Aseptic Technique and Contamination Flashcards

Which classification of biosafety cabinet is appropriate for working with BSL-3 pathogens?

Answer: Class II Type B2 or Class III BSC

Class II Type B2 BSCs (100% exhaust) or Class III BSCs (completely enclosed glove boxes) provide the containment required for BSL-3 work.

What is the significance of the 'dead zone' at the front edge of a biosafety cabinet work surface?

Answer: Air turbulence at the cabinet opening disrupts laminar flow making this area least protected

The front edge of the BSC work surface is subject to air turbulence where room air meets cabinet airflow, disrupting sterile conditions — critical work should be performed further back in the cabinet.

When performing an autoclave validation, what biological indicator organism is typically used?

Answer: Geobacillus stearothermophilus spores

Geobacillus stearothermophilus spores are the standard biological indicator for steam autoclave validation because they are among the most heat-resistant organisms known.

A technician must transfer a sterile solution from a large bottle to a smaller container. What is the best aseptic practice?

Answer: Work inside the BSC, flame bottle neck if glass, pour without touching inside surfaces, recap immediately

Inside the BSC, careful handling prevents contamination; avoiding contact with internal surfaces and recapping immediately preserves sterility.

Which of the following is NOT a physical indicator of contamination in a mammalian cell culture?

Answer: Cells growing in a monolayer as expected

Cells growing in a normal monolayer is an expected, healthy finding — not an indicator of contamination. The other options all signal potential contamination.

What is the purpose of using a 0.22 µm membrane filter when preparing cell culture media supplements?

Answer: To sterilize the solution by removing bacteria and larger microorganisms

A 0.22 µm filter physically removes bacteria and fungi, sterilizing heat-sensitive solutions that cannot be autoclaved.