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Biosafety in Microbiologic and Biomedical Laboratories

The University of Texas at Tyler

IACUC Education and Training*Note: Content not specific to UT Tyler is from the American Association for Laboratory Animal Science (AALAS)

Principles of BioSafety

This lesson will define and present information on methods used to provide biosafety in facilities where potentially infectious agents are used.

These include: Containment Biological safety cabinets Personal protection equipment The facility as barrier Secondary barriers


Containment

The term containment describes safe methods for managing infectious materials in the laboratory environment where they are being handled or maintained.

The purpose of containment is to reduce or eliminate exposure to potentially hazardous agents.

Exposure could involve not only laboratory workers but other individuals working close by and the outside environment.


The three elements of containment include:

laboratory practice and technique safety equipment facility design

The risk assessment of the work to be done with a specific agent will determine the appropriate combination of these elements.

Principles of BioSafety: Primary Containment Primary containment is the protection of personnel and the immediate

laboratory environment from exposure to infectious agents.

Primary containment is provided by both good microbiological technique and the use of appropriate safety equipment.

For example, the use of vaccines may provide an increased level of personal protection. Personal protective equipment such as gowns, masks, and gloves and biological safety cabinets offer protection when used properly in conjunction with good laboratory techniques.

Sharps are a frequent cause of exposure to personnel. View some recommendations on working with sharps on the AALAS Learning Library site.

Principles of BioSafety: Secondary Containment

Secondary containment is the protection of the environment external to the laboratory from exposure to infectious materials.

Secondary containment is provided by a combination of facility design and operational practices. Ventilation systems, controlled access, airlocks, and other facility design features must be part of any biosafety program.

Principles of BioSafety: Biological Safety Cabinets Safety equipment includes biological safety

cabinets (BSCs), enclosed containers, and other engineering controls designed to remove or minimize exposures to hazardous biological materials.

The biological safety cabinet (BSC) is the principal device used to provide containment of infectious splashes or aerosols generated by many procedures

Principles of BioSafety: Biological Safety Cabinets There are three types of

biological safety cabinets used in microbiological and biomedical laboratories - Class I, Class II, and Class III.

Open-fronted Class I and Class II biological safety cabinets are primary barriers which offer significant levels of protection to laboratory personnel and to the environment when used with good laboratory techniques.

Principles of BioSafety: Biological Safety Cabinets The Class II biological safety cabinet also

provides product protection from external contamination of the materials (e.g., cell cultures, microbiological stocks) being manipulated inside the cabinet.

The gas-tight Class III biological safety cabinet provides the highest attainable level of protection to personnel and the environment.

Principles of Biosafety: Personal Protection

Safety equipment also includes items for personal protection, such as gloves, coats, gowns, shoe covers, boots, respirators, face shields, safety glasses, or goggles

Principles of Biosafety: Personal Protection

Personal protective equipment (PPE) is often used in combination with biological safety cabinets and other devices that contain the agents, animals, or materials being handled. It may be difficult or impractical to work in biological safety cabinets in some situations; in this instance, personal protective equipment may form the primary barrier between personnel and the infectious materials.

Principles of Biosafety: The Facility as a Barrier

Facility design and construction contribute to the laboratory workers' protection, provide a barrier to protect persons outside the laboratory, and protect people and animals in the community from infectious agents which may be accidentally released from the laboratory.

Principles of Biosafety: The Facility as a Barrier Laboratory management is responsible for

providing facilities that are commensurate with the laboratory's function and with the recommended biosafety level for the agents being manipulated.

A variety of experts should be part of the design team for any new facility. These include biosafety professionals, HVAC engineers and animal care professionals.

Principles of BioSafety: Biological Safety Cabinets The Biosafety in Microbiological and Biomedical

Laboratories (BMBL) 4th Edition has additional details about biosafety cabinets.

Biological safety cabinets should be performance-tested at least annually to validate proper function. It is optimal to have such testing done by an NSF-Accredited Biosafety Cabinet Field Certifier. More information is available in the CDC/NIH publication Primary Containment for Biohazards: Selection, Installation and Use of Biological Safety Cabinets, 2nd Edition.

Principles of Biosafety: Secondary Barriers The recommended secondary barrier(s)

will depend on the risk of transmission of specific agents.

When the risk of infection by exposure to an infectious aerosol is present, higher levels of primary containment and multiple secondary barriers may become necessary to prevent infectious agents from escaping into the environment

Principles of Biosafety: Secondary Barriers

Such design features include:

Specialized ventilation systems to ensure directional air flow

Air treatment systems to decontaminate or remove agents from exhaust air

Controlled access zones Airlocks as laboratory

entrances (as shown in this image)

Separate buildings or modules to isolate the laboratory

Principles of Biosafety: BioSafety Levels

Biosafety Level 1 BSL-1 laboratories are used to study

agents not known to consistently cause disease in healthy adults.

They follow basic safety procedures and require no special equipment or design features.

Principles of Biosafety: BioSafety Levels Biosafety Level 2

BSL-2 laboratories are used to study moderate-risk agents that pose a danger if accidentally inhaled, swallowed or exposed to the skin.

Safety measures include limited access, biohazard warning signs, sharps precautions, class I or II BSCs, the use of PPE such as gloves and eyewear as well as handwashing sinks and waste decontamination facilities such as an autoclave.


BSL-3 laboratories are used to study agents that can be transmitted through the air and may cause potentially lethal infection.

Researchers perform lab manipulations in class I or II BSCs or other enclosure. Other safety features include clothing decontamination, sealed windows, double-door access, and specialized ventilation systems.


BSL-4 laboratories are used to study agents that pose a high risk of life-threatening disease, aerosol-transmitted lab infections, or related agents whose risk is not known. Lab personnel are required to to shower when exiting the facility. The labs incorporate all BSL 3 features and occupy safe, isolated zones within a larger building or a separate building. Procedures are performed in Class III BSCs or Class II while wearing a positive pressure full-body suit.

The laboratory director is specifically and primarily responsible for assessing the risks and appropriately applying the recommended biosafety levels.

Risk Assessment and Recommendations:

Acquiring a Laboratory-Associated Infection

There are risks for acquiring a laboratory-associated infection from job-related activities involving infectious or potentially infectious material. Assessing risks and identifying risk management tools are critical for assigning the appropriate biosafety level to an infectious organism and reducing the worker's and the environment's risk of exposure to the absolute minimum.

Risk Assessment

Assessing the risk for acquiring a laboratory associated infection is affected by the following factors:

Pathogenicity Route of Transmission Agent Stability Infectious Dose Susceptibilty Concentration and Volume Origin

Risk Assessment

Pathogenicity The greater the pathogenicity of the infectious or suspected

infectious agent, the more severe is the potentially acquired disease, and so the higher is the risk.

For example: Since Staphylococcus aureus rarely causes a severe or life-

threatening disease in a laboratory situation, it is assigned to BSL-2.

Ebola, Marburg, and Lassa fever viruses cause diseases with high mortality rates and have no vaccines or treatment, so BSL-4 is the appropriate level to work with those viruse.

Work with human HIV and hepatitis B virus is done at BSL-2 because they are not transmitted by the aerosol route, even though potentially lethal disease can result from exposure. For hepatitis B, there is also an effective vaccine available.

Risk Assessment

Route of Transmission Agents transmitted by the aerosol route

have caused the most laboratory infections, versus agents transmitted parenterally or by ingestion. When planning work with an unknown agent with an uncertain mode of transmission, the potential for aerosol transmission must be considered due to the higher risk.

Risk Assessment

Agent Stability Desiccation, exposure to sunlight or

ultraviolet light, exposure to chemical disinfectants and other factors can affect the agent's stability in the environment.

Risk Assessment

Infectious Dose Infectious dose can vary from one to

hundreds of thousands of units.

Risk Assessment

Susceptibilty The infectious dose is affected by the individual's

resistance, so a laboratory worker's immune status is directly related to his/her susceptibility to disease when working with an infectious agent. Thus, susceptibility may be greater than in a healthy person for persons who are pregnant, have undergone surgery, are receiving immune-suppressent medications (including steroids), or who have systemic infectious diseases.

Risk Assessment

Concentration and Volume The concentration is the number of

infectious organisms per unit volume. Higher concentrations increase the risks of working with that agent. Working with large volumes of concentrated infectious material also increases the risks, since additional handling of the materials is often required.

Risk Assessment

Origin Origin may refer to geographic location

(e.g., domestic or foreign); host (e.g., infected or uninfected human or animal); or nature of source (potential zoonotic or associated with a disease outbreak).