MesaLabs
  • Our Solutions

    • Sterilization & Cleaning Monitoring

      • Products

        • Biological Indicators & Accessories

        • Chemical Indicators

        • Cleaning Control

        • All Products

      • Services & Consulting

        • Sterilization Cycle Development & Validation

        • Contract Laboratory Testing

      • Knowledge Center

        • Resource Library

        • White Papers

        • Training & Events

        • Videos

        • FAQs

        • Customer Support

        • Request a Quote

    • Mail-in Spore Testing

      • Products

        • Testing Services Packages

        • In-Office Testing Products

        • Chemical Indicators

        • All Products

      • Services

        • Check Test Results

      • Knowledge Center

        • State Dental Regulations

        • Industry Insights

        • FAQs

        • Customer Support

      • Shop Online

    • Continuous & Process Monitoring

      • Hardware

        • Continuous Monitoring Panels & Sensors

        • Process Monitoring Data Loggers

        • All Products

      • Software

        • Continuous Monitoring Software

        • Continuous Monitoring Software Downloads

        • Process Monitoring Software

      • Services

        • Validation & Calibration Services

        • Data Logger Calibration & Repair

      • Knowledge Center

        • Resource Library

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Renal Care Quality Control

      • Products

        • 90XL Technician Meter

        • pHoenix XL Reference Meter

        • Solutions - Conductivity, pH, Neo Care, NIST-Traceable

        • Care & Calibration Stations

        • All Products

      • Services

        • Equipment Calibration & Repair

      • Knowledge Center

        • Resource Library

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Occupational Health & Safety

      • Gas & Air Flow Instruments

        • Mesa Defender Series (Volumetric Accuracy ±1%)

        • Mesa FlexCal Series (Volumetric Accuracy ±0.5%)

        • Mesa BGI DryCal Metrology Series

        • All Products

      • Accessories

        • Mesa Defender Series Accessories

        • Mesa FlexCal Series Accessories

        • Mesa DryCal Pro Software

      • Services

        • Equipment Calibration & Repair

      • Knowledge Center

        • Resource Library

        • Videos

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Environmental Controls & Air Quality

      • Equipment

        • Mesa BGI Ambient Particulate Air Samplers

        • Mesa BGI Air Flow Calibrators

        • Mesa BGI Personal Sampling Cyclones

        • Mesa BGI Environmental Cyclones

        • All Products

      • Software

        • Mesa BGI Companion Software

      • Accessories

        • Environmental Accessories

        • Industrial Hygiene Accessories

        • Filter Media

      • Services

        • Equipment Calibration & Repair

        • Equipment Rental

      • Knowledge Center

        • Resource Library

        • Videos

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Torque Testing

      • Products

        • Semi-Automatic Torque Testers

        • Manual Torque Testers

        • All Products

      • Accessories

        • Torque Testing Accesories

      • Software

        • TorqueIQ Process Control Software

      • Services

        • Gold Bottle Magnetic Torque Verification

        • Equipment Calibration & Repair

        • Upgrade/Trade-In Options

        • Torque Rentals

      • Knowledge Center

        • Resource Library

        • Customer Support

        • Request a Quote

  • About Us

    • Our Purpose

    • Mesa Brand Family

    • Executive Team

    • Careers

    • Investor Information

  • Contact Us

  • Resource Library

    • Certificate (COA) Finder

    • Regulatory Documents

    • Instruction Manuals

    • Product Specifications

    • Product Technical Reports

    • Safety Data Sheets

  • Our Solutions

    chevron
    • Sterilization & Cleaning Monitoring

      • Products

        • Biological Indicators & Accessories

        • Chemical Indicators

        • Cleaning Control

        • All Products

      • Services & Consulting

        • Sterilization Cycle Development & Validation

        • Contract Laboratory Testing

      • Knowledge Center

        • Resource Library

        • White Papers

        • Training & Events

        • Videos

        • FAQs

        • Customer Support

        • Request a Quote

    • Mail-in Spore Testing

      • Products

        • Testing Services Packages

        • In-Office Testing Products

        • Chemical Indicators

        • All Products

      • Services

        • Check Test Results

      • Knowledge Center

        • State Dental Regulations

        • Industry Insights

        • FAQs

        • Customer Support

      • Shop Online

    • Continuous & Process Monitoring

      • Hardware

        • Continuous Monitoring Panels & Sensors

        • Process Monitoring Data Loggers

        • All Products

      • Software

        • Continuous Monitoring Software

        • Continuous Monitoring Software Downloads

        • Process Monitoring Software

      • Services

        • Validation & Calibration Services

        • Data Logger Calibration & Repair

      • Knowledge Center

        • Resource Library

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Renal Care Quality Control

      • Products

        • 90XL Technician Meter

        • pHoenix XL Reference Meter

        • Solutions - Conductivity, pH, Neo Care, NIST-Traceable

        • Care & Calibration Stations

        • All Products

      • Services

        • Equipment Calibration & Repair

      • Knowledge Center

        • Resource Library

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Occupational Health & Safety

      • Gas & Air Flow Instruments

        • Mesa Defender Series (Volumetric Accuracy ±1%)

        • Mesa FlexCal Series (Volumetric Accuracy ±0.5%)

        • Mesa BGI DryCal Metrology Series

        • All Products

      • Accessories

        • Mesa Defender Series Accessories

        • Mesa FlexCal Series Accessories

        • Mesa DryCal Pro Software

      • Services

        • Equipment Calibration & Repair

      • Knowledge Center

        • Resource Library

        • Videos

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Environmental Controls & Air Quality

      • Equipment

        • Mesa BGI Ambient Particulate Air Samplers

        • Mesa BGI Air Flow Calibrators

        • Mesa BGI Personal Sampling Cyclones

        • Mesa BGI Environmental Cyclones

        • All Products

      • Software

        • Mesa BGI Companion Software

      • Accessories

        • Environmental Accessories

        • Industrial Hygiene Accessories

        • Filter Media

      • Services

        • Equipment Calibration & Repair

        • Equipment Rental

      • Knowledge Center

        • Resource Library

        • Videos

        • FAQs

        • Customer Support

        • Request a Quote

      • Shop Online

    • Torque Testing

      • Products

        • Semi-Automatic Torque Testers

        • Manual Torque Testers

        • All Products

      • Accessories

        • Torque Testing Accesories

      • Software

        • TorqueIQ Process Control Software

      • Services

        • Gold Bottle Magnetic Torque Verification

        • Equipment Calibration & Repair

        • Upgrade/Trade-In Options

        • Torque Rentals

      • Knowledge Center

        • Resource Library

        • Customer Support

        • Request a Quote

  • About Us

    chevron
    • Our Purpose

    • Mesa Brand Family

    • Executive Team

    • Careers

    • Investor Information

  • Contact Us

  • Resource Library

    chevron
    • Certificate (COA) Finder

    • Regulatory Documents

    • Instruction Manuals

    • Product Specifications

    • Product Technical Reports

    • Safety Data Sheets

White Papers

  1. Home

  2. caret-right icon

    Our Solutions

  3. caret-right icon

    Sterilization & Cleaning Monitoring

  4. caret-right icon

    Knowledge Center

  5. caret-right icon

    White Papers

  6. caret-right icon

    VOL 5, ISSUE 4

VOL 5, ISSUE 4

Glassine Packaged Vs. Naked Carrier D-values

By Garrett Krushefski, Scientific & Technical Services Manager

When you go into a restaurant for breakfast your server may ask you “How do you want your eggs?” Your choices are to have them cooked in the shell (soft-boiled or hardboiled) or out of the shell (poached, sunny side up, over easy, over hard, or scrambled). So what does this have to do with D-values? The egg shell is analogous to the glassine envelope of the biological indicator (BI). If the egg is cooked in or out of its shell, the time to achieve the desired result will be different. The same is true for the inoculated spore strip if it is removed from the glassine envelope and processed naked.

The BI is a system that includes:

  • the spores,
  • the carrier material, and
  • the primary packaging.

We occasionally receive requests from our users to perform a D-value on the naked spore strip, removed from the glassine envelope. We don’t recommend this practice. It should be understood that spores do not have an intrinsic D-value. With today’s technology there is no way to test spores suspended in space. The spores must be placed in or on a carrier as a necessary convenience of exposing and recovering them to determine the lethal effects delivered by the process. The carrier has an influence on the observed resistance of the bacterial spore. Any packaging that is placed around the carrier will also impact the observed D-values. ISO 14161:2000, paragraph 5.2 reads, “The strain, the production method, the suspension fluid, the carrier, and packaging materials all affect the resistance characteristics of the finished product.”

Dr. Irving Pflug discusses a phenomena which is now commonly referred to as “the envelope effect” on the carrier in his book “Microbiology and Engineering of Sterilization Processes”, thirteenth edition, 2008. Dr. Pflug emphasizes that the spores plus a carrier plus a glassine envelope constitute a system. It is the system that is evaluated when a BI is tested.

Pflug states, “With the arrival of the era of validation, about 1975, to measure the localized effort of the sterilization process, technologists, on occasion, removed the spore strip from the envelope and placed the spore strip (“naked”) in or on a product.” The performance observed was not always that which was expected. Pflug observed that when the spore strip was removed from the envelope and placed into a flask of TSB medium, the exhibited D-value was different from the spore strip in its glassine envelope exposed to the same process. Pflug (2008) reported the following D121°C-value results:

  1. Strip in envelope - 1.45 minutes
    Strip in 10 ml TSB & BCP - 3.94 minutes
  2. Strip in envelope - 0.82 minutes
    Strip in 10 ml TSB & BCP - 1.85 minutes

Pflug (2008) also discussed another experiment in which spores from suspension were tested in three different configurations. They included spore strips in glassine envelopes heated in steam, spore strips deposited in and heated in liquid and spores directly inoculated into and heated in liquid.

  Strips in Envelope Naked Strips in Liquid Spores in Liquid
D121 1.39 minutes 2.50 minutes 4.30 minutes

 

Mesa has performed experiments using glassine-packaged and naked strips directly exposed in steam and ethylene oxide (EO) Biological Indicator Evaluator Resistometers (BIER). The naked strips exhibited a higher D-value than that observed in the envelope when exposed to steam. The opposite trend was observed for EO testing.

  Strips in Envelope Naked Strips
D121 Steam 2.2 minutes 3.1 minutes
DEO 4.1 minutes 0.3 minutes

 

Mosley, Gillis and Whitbourne (2002) presented DEO values for naked spore carriers embedded into medical devices

Device DEO (minutes)
Canula 5.29
Unassembled bone harvesting device <6.19
Injectable polymer system 4.09
Rotor blade 4.16
Suture anchor 4.00

 

This data clearly indicates that each specific configuration which includes spores plus carrier plus package is a unique system and will exhibit unique observed resistance performance. The resistance of an embedded naked spore strip in a medical device does not compare to, nor have any relevance to the resistance value that would prevail for the naked strip (or the glassine packaged strip) exposed in a BIER. The device carrying the naked spore strip becomes part of its own unique system. This system will have its own unique resistance. Addressing this subject, ISO 14161:2000, paragraph 7.2 states, “Placement of the biological indicator either within the product or within the load is likely to alter its apparent resistance characteristics in comparison to the resistance noted on the labeling of the biological indicator.”

Still not convinced? Considering the following study in which naked spore strips inoculated with 2.9 X 102 Bacillus atrophaeus spores per strip were inserted into the manifold set at the locations identified in Figure 1. When tested in a BIER, the naked strip D-value was 0.4 minutes; the glassine packaged D-value was 3.2 minutes.

The strips at locations 9 & 10 were killed in a 20 minute exposure (the shortest time tested), thus indicating a D-value of ≤ 5.8 minutes. The strips at locations 1, 5, 6 & 7 required an 80 minute exposure for complete kill, thus indicating a D-value of ~ 23.1 minutes. The strips at locations 3 & 4 required a 160 minute exposure for inactivation, indicating a D-value of ~ 46.2 minutes. The strip at location 8 required a 320 minute exposure for inactivation, indicating a D-value of ~ 92.4 minutes. The strip at location 2 was always positive for growth, even in the longest test exposure of 320 minutes, which suggests a D-value in excess of 92.4 minutes! (What is more likely is that no sterilizing agent was reaching this location, by virtue of the closed stop cocks, and the spores on the strips would survive no matter what exposure time was selected.)

Figure 1 Bacillus atrophaeus spores

Recall that the D-value for the naked test strips was 0.4 minutes and the glassine-packaged D-value was 3.2 minutes. Which is more relevant to the customers intended use in the angiographic set? NEITHER!

If neither D-value has relevance, why test D-value at all? In such circumstances, the labeled D-value on the Certificate of Analysis can only be used as a bench-mark means for comparing lot-to-lot differences in future product received. Mesa selects to test and report the glassine packaged D-value for several reasons:

  • Testing the glassine packaged strips is less susceptible to post exposure contamination, which would lead to false positives in the fraction negative data set.
  • As a result of the aforementioned, the resulting D-value will be more accurate and reproducible which will facilitate future lot-to-lot comparison of newly received strips.
  • Assessment in glassine is easier and less labor intensive; both of which help to keep production costs down which in turn, keeps the price of product affordable.

Mesa provides its customers with quality products at affordable prices. In this case, the assessment in glassine provides the most accurate and reproducible “bench-mark” resistance value in a situation where neither value (glassine or naked assessed) is applicable to the sterilization cycle.

As a user you need to have a well controlled reference system to evaluate spore resistance performance. The glassine envelope and paper carrier has served as a reference system for decades. Resistance testing the naked carrier in a BIER will provide a D-value that has no relevance to the performance when embedded into a device.

SPORES DON’T LIE®

Topics: Ethylene Oxide ,   Failure Investigation ,   BI Selection ,   Steam ,   Dry Heat ,   Resistance ,   Incoming Inspection ,   Label Claim Validation
Recent Posts
Why BIs Survive a Validated Cycle A Review of the Newly Released ISO 11138-8 Standard on the Validation of a Reduced Incubation Time for Biological Indicators Product D-Value Study - Part 2, Heat-sensitive & Atypical Aqueous Liquids Why perform a Product D-value Study? Part 1 The MeCo Solution: Improving Consistency, Accuracy and Robustness in SIP Validation Sub-culturing a Positive Biological Indicator for Identification Biological Indicators and the European Pharmacopoeia

Subscribe now

Full of expert takes on industry trends and the latest technical education offerings. Spore News gives you the insight you need to prepare for what's next.

MesaLabs

Our Solutions

  1. Sterilization & Cleaning Monitoring
  2. Mail-In Spore Testing
  3. Continuous & Process Monitoring
  4. Environmental Controls & Air Quality
  5. Occupational Health & Safety
  6. Renal Care Quality Control
  7. Torque Testing

About us

  1. Our Purpose
  2. Mesa Brand Family
  3. Executive Team
  4. Careers
  5. Investor Information
  1. Sterilization & Cleaning Monitoring
  2. Mail-In Spore Testing
  3. Continuous & Process Monitoring
  4. Environmental Controls & Air Quality
  5. Occupational Health & Safety
  6. Renal Care Quality Control
  7. Torque Testing
  1. Our Purpose
  2. Mesa Brand Family
  3. Executive Team
  4. Careers
  5. Investor Information
  1. Contact Us

    Corporate Headquarters
    Mesa Laboratories, Inc.
    12100 West 6th Ave.
    Lakewood, CO 80228

    303.987.8000
    customerservice@mesalabs.com

Connect with us

Follow us on Facebook Follow us on LinkedIn Follow us on Twitter Follow us on Facebook
©2022 Mesa Labs, Inc. All rights reserved. |   Terms, Conditions & Privacy Policy   |   Cookie Settings
©2022 Mesa Labs, Inc. All rights reserved. Terms, Conditions & Privacy Policy