Guiding Principles for Biological Indicators of Sterilization

Biological indicators is a tolerance of certain sterilization program has to determine and stability of the special microorganism manufactured goods, can be used in the performance of sterilization equipment confirmation, specific items of the sterilization process research and development and establishing, product validation of sterilization process, the sterilization effect of monitoring of the production process, the sterilization procedures of periodic revalidation, isolator and sterile clean room validation of sterilization effect evaluation, etc.

The classified biological indicators of biological indicators mainly include the following three types, whose characteristics should meet the requirements of "biological indicators for sterilization of healthcare products" GB18281.
(1) the product is packaged by microbial bud cells and carriers, which can be filter paper, glass, plastic or other materials in the shape of saucer or strip.
The carrier and the inner package shall not contain any physical, chemical or microbial pollutants to avoid affecting the performance and stability of the biological indicator;It shall not be degraded by specific sterilization process;Can be sterilized medium (steam, rays, chemical reagents, filtration, etc.) through and make the sterilization medium and biological indicator can be in full contact.The carrier and packaging shall be designed to ensure that the biomarker is free from contamination, that the microorganism contained in the biomarker is minimally lost during storage, transportation and use, and that sampling, transfer and inoculation are convenient.
(2) the bud cell suspension biological indicator, this kind of biological indicator is suspended in the liquid.For the sterilization of liquid items, it is recommended to determine the number of buds, D value and Z value of the biological indicator in the sterilized liquid items.
(3) a self-contained biological indicator, which is a system consisting of a spore and a culture medium capable of restoring microbial growth.The medium in the system is used to culture the biological indicator after sterilization, and procedures should be developed to ensure that the medium can ensure the growth of residual microorganisms.The tolerance of self - contained biological indicators is for the whole system.

Materials used in self-contained systems should not contain or release during use substances that inhibit the growth of residual microorganisms.The system should be designed to withstand the impact of transportation and use without damage and to minimize the microbial loss of the original inoculation.
Biological indicators basic requirements for microorganisms a biological indicator contains one or two microorganisms that have a clear tolerance to a sterilization pattern.In addition to ionizing radiation, microbial spores have stronger tolerance than bacteria.It is generally believed that bacteria containing spores are more suitable for the preparation of biological indicators.
First draft for comments
Different sterilization processes use different biological indicators, and the microorganism used to prepare the biological indicator should have the following characteristics:

(1) the tolerance of bacteria species should be greater than that of all possible contaminated bacteria in the sterilized articles.
(2) bacterial species should not be pathogenic.The strain should be stable and live for a long time.
(3) easy to save.Easy to cultivate.
(4) the bud cell content of the biological indicator should be more than 90%.

Preparation of biological indicators
Biological indicators should be prepared and controlled according to the procedure.Before preparation, the characteristics of the microorganism used should be determined.
In the preparation of biological indicators, the microorganisms used were cultured, collected and purified on a large scale under appropriate conditions, and then the dormant (ungerminated) bud cells were suspended in the non-nutritive liquid for preservation.The biological indicator should avoid contamination by other microorganisms, and the performance parameters should be determined after preparation.Records of microbial identification and preparation should be established and maintained, including strain origin, identification, traceability of materials and components directly related to biological indicators, passage times, culture medium and its preparation method, data before and after heat treatment, and tolerance of buds (D value and Z value).

Commercialization of biological indicator should have detailed biological indicator of the performance characteristics and instructions, including clear its can be used for the sterilization procedures, culture medium and culture conditions of microorganism after sterilization, the sterilization procedures of tolerance including D value, D value method, stability effect during the period of the total number of microorganisms and tolerance, and storage conditions (including temperature, relative humidity and other storage requirements), the period of validity and the information such as the abandoned measures after use.
The user can also choose the microorganism which can be used as the biological indicator to make the biological indicator for internal use.The user shall determine the purity, number of buds, D value and other parameters of the self-made biological indicator, and set the expiry date to ensure the effectiveness of sterilization verification and monitoring.
Biological indicators should be stored under label or validation conditions, away from light and toxic substances, to prevent overheating and moisture.
Performance evaluation of biological indicators in the validation of the sterilization program, the degree of the biological indicator was killed, is the most intuitive indicator to evaluate the effectiveness of a sterilization program.
The user shall establish acceptance criteria for commercial biological indicators according to the purpose of use to ensure that the performance of biological indicators meets relevant requirements.Before the acceptance of the biological indicator, the D value can be evaluated, and the D value can be determined if necessary. The stability of D value and microbial quantity is particularly important for the long-term storage of the biological indicator.When receiving commercial biological indicators, the identification of microbial purity and morphology and the determination of microbial quantity should be carried out.Biological indicators should be used within the effective period and re-checked for tolerability if necessary.
The properties of the self-made biological indicator should meet the application requirements.
Biological indicator selection
The user shall select the appropriate biological indicator according to the specific sterilization process.The challenge of the biological indicator to the sterilization process must exceed the challenge of the natural microbial load and tolerance inside and outside the product to ensure greater safety of the sterilization process.
Wet and heat sterilization: damp heat sterilization process commonly used biological indicator for thermophilic bacillus coli (Geobacillusstearothermophilus) fat.Other heat-resistant Bacillus, such as Clostridium sporogenes, Bacillus subtilis and Bacillus coagulans biomarkers have also been used for the establishment and validation of the wet heat sterilization process.
Dry heat sterilization: dry heat sterilization process is generally verified by using Bacillus subtilis, but more commonly by depyrogenation method, because the temperature required to remove the heat source is much higher than the sterilization temperature.
Ionizing radiation method: evaluation of the radiation sterilization process the biological indicator Bacillus pumilus was used, but now the dose setting method is generally used to include the evaluation of the initial bacteria before the radiation sterilization and the evaluation of the radiation dose, without the use of biological indicator.In addition, microorganisms have emerged that are more resistant to radiation than bacillus parvus.
Ethylene oxide sterilization: ethylene oxide sterilization process, most commonly using Bacillus atrophaeus biomarkers for validation.
Hydrogen peroxide (VHP) vapor phase sterilization: VHP has been proven to be an effective surface disinfectant or disinfectant.Biological indicators can be used to verify the effect of surface sterilization, generally requiring the number of buds to drop by 3 ~ 6 lg.
Hydrogen peroxide is generally selected steam sterilization process with biological indicator thermophilic fat Bacillus coli (Geobacillusstearothermophilus), also can use hay Bacillus coli, Bacillus subtilis), Clostridium raw spore (Clostridium sporogenes) or other microorganisms.
Biological indicators for hydrogen peroxide steam sterilization processes may use a variety of airtight carrier systems containing glass, metal, or plastic.Materials such as fibrous substrates or other highly absorbent surfaces that readily absorb VHP or water may adversely affect the concentration of VHP used for microbial inactivation, and therefore are not suitable as carriers for VHP biomarkers.

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