Define BSL-1 and BSL-2 with examples of agents.

• A. BSL-1 is minimal risk (e.g., non-pathogenic Escherichia coli K-12); BSL-2 is moderate risk (e.g., Staphylococcus aureus); Each includes standard precautions.
• B. BSL-1 is high risk; BSL-2 is minimal risk; No precautions required.
• C. BSL-1 is for plant pathogens; BSL-2 is for animal pathogens; No standard precautions.
• D. BSL-1 and BSL-2 are identical in risk and precautions.

Answer: (A)

Biosafety levels reflect how much containment and protection are needed based on how risky an organism is. At the lowest level, work with minimal-risk, non-pathogenic organisms uses basic practices and standard hygiene. A classic example is non-pathogenic E. coli K-12. The next level involves moderate-risk organisms that can cause disease in healthy people, so additional safeguards are put in place—like wearing gloves, a lab coat, and eye protection, restricting access to the lab, and using techniques to avoid creating aerosols (often including a biosafety cabinet for certain procedures). An example is Staphylococcus aureus. Both levels rely on standard precautions as a baseline, with the higher level adding more protections. The other statements mix up risk levels, misidentify what counts as plant versus animal pathogens, or claim no precautions are needed, which don’t fit how biosafety levels are actually defined.