Blood bag sterilization verification: How do biological indicators Ensure that sterilization Effects Meet standards

In the sterilization validation of blood bags, biological indicators ensure that the sterilization effect meets the standard in the following ways:

1. Select the appropriate strain: For different sterilization methods, select strains with greater tolerance than the possible contaminating microorganisms in the sterilized products. For example, in moist heat sterilization, the most commonly used biological indicators are thermophilic Bacillus stearothermophilus spores, such as NCTC10007, NCIMB8157, and ATCC7953, with a D value of 1.5-3.0min, and the number of live spores per piece (or bottle) is 5×10⁵-5×10⁶, which should be completely killed at 121℃ and 19min.

2. Determine spore tolerance: In the biological indicator validation test, it is necessary to determine the tolerance of spores under actual sterilization conditions, and determine the purity and number of spores. During validation, the amount of microorganisms used in the biological indicator should be larger than the amount of microbial contamination detected daily, and the tolerance should be strong to ensure greater safety of the sterilization procedure. 3. Scientific placement of biological indicators: Before sterilization, place the biological indicator inside or in a representative position of the sterilized object to ensure that it can be fully exposed to the sterilization environment. For example, in the terminal sterilization method, the biological indicator should be placed in different parts of the sterilization cabinet, and avoid direct contact between the indicator and the sterilized object. 4. Standardized culture and observation: After sterilization, the biological indicator is taken out and cultured under appropriate culture conditions. Different biological indicators have different culture conditions. Generally, bacterial spore biological indicators need to be cultured at 37°C or 56°C for 24 hours to 7 days. The results are judged based on the changes in the indicator system. For example, if the color changes from purple to yellow, it usually indicates that there is microbial growth and sterilization has failed; if the color remains unchanged, it indicates that the sterilization is successful. Some biological indicators also display results by other means such as fluorescence. 5. Perform biological indicator challenge tests: prove that the developed sterilization procedure actually reaches the biological killing time determined in the program design. Select an appropriate biological indicator system. In the confirmation of the overkilling procedure, the cycle ends with F₀>12, and the D₁₂₁℃ of the biological indicator should be greater than 1. Bacillus stearothermophilus is often used. In the confirmation of the sterilization procedure designed using the "residual probability method", the heat resistance of the biological indicator should be greater than the heat resistance of the product's bioburden, and it is necessary to combine the historical data of the bioburden to leave a certain safety factor. 6. Set up controls and evaluations: The biological indicator challenge test should be a positive control, and confirm that the number of biological indicators at the inoculation site is sufficient and there is no other interference. Evaluate the results to ensure that the logarithmic reduction value of the spores in the test meets the predetermined requirements and meets the product microbial survival probability PNSU less than 10⁻⁶.