinet knobs, work surfaces in biosafety cabinets, incubators, etc., and will provide a higher level of cleanliness than sanitization.