Work with microorganisms in the laboratory setting may create situations whereby the normal route of transmission is circumvented. In the lab, the concentration and volume of microorganisms are typically higher than those encountered in nature, and procedures provide opportunities for infection via non-canonical routes such as splash to mucosa or needle stick. In the event of an exposure, some individuals will be at higher risk due to an immunocompromised, immunosuppressed, or susceptible immune status. Many things can reduce the immune response to opportunistic pathogens, such as very young or very old age, pregnancy, asthma, bone marrow or organ transplantation, immune deficiencies, AIDS, smoking, cancer treatment, and prolonged use of corticosteroids or certain other medications.
Based on risk assessments, the IBC has determined that Biosafety Level 2 (BSL-2) is appropriate for handling the following microorganisms:
- Adeno-associated virus (AAV): The wildtype virus is generally considered Risk Group 1 because it usually requires another virus for replication. BSL-1 laboratory precautions are acceptable for gutted AAV vectors (e.g., missing the rep and cap genes) except when higher hazard transgenes (e.g., oncogenes, toxins) are expressed or high titers or large volumes of virus are used, in which case BSL-2 is required. Animals administered AAV must be housed at Animal Biosafety Level 2 (ABSL2) and handled inside a biosafety cabinet for the first 72 hours. The first cage change must be done inside a biosafety cabinet even if more than 72 hours have elapsed. Bedding from the first cage change must be treated as biohazardous and be inactivated or disposed via an approved method (e.g., autoclaving).
- Other microorganisms not known to cause disease in humans may require BSL2 or higher containment if they are:
- An animal pathogen that would put animal colony health at risk
- An uncharacterized strain or species with unknown pathogenic potential (e.g., certain clinical or environmental isolates)
- Highly resistant to antibiotics
- Genetically modified in a manner that alters pathogenicity, virulence, transmission, or tropism
- Opportunistic pathogens designated Risk Group 2 in Appendix B of the NIH Guidelines, in BMBL, or by a public health agency such as the Center for Disease Control and Prevention (CDC) or Public Health Agency of Canada require BSL2 containment. These include but may not be limited to:
- Aspergillus flavus and A. fumigatus: May cause opportunistic infections in the immunocompromised individual.
- Bacillus anthracis (Sterne): A vaccine strain and is missing an important virulence factor. There are some reports of pathogenicity of this strain in animals. Furthermore, per guidance from CDC, BSL-2 practices will avoid contamination of the lab, which could cause problems in confounding detection of anthrax.
- Bacillus cereus: A foodborne pathogen produces toxin and causes cutaneous infections in healthy adults.
- Candida albicans: An opportunistic pathogen with significant consequences for individuals with stressed immune systems.
- Clostridum difficile: The “new” epidemic strain (B1/NAP-1) of this bacterium has substantial clinical consequences, is usually resistant to some antibiotics such as fluoroquinolones, and can infect healthy adults.
- Enterococcus faecalis and E. faecium: All vancomycin resistant strains are included. Furthermore, containment will minimize contamination of surfaces in the lab, which is important because this pathogen is extremely hardy in its ability to survive for weeks on environmental surfaces.
- Pneumocystis jiroveci (P. carinii f.sp. hominis): Causes opportunistic infections in the immunocompromised individual.
- Pseudomonas aeruginosa: Causes eye infections, especially in contact lens wearers, chronic respiratory infections among cystic fibrosis patients and may be invasive in persons taking antibiotic therapies.
- Salmonella typhimurium LT2: There is evidence that this strain may cause disease in healthy adults as well as immunocompromised individuals.
- Stenotrophomonas maltophilia: Has been implicated in infrequent ocular infections, primarily in patients with ocular compromise. Of particular concern is that treatment is limited by resistance to common antibiotics.
Employees with questions or concerns related to their health, immune, or pregnancy status are encouraged to consult with Occupational Medicine.
Most wet labs will meet the standards for a BSL-2 facility. Some of the practices utilized under BSL-2 containment are:
- Biohazard signs are posted on the door to the laboratory when work with the microorganism is in progress.
- Individuals who may be exposed are informed of the potential risks to their health posed by the pathogen.
- Exposures are treated with first aid and reported to the PI and Occupational Medicine for medical evaluation.
- The lab is under negative air pressure relative to adjacent non-laboratory spaces and the lab door is kept closed to maintain negative pressure.
- Many procedures can be conducted at the open lab bench under BSL-2 containment, but activities involving high concentrations, large volumes, or that generate aerosols need to be avoided or done in containment.
- Use of a biological safety cabinet is preferred but is not required; alternative containment equipment may be acceptable.
- Disinfectants are chosen that are effective against the pathogens handled.
- Submission of a biosafety protocol is required.