Small Knowledge about Sterilization Monitoring Indicators for Autoclaves

A good sterilization method is crucial for ensuring biosafety in the laboratory, the success of experimental results, and even personal safety. Then, how can we assess whether the sterilization work we have done is effective?
I. Chemical indicators

1. Principle:
   Chemical indicators will change color or deform when heated under a certain temperature and exposure time. This characteristic is used to determine whether the required sterilization parameters have been achieved.
2. Classification:
   Category 1: external chemical indicator tape
   It is affixed to the outside of each package containing items to be sterilized.
   Purpose: Sealing the package;Recording sterilization information;Serving as a marker for sterilization processing.
   Category 2: chemical indicators
   They refer to chemical indicators designed for specific testing procedures.
   Purpose: Used for the Bowie-Dick Test (BD Test).
   Category 3: Single-parameter indicators
   Purpose: Chemical indicators that respond to only one critical parameter during the sterilization process.
   Category 4: Multi-parameter indicators
   Purpose: Chemical indicators that respond to two or more critical parameters during the sterilization process.
   Category 5: Integrating Indicators
   Purpose: Chemical indicators that respond to all critical parameters within a specific cycle range during the sterilization process.
   Category 6: Emulating indicators (or cycle-specific indicators)
   Purpose: Indicators that respond to all critical parameters of a specific sterilization cycle.
   II. Biological indicators
3. Principle:
   A certain quantity of heat-resistant spores with known characteristic values is sterilized under specified moist heat sterilization conditions to verify whether the established sterilization process can indeed ensure that the product meets the predetermined sterility assurance level.
4. Main classification:
   Category 1: carrier-based biological indicators
   Composed of microbial spores and a carrier, which are packaged together.
   Purpose: This type of indicator is relatively suitable for verifying and monitoring the sterilization process of non-solution items.
   Category 2: spore suspension biological indicators
   Spores are suspended in a liquid.
   Purpose: Mainly used for verifying the sterilization of liquids in moist heat sterilization, and are applied by being placed in the liquid.
   Category 3: self-contained biological indicators
   Consist of spores and a medium system capable of supporting microbial growth.
   Purpose: Mainly used for verifying saturated steam sterilization in moist heat sterilization. When a steam sterilizer is used to sterilize culture media, reagents, and laboratory utensils, the sterilization effect must be regularly verified using self-contained biological indicators.
   Currently, there are three main methods for determining the effectiveness of pressure steam sterilization: physical monitoring, chemical monitoring, and biological monitoring. Among them, biological monitoring is currently the most effective and reliable method for evaluating the effect of high-pressure sterilization.