CTBS Sterilization Methods 5 — Questions and Answers
Question 1: What is the purpose of the 'overkill' approach in sterilization validation?
- Using twice the normal sterilant concentration
- Achieving at least 12-log reduction regardless of initial bioburden (Correct answer)
- Applying two sequential sterilization methods
- Running two biological indicator populations simultaneously
Correct answer: Achieving at least 12-log reduction regardless of initial bioburden
The overkill approach targets a 12-log reduction of highly resistant organisms, providing a large safety margin independent of measured bioburden.
Question 2: Which regulatory agency requires tissue establishments to validate their sterilization processes and maintain process records?
- CDC
- OSHA
- FDA (21 CFR Part 1271) (Correct answer)
- EPA
Correct answer: FDA (21 CFR Part 1271)
The FDA, under 21 CFR Part 1271, requires tissue establishments to validate processing steps including sterilization and maintain comprehensive records.
Question 3: A tissue bank uses supercritical CO₂ (scCO₂) for sterilization. Which advantage does this method offer over gamma irradiation?
- Lower equipment and operating costs
- Preservation of sensitive biological molecules at low temperatures (Correct answer)
- Greater penetration depth in dense tissues
- No need for post-process aeration
Correct answer: Preservation of sensitive biological molecules at low temperatures
scCO₂ operates at low temperatures and near-neutral conditions, preserving growth factors and collagen structure better than high-dose radiation.
Question 4: In radiation sterilization, what is the 'dose audit' conducted for?
- Confirming that radiation equipment was properly calibrated on the day of processing
- Verifying that each product lot received a dose within the validated minimum and maximum range (Correct answer)
- Auditing the biological indicator log reduction achieved
- Checking gamma source activity against the decay schedule
Correct answer: Verifying that each product lot received a dose within the validated minimum and maximum range
A dose audit verifies that actual radiation doses received by each production lot fall within the minimum (sterility) and maximum (tissue integrity) validated dose limits.
Question 5: What sterilization challenge is unique to prion-contaminated tissue and cannot be addressed by standard terminal sterilization methods?
- Prions are resistant to all known chemical sterilants and standard radiation doses (Correct answer)
- Prions require lower temperatures than available in standard cycles
- Prions are inactivated by ETO but not by radiation
- Prions produce toxins that survive sterilization
Correct answer: Prions are resistant to all known chemical sterilants and standard radiation doses
Prions (misfolded proteins) are extraordinarily resistant to heat, radiation, and chemical sterilants, making donor screening the primary risk mitigation strategy.
Question 6: When revalidating a sterilization process after a significant equipment change, which element is NOT required?
- Performance qualification (PQ) runs
- Updated dose-mapping or cycle studies
- Full re-IQ of unaffected auxiliary systems (Correct answer)
- Repeat biological indicator studies
Correct answer: Full re-IQ of unaffected auxiliary systems
Revalidation focuses on the changed system; components unaffected by the change do not require re-Installation Qualification (IQ) unless the change could logically affect them.
Question 7: Which sterilization method is considered MOST compatible with maintaining the viability of living cellular tissue grafts?
- Terminal gamma radiation at 25 kGy
- Ethylene oxide (ETO) terminal sterilization
- Aseptic processing without terminal sterilization (Correct answer)
- Supercritical CO₂ sterilization
Correct answer: Aseptic processing without terminal sterilization
Living cellular grafts (e.g., viable bone marrow or certain skin grafts) cannot withstand terminal sterilization and require rigorous aseptic processing to preserve cell viability.
CTBS Sterilization Methods 5
What is the purpose of the 'overkill' approach in sterilization validation?