What are Biological Indicators, Examples, Applications.
What are Biological Indicators- Characteristics, Types, Advantages:
- Biological Indicators are the type of microorganisms that indicate or monitor the health of the environment.
- Bioindicators are the type of microorganisms that indicate or monitor the contamination in the sterilization process.
What are Biological Indicators:
- Biological indicators are the special type of live microorganisms which has resistance power to a specific sterilization process.
- Biological Indicators are also known as Bioindicators.
- Bioindicators are mostly living organisms such as microorganisms, plants, and animals.
- Bioindicators are used to confirm sterilization performance, verify the sterilization procedure, monitor the sterilization effect of the production process, etc.
- For the preparation of biological indicators, it is necessary to determine the characteristics of the microorganisms used.
- Preparation should be carried out according to certain procedures.
- Biological indicators contain a certain number of one or more spores, which attached to carriers, such as filter paper strips, glass slides, culture medium, stainless steel, plastic products, etc.
- To avoid contamination in bioindicators it should be packaged with appropriate materials, sealed in ampoules, and set validity period.
- In the sterilization process, biological indicators are placed in different parts of the sterilization cabinet. And avoid direct contact with the indicator to be sterilized.
- A good bioindicator will indicate the presence of the contamination and also attempt to provide additional information about the amount and intensity of the contamination in the sterilization process.
- The sterilization tolerance of the interested microorganism should be greater than that of all possible contaminating microorganisms in the product to be sterilized.
- The selected microbial strains should be non-pathogenic.
- The strain should be stable.
- It is easy to store.
- It should be a long shelf life
- Easy to cultivate.
- The most commonly used biological indicator for the moist heat sterilization method is Bacillus stearothermophilus spores.
- Spores of Bacillus stearothermophilus, such as ATCC 7953, NCTC 10 007, NCIMB 8157).
- The heat resistance capacity of this bacteria is very high.
- It completely killed at 121℃ for 19 min.
- Clostridium sporogenes spores (Spores of Clostridium sporogenes such as NCTC 8594, NCIMB 8053, ATCC 7955) can also be used as a biological indicator for moist heat sterilization method.
- The most commonly used biological indicator for the dry heat sterilization method is Bacillus subtilis spores.
- Spores of Bacillus subtilis, such as NCIMB 8058, ATCC 9372).
- Escherichia coli endotoxin was used for depyrogenation verification, and the dosage should not be less than 1000 bacterial endotoxin units.
- The most commonly used biological indicator for radiation sterilization method is Bacillus pumilus spores.
- Spores of Bacillus pumilus, such as NCTC 10 327, NCIMB 10 692, ATCC 27 142).
- The number of viable spores per slice was 107-108,
- The microorganisms used for the sterilization process must exhibit greater resistance to radiation than Bacillus pumilus spores.
- Therefore, Bacillus pumilus spores can be used to monitor the sterilization process, but not to establish the sterilization radiation dose.
- The most commonly used biological indicator for filtration sterilization method is Pseudomonas diminuta
- Pseudomonas diminuta such as ATCC19 146, which is used for filters with a pore size of 0.22 μm.
- ATCC 14 756 for filters with a pore size of 0.45 μm.
- It is a method of killing microorganisms by using the gas formed by chemical disinfectants.
- Commonly used chemical disinfectants are formaldehyde fumigation, ethylene oxide, gaseous hydrogen peroxide, atomized hydrogen peroxide, and ozone (O3).
- We know that no matter what gas sterilization method is used, the corresponding biological indicator can be used to evaluate this sterilization method.
(a) Ethylene oxide Sterilization Method:
- For ethylene oxide gas sterilization the biological indicator id Bacillus subtilis spores (ATCC9372) that were sterilized with dry heat was used.
(b) Hydrogen peroxide sterilization method:
- As we know hydrogen peroxide sterilization method is one of the effective methods to remove or kill microorganisms quickly and efficiently.
- The biological indicator used in the verification of the gaseous hydrogen peroxide sterilization method is the same as the moist heat sterilization method.
- Bacillus stearothermophilus spores are most commonly used as a bioindicator for hydrogen peroxide sterilization method (Spores of Bacillus stearothermophilus, ATCC 7953).
- Some commonly used biological indicators for gaseous hydrogen peroxide sterilization are Bacillus stearothermophilus spores, such as ATCC 7953, NCTC 10007, NCIMB 8157.
Biological Indicators | Numbering | Applications/Use |
Spores of Bacillus stearothermophilus | ATCC7953 | Moist heat sterilization validation and gaseous hydrogen peroxide validation |
Spores of Bacillus subtilis | ATCC9372 | Dry heat sterilization method validation Ethylene oxide gas sterilization method validation Ozone gas sterilization method validation |
Spores of Bacillus pumilus | ATCC27142 | Validation of 60Co-γ-ray radiation sterilization method |
Spore of Bacillus subtilis | ATCC12980 | Hydrogen Peroxide Verification |
Pseudomonasdiminuta | ATCC19146 | Filter sterilization validation |
Staphylococcus aureus | CMCC(B)44112 | Validation of Ozone for Cleanroom Gas Sterilization |
Escherichia coli | CMCC(B)44102 | Validation of dry heat sterilization |
Bacillus subtilis | CMCC(B)63501 | Aseptic process simulation test |
Aspergillus niger | CMCC(F)98003 | Aseptic process simulation test |
Clostridium sporogenous | CMCC(B)64941 | Aseptic process simulation test |
Staphylococcus aureus | CMCC(B)26003 | Aseptic process simulation test |
- Biological indicators are used to check the sterilization process, equipment in pharmaceutical processes.
- It is also used for verification of sterilization procedures by gas sterilization and filter sterilization and other physical and chemical methods of sterilization.
- Biological indicators are very important Fermentation and pharmaceutical process verifications, such as Culture Media Sterilization, Bioreactor sterilization, aseptic process simulation test, sterile preparation sealing test, etc.
- The performance of the sterilization process can be monitored by some parameters of the sterilization process, the killing degree of the biological indicator.