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.

Classification of microorganisms according to risk group. 

Risk GroupsRisk AssessmentExplanations
Risk Group 1 (RG1)No or low individual and community riskA microorganism that is unlikely to cause human or animal disease. E.g. S. cerevisiae (yeast), Lactobacillus, B. subtilis
Risk Group 2 (RG2)Moderate individual risk, low community riskA pathogen that can cause human or animal disease but is unlikely to be a serious hazard to laboratory workers, the community, livestock or the environment. Laboratory exposures may cause serious infection, but effective treatment and preventive measures are available and the risk of spread of infection is limited. E.g.  Streptococcus, Herpes virus, most mammalian cell lines
Risk Group 3 (RG3)High individual risk, low community riskA pathogen that usually causes serious human or animal disease but does not ordinarily spread from one infected individual to another. Effective treatment and preventive measures are available. E.g. Yersinia pestis, HIV, SARS virus
Risk Group 4 (RG4)High individual risk and community riskA pathogen that usually causes serious human or animal disease and that can be readily transmitted from one individual to another, directly or indirectly. Effective treatment and preventive measures are not usually available. E.g. Ebola virus, Marburg virus, Lassa virus

Laboratory facilities are designated as: 

  • basic – Biosafety Level 1,
  • basic – Biosafety Level 2,
  • containment – Biosafety Level 3, and
  • maximum containment – Biosafety Level 4.

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.

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; including Staphylococcus aureus, Escherichia coli, Salmonella spp., Corynebacterium diphtheriae; pathogenic helminths; hepatitis A, B, and rabies viruses; Cryptococcus and Blastomyces.

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

Risk GroupBiosafety LevelLaboratory TypeLaboratory PracticesSafety Equipment
1Basic-Biosafety Level 1Basic teaching, researchGood Microbiological Techniques (GMT)None; open benchwork
2Basic-Biosafety Level 2Primary health services; diagnostic services, researchGMT plus protective clothing, biohazard signOpen bench plus BSC for potential aerosols
3Containment-Biosafety Level 3Special diagnostic services, researchAs Level 2 plus special clothing, controlled access, directional airflowBSC and/or other primary devices for all activities
4Maximum containment- Biosafety Level 4Dangerous pathogen unitsAs Level 3 plus airlock entry, shower exit, special waste disposalClass III BSC, or positive pressure suits in conjunction with Class II BSCs, double-ended autoclave (through the wall), filtered air

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 (airlock, 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 the 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
Summary of biosafety level requirements

Reference and further reading

  1. Download Laboratory Biosafety Manual – Third Edition from World Health Organization
  2. Table Source: Laboratory Biosafety Manual published by WHO

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.

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