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Sterilization Indicators

Chapter 3: Table of contents

 A variety of sterility indicators are available for use in identifying successful sterilization.  

Steam Tape

Chemical indicators are most commonly used in veterinary medicine to indicate that sterilization has occurred.  They are often in the form of tape or paper strips that are included on or in the pack during sterilization.  The chemicals in the indicator change colour when they reach a certain temperature, indicating only that the appropriate temperature was achieved at one point during sterilization; therefore, such indicators can suggest appropriate sterilization when a load reaches the correct temperature but for an inappropriate period of time.  Chemical indicators do not indicate the duration of exposure to the correct temperature and pressure, and therefore do not confirm the sterility of the pack.   

  • Steam Indicator Strip:  Steam indicator strips are commonly used in veterinary medicine to indicate sterilization has occurred.  The strips can be placed within packs to ensure the appropriate temperature was reached in the center of the pack. The chemicals in the indicator generally turn from white to black when they reach a certain temperature, indicating only that the appropriate temperature was achieved at one point during sterilization.  Steam indicator strips do not indicate the duration of exposure to the correct temperature and pressure, and therefore do not confirm the sterility of the pack.
  • Steam Tape:  Steam tape is a chemical indicator commonly used in veterinary medicine to indicate sterilization has occurred.  The tape can be used to seal packs and as labels to mark the date and the initials of the individual who prepared it.  The chemicals in the indicator turn black when they reach a certain temperature, indicating only that the appropriate temperature was achieved at one point during sterilization.  Steam tape does not indicate the duration of exposure to the correct temperature and pressure, and therefore does not confirm the sterility of the pack. 
  • Plasma Indicators:  Plasma indicator tape and strips are placed on and in packs prepared for plasma sterilization.  The strips can be placed within packs to ensure the vapour penetrated the center of the pack.  The chemicals in the indicator generally turn from red to yellow when they react with hydrogen peroxide, indicating only that the indicator was exposed to the vapour at one point during sterilization.  Plasma indicators do not indicate the duration of exposure to the vapour, and therefore do not confirm the sterility of the pack.

Biological indicators are the most accurate method of detecting proper sterilization.  Highly resistant bacterial spores (Bacillus subtilis var. globiigi for ethylene oxide, Bacillus subtilis var. niger for plasma sterilization and Bacillus sterarothermophilus for steam sterilization) are stored in a container that is sterilized with the instruments and then cultured to determine if any bacterial growth is present.  The disadvantage to this method is the length of time required to wait for results (1-7 days) and also increased cost.

Biological Indicators

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