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【 Micro Classroom 】 Basis for determining the cultivation cycle of biological indicators
Date: 2025-07-30Read: 0
According to GB/T18281.1-2024The cultivation time of biological indicators for sterilization of healthcare products is generally 7 days. However, when receiving finished biological indicators,You may find that the cultivation time for biological indicators indicated on the instruction manual is 7 days, 48 hours, 24 hours, or even shorter, 3 hours, 30 minutes. How are these cultivation times less than the requirements determined?
Shortening the cultivation time of biological indicators should be based onISO 11138-8：2021《Sterilization of health care products — Biological indicators —Part 8: Method for validation of a reduced incubation time for a biological indicatorHow to translateConduct experiments and confirm the shortest cultivation time based on the experimental results. The equivalent substitute national standard for this standard is
The "Sterilization Biological Indicators for Healthcare Products Part 8: Confirmation Methods for Shortening the Cultivation Time of Biological Indicators" was released in November 2024 and will be officially implemented in June 2026.For exampleTaking the shortened cultivation time test results of Tailin SS6-121 self-contained pressure steam sterilization biological indicator as an example
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We will provide a detailed explanation on how to confirm the shortened cultivation time of biological indicators.
Confirm the sterilization conditions for the biological indicator during the partial cycle, so that the biological indicator is sterilized during this cycle. After 7 days of cultivation, it is expected that 30% to 95% will show positive results.
Sterilize the batch of biological indicators to be tested in a resistance tester at 121 ℃ for 16 minutes. After 7 days of cultivation, the positive rate of the biological indicators is 70%, indicating that the sterilization time meets the expected requirements; If the positive rate of the biological indicator after 7 days of cultivation under the same conditions is lower than 30% or higher than 95%, it is considered that the sterilization time does not meet expectations and needs to be adjusted to ensure that the positive rate of the biological indicator after sterilization is between 30% and 95%; Table 1 introduces the screening process of the sterilization time for this biological indicator. When the sterilization time is 16 minutes, the positive rate of the three batches of biological indicators is between 40% and 65%, all of which meet the requirements. The subsequent sterilization conditions can be confirmed as 121 ℃ for 16 minutes.
Take 3 batches of this product, with 100 biological indicators per batch, and kill them according to the sterilization time confirmed in step (01), that is, sterilize at 121 ℃ for 16 minutes in the resistance tester.
After the sterilization is completed, perform inoculation according to the instructions and transfer to the specified culture conditions for 7 days. Record the positive and negative results of the biological indicator at predetermined time intervals. For example, the set time interval is 24 hours, and the results are recorded every 24 hours. The final cultivation time result is measured in hours. The test results are shown in Table 2.
At the same cultivation time interval, the correlation between the number of positive biological indicators in 3 batches and the number of positive biological indicators on the 7th day is ≥ 97%, that is, the "growth ratio" in Table 2 is ≥ 97%, which can be confirmed as the shortest cultivation time. The calculation formula is as follows:20According to Table 2, the growth ratio of both the first and second batches of indicators was less than 97% after 24 hours of cultivation, and "24 hours" cannot be used as the shortest cultivation time; When the cultivation time is 48 hours, the growth ratio of the three batches of biological indicators is 100%, which meets the requirement of "≥ 97%" in the standard. Therefore, 48 hours can be selected as the final cultivation time for this biological indicator. Therefore, the instructions for the Tailin SS6-121 self-contained pressure steam sterilization biological indicator indicate a cultivation time of 48 hours.At present, this method is widely used in medical devices, hospitals, and other fields, such as rapid biological indicators (with a cultivation time of generally 3 hours) and rapid biological indicators (with a cultivation time of generally 30 minutes). The confirmation of positive results of these biological indicators is mainly achieved by detecting the fluorescence intensity of the biological indicators.23rd edition of Drug GThe MP Guidelines clearly state that,ISO 11138-8：2021《Sterilization of health care products — Biological indicators —Part 8: Method for validation of a reduced incubation time for a biological indicator
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