CST Sterilization & Infection Control 2 — Questions and Answers
Question 1: Which biological indicator organism is used to verify the efficacy of ethylene oxide (EO) sterilization?
- Geobacillus stearothermophilus
- Bacillus atrophaeus (Correct answer)
- Bacillus subtilis var. niger
- Clostridium sporogenes
Correct answer: Bacillus atrophaeus
Bacillus atrophaeus (formerly B. subtilis var. niger) spores are the standard biological indicator for ethylene oxide sterilization cycles.
Question 2: The term 'bioburden' refers to:
- The weight of a surgical instrument set
- The number of viable microorganisms on a device before sterilization (Correct answer)
- The concentration of disinfectant used on a surface
- The amount of organic soil remaining after decontamination
Correct answer: The number of viable microorganisms on a device before sterilization
Bioburden is the total number of viable microorganisms contaminating an item prior to sterilization.
Question 3: A sterile field is considered contaminated when:
- A scrubbed team member turns away from the field momentarily
- A sterile package is opened and placed on the field by the circulator from a distance of 12 inches
- A scrub technician reaches over the unsterile instrument table
- Moisture soaks through a sterile drape to the surface below (Correct answer)
Correct answer: Moisture soaks through a sterile drape to the surface below
Strike-through contamination occurs when moisture creates a pathway for microorganisms through a sterile drape to an unsterile surface below.
Question 4: Which sterilization method is most appropriate for heat-labile endoscopes?
- Gravity displacement steam sterilization
- Flash sterilization at 270°F
- Low-temperature hydrogen peroxide gas plasma (Correct answer)
- Dry heat sterilization
Correct answer: Low-temperature hydrogen peroxide gas plasma
Low-temperature hydrogen peroxide gas plasma (e.g., STERRAD) is used for heat-sensitive instruments like flexible endoscopes.
Question 5: The purpose of the pre-vacuum (prevacuum) phase in a dynamic-air-removal steam sterilizer is to:
- Increase the chamber pressure above atmospheric
- Remove air to allow steam penetration into porous loads (Correct answer)
- Reduce the temperature required for sterilization
- Dry the load after the sterilization cycle
Correct answer: Remove air to allow steam penetration into porous loads
The prevacuum phase evacuates air from the chamber and load so steam can penetrate porous materials uniformly.
Question 6: Standard contact time for high-level disinfection using 2% glutaraldehyde at room temperature is:
- 5 minutes
- 10 minutes
- 20 minutes (Correct answer)
- 45 minutes
Correct answer: 20 minutes
A minimum of 20 minutes at room temperature in 2% glutaraldehyde is required to achieve high-level disinfection.
Question 7: Which packaging material is NOT compatible with hydrogen peroxide gas plasma sterilization?
- Tyvek pouches
- Polypropylene wraps
- Paper/cellulose-based wraps (Correct answer)
- Nonwoven polypropylene wraps
Correct answer: Paper/cellulose-based wraps
Cellulose-based materials (paper) absorb hydrogen peroxide, interfering with the plasma cycle and are therefore incompatible.
CST Sterilization & Infection Control 2
Which biological indicator organism is used to verify the efficacy of ethylene oxide (EO) sterilization?