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Biohazards – an inevitable part of scientific research.

While harmful to the health of living organisms, they can provide useful tools or be by-products of critical work. The important part is being able to remove them. Biohazardous materials can be found on equipment we used (such as CO2 incubators), work surfaces (such as those inside biosafety cabinets), containers, or even our own hands.

Many terms are used (often interchangeably) to describe the removal of biohazards. In the lab, we often say that a work surface or piece of equipment needs to be “decontaminated.” “Sterile” items need to be used. We need to “disinfect” the work area. Is there a difference in what these terms mean? What do they imply that you are supposed to do?

Decontamination is a generic term used to describe a process or treatment that makes an instrument, device or surface safe to touch. You have removed some biohazardous material. This method includes a wide variety of methods, including vaporized hydrogen peroxide, bleach, chlorine dioxide gas, phenols, and formaldehyde. It is generally accepted that an effective decontamination involves a reduction in contaminating microbes of at least 6 log-folds. That is 106 or 1,000,000 times fewer microbes. This is not definitely zero. It could be, but not necessarily. For example, if there were 250,000 bacteria on a surface, 6 log-folds less would be less than 1, so zero bacteria would remain. On the other hand, if there were 10 billion mold spores in a waterpan, 6 log-folds less would be 10,000 mold spores remaining. That is plenty to set up a new infection again.

If your goal is to achieve the destruction all forms of microbial life either physically or chemically (reducing the biological material to zero), then you would use the term sterilization. Autoclaving is an example of sterilization. This is the most absolute term when referring to the different types of decontamination. If done properly, some of the methods listed for decontamination may result in sterilization, such as vaporized hydrogen peroxide. All sterilization methods are types of decontaminations.

It is also possible to disinfect something. This is also a type of decontamination that involves chemically or physically killing microorganisms, but not spores. Spores are tiny, single-celled packages of the essential living material of microorganisms capable of giving rise to daughter cells. When conditions for life get too stressful, the microbes develop spores to survive the harsh new environment. When favorable conditions return, the spores will begin replicating to establish growth again. Sterilization will kill spores. Disinfection will not. Disinfection includes UV light treatment, bleach and alcohols. Not all disinfectants are appropriate for all microorganisms, and are dependent upon concentration and the time the disinfectant is left in contact with the surface. Resources like the Guideline for Disinfection and Sterlization in Healthcare Facilities from the CDC in 2008 can be very helpful for determining if you are using the proper reagent for your microorganism.

Lastly, there is antisepsis. This is when a liquid antimicrobial chemical is applied to living tissue. This includes handwashing with antimicrobial soap and alcohol swabbing before an injection. Since the chemical is applied directly to living tissue, it is the least potent, and least likely to result in a complete kill of all contaminating microbes.

While all of these terms apply to the same idea (reducing a biohazard contamination level), it is apparent that they are not equal, and cannot be used interchangeably. It is also important to determine what the best method for your specific protocol is. Please consult your facility’s biosafety officers or trusted sources such as the CDC’s Biosafety in Microbiological and Biomedical Laboratories (BMBL). Always conduct a risk assessment before proceeding with any protocol and wear proper personal protective equipment (PPE).

Which decontamination method is right for your CO2 incubator?

The biodecontamination protocol for Cultivo® Ultra Plus CO2 incubator was designed and tested for its ability to achieve a complete kill (not just a log-fold reduction) of a wide variety of contaminating microorganisms.

Download the test report

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