Laboratory Bio-safety Levels

  • There are various types of microorganisms that are to be dealt in laboratory.
  • Their potentiality to cause or infect the laboratories workers may differ from one another.
  • The level of containment used to prevent accidental infections or accidental environmental contamination in clinical, research and teaching laboratories must be adjusted.
  • It is done to counter the bio-hazard potential of the organism handled in the laboratory.
  • Laboratories may be of different levels but on the basis of containment potential or bio-safety levels, they are categorized as BL1, BL2, BL3 and BL4.
  • Good laboratories practices must be followed by the personnel working in the laboratories at all bio-safety levels.
  • It ensures basic cleanliness and limit contamination as well as decontamination of the laboratory surfaces after each work or whenever spills occur.
  • No food or drink should be consumed and one must wash their hands before leaving the laboratory.
  • Access to laboratory is to be restricted to the laboratory personnel at all times.


A)Bio-safety level 1 (BL1)

  • These are the lowest level of containment.
  • Work can be done on the open bench with organisms that present low risk of infections.
  • These types of organisms are not pathogens in normal individuals and include organisms such as Bacillus subtilis.
  • Microbiology teaching laboratory is one of the examples of BL1 as it does not use any pathogens.


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B)Bio-safety level 2 (BL2)

  • These are designed for those organisms that present a moderate risk of infection.
  • Risk may be due to accidental ingestion, per-cutaneous injection or exposure to mucous membranes via aerosols.
  • E. coli and Streptococcous pyogenes are dealt in a BL2 laboratory or sometimes at higher containment levels.
  • Normal procedures may be done on bench tops, but barrier protection devices are used if necessary such as face and eye protection, gloves, lab coats or gowns, etc.
  • Most microbiology research, clinical and instructional laboratories falls under this category.


C)Bio-safety level 3 (BL3)

  • Pathogens having a very high potential for causing infections especially from aerosols, require this type of laboratories.
  • Mycobacterium tuberculosis, the causative agent of tuberculosis that is extremely infectious air-borne pathogens if is to be handled by the laboratory personnel, the laboratory should have special features.
  • Laboratory having negatively pressurized rooms and air filters that prevents the accidental release of the pathogen is preferred.
  • Work must not be done on the open bench for which biological safety cabinets are required.
  • In some cases, some organisms that can normally be handled in BL2 must be handled in BL3.
  • Staphylococcus aureus can be handled on culture plates normally in BL2.
  • But, when large quantities are grown and are to be centrifuged, work must be done in BL3 facility to contain potential infectious aerosols.
  • Specialized research and teaching facilities fall under this category.


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D)Bio-safety level 4 (BL4)

  • These are designed in order to handle life threatening pathogens that have high possibility of transmission by aerosols.
  • For these pathogens, there may not be effective immunization, treatment or cure.
  • There should be provision of total isolation of the organisms such as manipulation through gloves in a sealed biological safety cabinet or by personnel wearing full body, positive pressure suits with air supplies.
  • Work related to hemorrhagic fever viruses (Lassa, Marburg, Ebola), variola virus, drug-resistant M tuberculosis is done in this laboratory.
  • These laboratories are specially designed and equipped to handle the most dangerous and high risk group pathogens.
  • They are usually associated with government facilities such as Centers for Disease Control and Prevention or University laboratories that specialize in infectious disease.





Laboratory Bio-safety Levels