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Decontamination for Laboratory Biosafety

Decontamination for Laboratory Biosafety



Decontamination of laboratory space is essential to prevent accumulation and spreading of microbes that can lead to the transmission of diseases.

Decontamination falls into two categories: disinfection and sterilization. Disinfection involves eliminating nearly all pathogenic microorganisms, with the exception of microbial spores on laboratory surfaces and equipment. Sterilization, on the other hand, is a more lethal process, eliminating all microbial life.

Decontamination is carried out using a variety of methods, such as chemicals, heat, or radiation. The choice of method depends on the degree of contamination as well as the type and concentration of the contaminant.

This video will illustrate the types of decontamination and the procedures for disinfection and sterilization of machines, surfaces, and equipment.

Prior to establishing a decontamination procedure, the type, concentration, and location of the microorganism must be determined. Types of microorganisms include Gram-positive or -negative bacteria; viruses; fungi; bacterial spores; and algae. Once the type of microorganism is established, a suitable disinfectant should be chosen.

When selecting a decontamination method the effectiveness of a disinfectant has to be considered, which is dependent on factors such as its chemical composition; the amount, concentration, contact time; and temperature.

Now that we have discussed how to choose a method for decontamination, let's explore the various types used for an actual procedure.

Liquid chemicals are categorized in three levels, as low-, intermediate-, and high-degree disinfectants. Regardless of which you choose, always wear appropriate personal protective equipment when working with hazardous materials.

Most non-critical microorganisms require only low-level disinfectants, which are low in toxicity, but cause irritation upon long exposure times. Common low-level disinfectants are quaternary ammonium compounds, such as benzalkonium chloride and ammonium chloride, and phenolic compounds, such as o-phenylphenol and chloroxylenol.

For the decontamination of more resistant microorganisms, alcohol-based chemicals are used in areas ranging from healthcare to laboratories.

Additionally, halogen-based compounds, such as hypochlorites and iodophors are often applied as antiseptics and disinfectants of medical equipment. However these agents have prolonged contact times and their effectiveness is decreased in the presence of organic matter.

High level disinfectants, which can be classified as oxidizers, acids, and aldehydes are used if decontamination of all microorganisms is required.

Oxidizers such as hydrogen peroxide are fast-acting and often used as antiseptics for wound cleaning and to disinfect environmental surfaces like benchtops. But be careful, as exposure to high concentrations of hydrogen peroxide can be harmful to tissue and airways.

Peracetic acid is generally used to disinfect automated machines and to sterilize medical, surgical, and dental instruments. The advantage of peracetic acid and other oxidizers is a short contact time; however, the use of material to be disinfected can be limited, due to corrosion of metals in acids, for example.

Aldehydes on the other hand, such as formaldehyde or gluteraldehyde, are non-corrosive, but are still hazardous. These chemicals are used to sterilize various types of equipment, but suffer from prolonged contact time.

In addition to liquid chemicals, gaseous chemicals may also be used for decontamination purposes. Gases such as chlorine dioxide and ethylene oxide, as well as vaporized hydrogen peroxide and peracetic acid are frequently used to rid closed equipment, such as biosafety cabinets, of bacteria, viruses, and spores.

In addition to chemicals, heat is a common physical agent for the decontamination of pathogens.

There are two forms of heat. "Dry" heat is used under conditions of 160 to 170 degrees Celsius for 2 to 4 hours to disinfect glassware, but it is not suitable for heat-labile materials. On the other hand, "Wet" heat, also known as autoclaving, is used by heating samples and equipment to only 120 degrees Celsius for 30 to 60 minutes under high pressure.

Besides heat, ultraviolet radiation in the wavelength range of 250 to 270 nanometers is often used for decontamination. This method is effective against bacteria and viruses, but not against spores, and is used to decontaminate air, water, and surfaces such as in biological safety cabinets. Furthermore UV light in this range can cause burns of skin and eyes, thus proper PPE should be worn.

You've just watched JoVE's introduction to Decontamination for Laboratory Safety. You should now understand the various types of microbial contaminants, how to choose a suitable method, and the types of disinfection and sterilization available. Thanks for watching!

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