Selection and Use of Biological Indicators during Validation Studies

Sample Document

Table of Content:

  1. Purpose
  2. Scope
  3. Definitions
  4. Sterility Assurance level (SAL)
  5. Probability of a Non-Sterile Unit (PNSU)
  6. Responsibilities
  7. Standard
  8. General
  9. Biological Indicators
  10. Use of Biological Indicators
  11. Wrapping Procedure of the Biological Spore Strips
  12. Storage Conditions of Biological Indicators
  13. Transport of Biological Indicators
  14. Disposal of Biological Indicators
  15. QC Testing of Biological Indicators
  16. References
  17. Appendix 1: Biological Indicator Test Results Sheet – Glass Ampoules
  18. Appendix 2: Biological Indicator Test Results Sheet
  19. Appendix 3: Biological Indicator Test Results Sheet – Spore Strips

Sample Content

Purpose

The use of Biological Indicators (BI’s) for the validation and in-process monitoring of sterilisation cycles is becoming increasingly complex and highly regulated. Therefore, a defined approach to the use and control of biological indicator validation exercises is required. The purpose of this Standard Operating Procedure is to define the selection and usage of Biological Indicator Spore Strips and ampoules when validating thermal processes or equipment.

Scope

The biological indicators defined in this SOP are applicable for the validation and monitoring of sterilisation cycles utilised at a GMP site, in the production of biopharmaceutical products. The usage procedures defined in this SOP shall apply to all validation activities carried out at a GMP site using biological indicator spore strips for process and equipment validation or testing work.

Definitions

D value: The time taken, in minutes, to reduce a population by 90% (one Log10). This term is usually followed by a reference to the sterilisation modality concerned, in sub-script; thus for steam it is D121, for dry heat D160 and so on.

Z value: The change in temperature required to change the D-value by one Log10. i.e. A Z value of 10°C will change a D value of 5 minutes at 121°C to a D value of 0.5 minutes at 131°C

F0: The equivalent time, in minutes, at 121°C, calculated from time(s) at different temperatures, assuming a Z value of 10 °C. Used to include heat up and cool down times in cycle lethality calculations.

Time/Temperature Sterilisation: A sterilisation cycle based on a load being held at a set temperature for a set amount of time. For example, an autoclave cycle of fifteen consecutive minutes at a minimum temperature of 121°C.

Bioburden: The term used to encompass the total biological challenge to a process. Usually, but not exclusively, referring to those organisms recovered from the product matrix prior to sterilisation.

Lethality Input (LI): An estimation of the process challenge calculated from the D value and the population of the BI.

Example:

Lethality input = Log10 population of BI x D Value of BI

Example = Log10 1.7 x 106 x 1.95 minutes = 6.23 x 1.95

LI = 12.15

The Lethality Input is to be used to record the challenge to a sterilisation process and to ensure that future validation activities use an equivalent challenge to the process.

Lethality Input is also known as Fbiological or Fbio.

Sterility Assurance level (SAL): Probability of a single viable micro-organism occurring on an item after sterilization.

Note: The term SAL takes a quantitative value, generally 10-3 or 10-6. When applying this quantitative value to assurance of sterility, an SAL of 10-6 takes a lower value but provides a greater assurance of sterility than an SAL 10-3.

Probability of a Non-Sterile Unit (PNSU): The probability of a unit (product container) being non-sterile after the application of a lethal agent. The distinction between SAL and PNSU is that non-sterile units may have more than a single surviving micro-organism.

Sample Document