Primary Biosafety Levels and Agents of Disease

Biosafety level designations are based on a composite of the design features, construction, containment facilities, equipment, practices and operational procedures required for working with agents from the various risk groups.

Laboratory facilities are designated as: 

Bio-safety Level One:

  1. Facilities and Practices
    Standard, open bench, no special facilities needed; typical of most microbiology teaching labs; access may be restricted.
  2. Risk of Infection and Class of Pathogens
    Low infection hazard; microbes not generally considered pathogens and will not colonize the bodies of healthy persons; Micrococcus luteus, Bacillus megaterium, Lactobacillus, Saccharomyces.

    Classification of infective microorganisms by risk group

Bio-safety Level Two:

  1. Facilities and Practices
    At least level 1 facility and practices; plus personnel must be trained in handling pathogens; lab coats and gloves required; safety cabinets may be needed; biohazard signs posted; access restricted.
  2. Risk of Infection and Class of Pathogens
    Agents with moderate potential to infect; class 2 pathogens can cause disease in healthy people but can be contained with proper facilities; most pathogens belong to class 2; includes Staphylococcus aureus, Escherichia coli, Salmonella spp., Corynebacterium diphtheriae; pathogenic helminths; hepatitis A, B, and rabies viruses; Cryptococcus and Blastomyces.

    Table:Relation of risk groups to biosafety levels, practices and equipment

Bio-safety Level Three:

  1. Facilities and Practices
    Minimum of level 2 facilities and practices; plus all manipulation performed in safety cabinets; lab designed with special containment features (Air lock, Negative air pressure); only personnel with special clothing (Body fully covered) can enter; no unsterilized materials can leave the lab; personnel warned, monitored, and vaccinated against infection dangers.
  2. Risk of Infection and Class of Pathogens
    Agents can cause severe or lethal disease especially when inhaled; class 3 microbes include Mycobacterium tuberculosis, Francisella tularensis, Yersinia pestis, Brucella spp., Coxiella burnetii, Coccidioides immitis, and yellow fever, WEE, and HIV.

Bio safety Level Four:

  1. Facilities and Practices
    Minimum of level 3 facilities and practices; plus facilities must be isolated with very controlled access (Increased Surveillance, Entry Security  such as Proximity Key card, Retinal Scan) ; clothing changes and showers (chemical showers) required for all eligible people entering and leaving; Completely sealed doors, Rooms with Negative Pressure; materials must be autoclaved or fumigated prior to entering and leaving lab.
  2. Risk of Infection and Class of Pathogens
    Agents are highly virulent microbes that pose extreme risk for morbidity and mortality when inhaled in droplet or aerosol form; most are exotic flaviviruses; arenaviruses, including Lassa fever virus; or filoviruses, including Ebola and Marburg viruses.
Summary of biosafety level requirements

Download Laboratory Biosafety Manual – Third Edition from World Health Organization

Table Source: Laboratory Biosafety Manual published by WHO