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 6, ISSUE 2

VOL 6, ISSUE 2

The Biological Indicator Spore Population has Minimal Impact on Resistance Performance

By Garrett Krushefski, Scientific & Technical Services Manager

Mesa Laboratories receives many requests from customers for very specific spore populations on the BIs. These requests, in many cases, are a result of purchase specification requirements established by well meaning individuals. Requirements that significantly influence product performance qualities are essential. Some purchase specification requirements simply make the product more expensive, may delay orders or create other issues for both the manufacturer as well as the user. Many times these requirements don’t provide the user with the product qualities really needed which is consistent performance in monitoring the sterilization process. Mesa makes every attempt to honor these requests and our customers’ needs. We recently had to delay a customer’s order because a population assay was 2.1 x 106 and the purchase specification required a population between 1.5 x 106 and 2.0 x 106 . The customer had to wait three weeks for a new lot to be made and Mesa incurred all associated manufacturing fees to produce a lot that would meet the purchase specification. As you will see, neither of these inconveniences (delay or cost) was necessary.

The point of this Spore News is “prepare your purchase specifications based on sound science” and not an emotional feel good value. First, let us consider the spore population label claim verification testing. USP1 and ISO state that recovery values within 50% to 300% of the label claim are acceptable. This may seem like a HUGE range until one considers the overall impact this would have on the resistance performance for the indicator. It is relatively easy to mentally calculate the lower limit (LL) and upper limit (UL) using the ISO method. For that reason, the calculation using the USP method (see footnote) follows:


[1] USP 32 reads, “The requirements of the test are met if the log average number of viable spores per carrier is not less than 0.3 log of the labeled spore count per carrier and does not exceed the log labeled spore count per carrier by 0.48.” Mathematically, this is equivalent to the ISO requirement of 50% to 300%.

LL = (Log102.0 × 106) - 0.3

LL = 6.3 - 0.3 = 6.0; converted back to scientific notation,

Inverse Log of 6.0 = 1.0 × 106

UL = (Log102.0 × 106) + 0.48

UL = 6.3 + 0.48 = 6.78; converted back to scientific notation,

Inverse Log of 6.48 = 6.0 × 106

Again, the difference between 1 million and 6 million spores seems quite large. But as we will soon see, the difference is quite insignificant.

Table 1 outlines the spore death kinetics for three theoretical BI lots with spore populations of 1 million, 2 million and 6 million spores per BI. Each lot has a 4.0 minute DEO-value.

three-lots-identical-d-values-table

Note that despite the number of spores present on each strip, all 100 test strips from each of the three lots would be killed in the 36.0 minute exposure. At all shorter exposures, positives would be observed. From a user standpoint, any of the three lots could be used to monitor a sterilization cycle and virtually no difference would be detected. The subtle differences in the number of positive units as shown in this table could only be detected in a BIER (biological indicator evaluator resistometer) which is designed to deliver tightly-controlled, distinct “doses” of lethality.

While zero positives are expected for any of the lots when exposing 100 strips in the 36 minute cycle, we can calculate the percent chance for survival using the following equation.

formula-1-negative-units-per-100-exposed

Thus, for Lot B the chance for a BI to test positive from the 36 minute exposure is:

formula-2-negative-units-per-100-exposed

Thus, one will have 99.8 negative units per 100 exposed; or a 0.2 % chance for any individual strip from Lot B to test positive after having been exposed to the 36 minute exposure.

  • For Lot A, there is a 0.1% chance for a positive BI from the 36 minute exposure.
  • For Lot C, there is a 0.6% chance for a positive BI from the 36 minute exposure.

We now see how the seemingly large difference in 1 million or 6 million spores per BI is reduced to an insignificant difference in potential for survival.

The following is a graphical representation of the relevant spore death kinetics.

spore-population-exposure-time-chart

All of the above discussion was based upon theoretical BIs. Let us now look at three actual lots to see how difficult they are to kill.

  • The spore population for BATR-352 is 2.8 X 106 , DEO-value = 4.2 minutes.
  • The spore population for BATR-361 is 3.3 X 106 , DEO-value = 3.8 minutes.
  • The spore population for BATR-365 is 8.3 X 106 , DEO-value = 3.4 minutes.

So, which lot will be the easiest to kill? The answer may surprise you, although well read Spore News readers will have an advantage in correctly answering that question (i.e. see Spore News Volume 4, Number 3, May 2007).

The answer… BATR-365 with its 8.3-million spores is the easiest to kill!

Table 2 presents the resistance performance data that appears on the Certificate of Analysis for each lot.

table-comparison-reistance-performance

The graph below presents the log-linear death curve for each lot from Table 2. Examination of the graph helps to illustrate how it is possible that a strip with more than twice as many spores as either of the other two will be inactivated first.

spore-population-exposure-time-chart-2

The purchase specification is intended to secure a product that will provide you with a consistent challenge for monitoring your sterilization process. Performance is the key and spore population is one element that influences it, but only one. Similar to a jigsaw puzzle, you can not see the whole picture by focusing on one piece. Spore population on the BI is only one piece of the sterilization puzzle.

SPORES DON’T LIE®

Please email us with topics you would like to see addressed in “Spore News”.

Topics: Ethylene Oxide ,   H202 Sterilization (Vacuum Assisted) ,   BI Selection ,   Steam ,   Dry Heat ,   Resistance ,   Population
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