Applications of Biological Indicators

Applications of Biological Indicators

In sterilization process validation, while certain parameters can be used to evaluate sterilization effectiveness, the degree of spore inactivation in biological indicators serves as the most direct measure of a sterilization program’s efficacy.

Biological indicators can be:

• Commercially available standard biological indicators, or
• Custom-prepared spores from the most resistant microorganisms isolated through routine production contamination monitoring.

Validation Process

During biological indicator validation, several key factors must be determined:

1. The D-value of spores under actual sterilization conditions.
2. The purity and quantity of spores.

To ensure safety, the microbial load in the biological indicator should be higher and more resistant than common environmental contaminants. Sterilization programs must exceed normal contamination levels to ensure effectiveness.

Placement in Final Sterilization

• Biological indicators should be strategically placed in various locations within the sterilization chamber.
• Direct contact with sterilized items should be avoided.
• After sterilization, indicators should be removed and incubated in a culture medium to confirm complete inactivation of spores.

Overkill Validation Approach

• Overkill validation does not consider routine microbial contamination levels and can rely on commercially available biological indicators.
• For products with low resistance to sterilization methods, a sterilization process should be designed based on:
  • Expected microbial contamination levels in production,
  • Selection of microorganisms and spore counts for biological indicators.

Sterility Assurance

For low-resistance products, sterility assurance should be achieved through:

1. Monitoring microbial contamination before sterilization,
2. Assessing resistance levels,
3. Evaluating data obtained through sterilization process validation.