White Papers | Sterilization & Cleaning Monitoring | Mesa Labs

Biological Indicator Spore Population and Resistance Performance | Mesa Labs

Written by Mesa Labs | Dec 20, 2024 9:26:41 PM

By Kurt McCauley

Mesa PCDs are unique, patented devices containing spore strip/disc biological indicators (BIs) or self-contained BIs (SCBIs) for use in challenging ethylene oxide (EO) sterilization processes. The simplistic design and wide-ranging resistance performance greatly assist the sterilization scientist in process development, validation, and routine monitoring activities.   

Each PCD consists of a BI packaged into a single-use pouch designed to correspond with the performance of the BI embedded into the product.  There are several options, each with an increasing level of resistance to the sterilization process allowing the user to select the appropriate pouch type to optimize their sterilization process.  The basic construction of each PCD includes:

  • Product Label: Polyolefin plastic with removable pressure- sensitive culturing label.
  • Mounting Card: PVC plastic with a pressure-sensitive adhesive strip for mounting on the outside of a sterilizer load.
  • EO Resistant Barrier Pouch: Proprietary multi-layer plastic film combinations result in consistent EO sterilization
    resistance.
  • Biological Indicator: Spore strip, Spore disc, or SCBI meeting ISO 11138-2 requirements.
The PCD Selection Guide¹ provides additional details on the numerous configurations and their relative resistances.  
Mesa PCDs can be used both internally and externally with the load, designated as IPCDs or EPCDs respectively.  The IPCD is placed inside the load as a surrogate for inoculated product (used during process development and validation), while the EPCD is placed on the outside of the load as a surrogate for the IPCD.
The EPCD is used during routine operation, thereby eliminating the need to dismantle or penetrate the load for retrieval².

Historically PCDs used for EO sterilization were produced in-house consisting of BI-embedded-product or other
similar devices. These types of PCDs are often used repeatedly and can be problematic for several reasons. They can be costly in their preparation and non-uniform in their performance due to variability in components, assembly, and potential compromise due to repeated manipulation.
 
Mesa PCDs are consistent in their performance due to the tightly controlled components and manufacturing processes. Because Mesa PCDs are easily mounted externally on the load, they not only minimize employee exposure to harmful EO gas during recovery, but they also reduce recovery costs since retrieval of the EPCDs can be accomplished in seconds. In addition, the PCDs are available with SCBIs which permit quicker time-to results, thereby expediting the movement of product inventory in the pipeline.
 
The most common method for cycle development is the Overkill approach which is detailed in ISO 11135. The use of Mesa PCDs in conjunction with this method is presented in the Mesa-published documents Choosing a PCD-Configuring for Your Cycle³ and PCD Validation Guide4. These documents provide direction in selecting the PCD with appropriate resistance to your process.
 
Mesa has developed the Selection Set5 to assist the user in finding the appropriate EPCD for use in routine monitoring of the sterilization process. The set consists of 4 PCDs, each with increased resistance to the process. The set is used during validation activities for the purpose of determining the most appropriate EPCD to use for optimizing the process. The PCD in the Selection Set that provides equivalent or slightly greater resistance as compared to the IPCD is the appropriate selection.
 
In summary, Mesa PCDs are the right choice when developing and validating new EO sterilization processes or optimizing existing cycles, the latter of which is desirable as this will reduce EO consumption and minimize potential exposure to both workers and the environment.
 
Reference Documents 
 
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