Biological Indicators contains microorganisms that are used as a control in a sterilization process. Biological Indicators directly measure the lethality of a sterilization cycle.
Biological indicators (BI) are trusted by hospitals, healthcare & research laboratories, pharmaceutical and medical device manufacturers, CSSD/CSSU, dental clinics and more, in enabling the validation and verification of a sterilization cycle.
Biological Indicators are the most accepted method for monitoring the sterilization process due to its ability to assess the ability of the sterilization process to kill highly resistant microorganisms.
The microorganisms used in a biological indicator are more resistant and numerous than the microorganisms found on the product being sterilized. An inactivated biological Indicator means that other microorganisms in the load have been killed.
The Centers for Disease Control and Prevention (CDC) recognizes biological indicator to be ideal sterilization monitors that should be in used in conjunction with mechanical and chemical indicators.
Below are several types of Biological Indicator application:
1. Steam sterilization
Typically, it is the process of exposing the item directly on the steam by using the autoclave at certain temperature and pressure for sterilization. The biological indicator is there to ensure the correct combination of time, temperature, and saturated steam.
2. Ethylene oxide (EO) sterilization
The basic EO sterilization cycle consists of five stages (preconditioning and humidification, gas introduction, exposure, evacuation, and air washes) and takes approximately 2 1/2 hours excluding aeration time. Biological indicators are used to help medical device manufacturers and contract sterilization providers confirm EO sterility assurance efficiently and accurately.
3. Dry heat sterilization
The dry heat sterilization process is accomplished by conduction; that is where heat is absorbed by the exterior surface of an item and then passed inward to the next layer. Dry heat destroys microorganisms by causing denaturation of proteins. The biological indicator is used to help determine the correct amount of time and temperature is used during the sterilization process.
4. Hydrogen peroxide (H2O2) sterilization
Liquid H2O2 gets converted into vapor. The vapor fills the chamber, contacting all surfaces and penetrating lumens. After sterilization, the vapor is vacuumed from the chamber and converted into water and oxygen. The biological indicator will determine if sufficient amount of H2O2 is used during the sterilization process.
5. Gamma irradiation sterilization
Gamma irradiation is a physical/chemical means of sterilization, because it kills bacteria by breaking down bacterial DNA, inhibiting bacterial division. Energy of gamma rays passes through the equipment, disrupting the pathogens that cause contamination. The biological indicator will determine if the amount of time of the gamma irradiation is sufficient to kill the bacteria inside the biological indicator.
The type/form of indicators available:
1. EZTest vials
EZTest® is easy-to-use and produces visual results within 24 hours (steam or hydrogen peroxide) or 48 hours (ethylene oxide) without laboratory transfers.
2. Spore strips
Spore strips for steam sterilization processes consist of bacteria spores inoculated on filter paper with the size of 6 x 38 mm and packaged in glassine envelopes. They are available in two different populations, inoculated with Geobacillus stearothermophilus
MesaStrip is a conventional paper strip biological indicator for monitoring steam, low temperature steam, ethylene oxide, dry heat, chlorine dioxide, ozone and gamma radiation industrial sterilization processes.
4. Industrial Use (cotton thread, paper disc, stainless steel)
Standard Biological Indicators (BIs) are easy to use and are available for industrial or healthcare use. However, some manufacturing situations require a modified or specialty Biological Indicator to assist in validating the sterilization process. Manufacturers and validation specialists require unique tools where spore strips and ampoules are not suitable because of size, packaging or carrier material.
5. Process challenge devices (PCD)
Process challenge devices (PCDs), according to ANSI/AAMI/ISO TIR11139:2006—Sterilization of health care products—vocabulary, are devices “designed to constitute a defined resistance to a sterilization process and used to assess performance of the process.
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