Biological Indicator-Population Verification

What is BI Population Verification?

The Biological Indicator Population Verification test determines the number of spores on a biological indicator (BI) and is typically used to confirm the BI manufacturer’s stated value is representative of the batch. Furthermore, Biological indicators can provide a worst-case plot sterilization method by applying an organism that is resistant to a sterilant used in the specific application. This test can also be used to find out survivors from a sterilization process and calculate lethality rates and D-values.

Why Need BI Population Verification?

Since the population of the BIs can change during shipping or storage, the initial BI Population Verification is necessary. Population count on samples exposed to the sterilant is also important because it provides quantitative data while a BI sterility test only provides results with growth or without growth. In addition, all major pharmacopoeias recommend population verification be performed on each batch of biological indicators. This gives a degree of assurance in the manufacturers stated variables.

Testing procedure

"Sterilization of Healthcare Products - Biological Indicators", ISO 11138, outlines the general requirements and procedures for conducting sterilization or decontamination studies. Procedures often include moist heat, dry heat, ethylene oxide sterilization, low-temperature steam and hydrogen peroxide vapor decontamination. BIs are made up of a standardized and homogenous population of bacterial spores which may vary in type or number, depending on the sterilization or contamination method.

The general procedures for Biological Indicator Population Verification testing include: Using a validated technology to soften BIs in a liquid; Applying a heat shock technique to the softened liquid and diluting the suspension to yield colonies in a certain range of colony-forming units; Plating at last.

Applicable Standards

Both the ISO 11138 and the United States Pharmacopeia (USP) General Chapter <55> give out guidance for conducting biological indicator (BI) population verification testing to determine the number of spores on a BI.

STEMart offers Biological Indicator (BI) Population Verification testing service following the guidance of ISO11138, USP <55>, or manufacturer's instructions. We perform testing on all types of biological indicator configurations such as BI strips, stainless steel sutures, inoculated wires, and spore suspensions. More details on the standards or samples appropriate for your product, please contact us for future information and advice.

If you have additional questions about Biological Indicator (BI) Population Verification testing or would like to find out more about our services, please feel free to contact us.