Types of biological indicators

Biological indicators (BIs) :

  • Definition of Biological indicators (Bis): According to ANSI/AAMI and ISO, biological indicators (BIs) are test devices containing live microorganisms that exhibit a certain level of resistance to a given sterilization procedure.
  • A biological indicator offers information on whether the parameters were met for a specific sterilization method to kill a given quantity of germs, giving the process a degree of confidence.
  • The microorganisms that are most frequently utilized in BIs are endospores, or bacterial spores.
  • They are regarded as some of the hardest to kill.
  • Different forms of sterilization are more effective against some germs than others. For instance, spore-bearing microbes are more resistant to steam sterilization than non-spore-bearing microorganisms.
  • In order to steam sterilize Spores of Geobacillus stearothermophilus are always employed because of their high resistance, simplicity in cultivation, and lack of pathogenicity (they are thermophiles so they will not grow at body temperature).
  • Biological indicators are offered in many different forms. Examples contain strips (the classic “spore strip”), discs, suspensions, test tubes, and ampoules.
    • Spore strips : when stored at room temperature and pressure, glassine paper, which is used to package spore strips, which are biological indicators, is resistant to moisture and air.
    • Spore Disc: Spore discs are often constructed of borosilicate paper or stainless steel.
    • Spore suspension: Aliquots of spore suspension that are made from a main batch of spores are diluted. Other spore suspensions that are directly applied to surfaces, such rubber closures, as well as test tubes that come in a range of sizes and are typically constructed of glass that resists expansion. Ampoules are little, self-contained vials that are burned shut to create an airtight seal.
  • There are several chemical indicators available that aim to closely resemble the performance of biological indicators. These typically work on the theory that a colour change takes place following exposure to sterilizing circumstances.
types of biological indicators for sterilization
Types of biological indicators for sterilization


Essential Microbiology for Pharmacy and Pharmaceutical Science by Geoffrey Hanlon and Norman Hodges -Wiley-Blackwell Publication.

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