CTBS Sterilization Methods 3 — Questions and Answers
Question 1: Which ISO standard specifically governs the development and validation of sterilization processes for medical devices and tissues?
- ISO 9001
- ISO 13485
- ISO 11135 / ISO 11137 (Correct answer)
- ISO 14971
Correct answer: ISO 11135 / ISO 11137
ISO 11135 covers ETO sterilization and ISO 11137 covers radiation sterilization validation for medical devices and tissue products.
Question 2: A tissue bank is validating a new VHP (vaporized hydrogen peroxide) sterilization cycle. Which BI organism is most appropriate?
- Bacillus atrophaeus
- Geobacillus stearothermophilus (Correct answer)
- Clostridium sporogenes
- Staphylococcus aureus
Correct answer: Geobacillus stearothermophilus
G. stearothermophilus is also used as the BI for VHP sterilization validation due to its high resistance to oxidizing agents.
Question 3: When processing cortical bone with low-dose radiation, what adjunct method is often combined to achieve adequate sterility?
- Addition of ethanol
- Aseptic processing techniques (Correct answer)
- Hyperbaric oxygen exposure
- Freeze-drying after radiation
Correct answer: Aseptic processing techniques
Low-dose radiation is often combined with rigorous aseptic processing to achieve the required SAL while minimizing tissue damage.
Question 4: The D-value in sterilization science refers to:
- The dose required to eliminate all organisms in a load
- The time or dose required to reduce the microbial population by 90% (1 log) (Correct answer)
- The maximum allowable bioburden before processing
- The distance from the radiation source to the product
Correct answer: The time or dose required to reduce the microbial population by 90% (1 log)
The D-value (decimal reduction value) is the time or dose needed to reduce the viable microbial population by one log (90%).
Question 5: Which property of ethylene oxide makes it effective as a sterilant at low temperatures?
- It is a strong oxidizer that reacts with DNA bases
- It alkylates proteins and nucleic acids, disrupting cellular function (Correct answer)
- It denatures proteins via hydrolysis
- It disrupts osmotic balance through membrane lysis
Correct answer: It alkylates proteins and nucleic acids, disrupting cellular function
ETO is an alkylating agent that chemically modifies proteins and nucleic acids, rendering microorganisms non-viable without requiring high heat.
Question 6: A tissue bank receives a BI result showing growth after a terminal sterilization run. The correct first action is:
- Release the lot with a quarantine flag
- Quarantine the lot and investigate immediately (Correct answer)
- Re-sterilize the entire lot
- Discard all products from that run
Correct answer: Quarantine the lot and investigate immediately
A positive BI indicates a potential sterilization failure; the lot must be quarantined and a root-cause investigation initiated before any disposition decision.
Question 7: What is the primary reason terminal sterilization is preferred over aseptic processing for allografts when feasible?
- It is less expensive than cleanroom processing
- It provides a validated and measurable SAL guarantee (Correct answer)
- It preserves tissue viability better
- It eliminates the need for bioburden testing
Correct answer: It provides a validated and measurable SAL guarantee
Terminal sterilization provides a mathematically defined and validated SAL, offering a higher and more reliable sterility assurance than aseptic technique alone.
CTBS Sterilization Methods 3
Which ISO standard specifically governs the development and validation of sterilization processes for medical devices and tissues?