Methods
1. Bioburden Method: Lethality Confirmation
- ? Direct Count/Enumeration Method
- ? Fraction-Negative Method
2. Overkill Method: Demonstrating ?12-Log Reduction
- ? Half-Cycle Method
- ? Cycle Development Method
Key Terms
- Bioburden
- 12-log reduction
- D-value
Methods Overview
1. Half-Cycle Method (Basic Principle – Run Count)
- Theoretical initial bioburden: 10?
- Test Criteria:
- 1 run with survivors allowed (“partial cycle” or “short cycle”)
- 3 half-cycles with zero survivors required
2. Cycle Calculation Method
- Requires known initial bioburden & lethality rate
- Method selection basis: See Fraction-Negative Method
3. Direct Count Method
- Requires known initial bioburden
- Test Criteria:
- 1 run without sterilant (control)
- 1 run demonstrating ?4-log reduction
- 3 runs with intermediate reduction levels
4. Fraction-Negative Method
- Requires known initial bioburden
- Statistical Models:
- A3.2 HSKP (Holcomb-Spearman-Karber Procedure)
- A3.3 SMCP (Stumbo-Murphy-Cochran Procedure)
Types of Biological Indicators (BIs)
- Strip/Disk BI
Strip/Disk BIMicroorganism-coated carrier (e.g., paper/filter disk) requiring transfer to growth media for incubation. - Ampoule-Based BI
Glass ampoule containing spores and separate growth medium (requires manual crushing to activate).
Self-Contained BI
Integrated unit: Spore strip + growth medium in a single vial (activation by compression).
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