The spore population on the Certificate of Analysis is reported as the heat shocked population per unit (biological indicator) with the exception of spore suspensions which are reported per 0.1 mL. Each product has a specific recommended population assay method. Population procedures are located on each product page.
Geobacillus stearothermophilus, which is contained in Mesa Labs liquid ampoule biological indicators (MagnaAmp, SterilAmp II, ProSpore), has a growth range of approximately 40 – 70ᵒC and therefore cannot grow at room temperature. If the ampoules are still purple and have not turned yellow, they should be ok. If the ampoules have experienced temperatures higher than 40ᵒC, the spores would begin to germinate and lose their heat resistance.
The typical spore forming organism used to monitor steam sterilization cycles is Geobacillus stearothermophilus. This Bacillus, however, may be too resistant to use in low temperature sterilization. BIs manufactured with Bacillus subtilis “5230” are acceptable but you will want to have data available to demonstrate that the reduced resistance capabilities of the Bacillus subtilis “5230” still represents an adequate challenge to your sterilization process when compared to the resistance capabilities of the product bioburden. For example, if your product bioburden is capable of “out-surviving” the spores in the BI, the particular BI in question is not appropriate. In such cases, one will need to perform bioburden testing to identify and document the resistance capabilities of the product bioburden and compare the results to the BI resistance. For additional information, please read Spore News Volume 1, Number 2 and Spore News Volume 1, Number 3 at the following links.
Bacillus subtilis “5230” is a spore forming Bacillus that has a lower resistance to steam than Geobacillus stearothermophilus. Use of this organism is recognized in ISO 11138-3:2017. Mesa manufactures Strips, liquid ampoules (SterilAmp II 5230) and Suspensions using this organism for customers that have heat sensitive products.
BIs manufactured with Bacillus subtilis “5230” are acceptable but you will want to have data available to demonstrate that the reduced resistance capabilities of the Bacillus subtilis “5230” still represents an adequate challenge to your sterilization process when compared to the resistance capabilities of the product bioburden. For example, if your product bioburden is capable of “out-surviving” the spores in the BI, the particular BI in question is not appropriate. In such cases, one will need to perform bioburden testing to identify and document the resistance capabilities of the product bioburden and compare the results to the BI resistance. For additional information, please read Spore News, Volume 1, Number 2 and Spore News Volume 1, Number 3 at the following links.
The EZTest Steam biological indicator is perfectly suited for applications such as these. We also have an array of specially manufactured gaskets which will securely hold the BI in place.
Mesa has several solutions to assist you with biological indicator placement during sterilization in place (SIP) validation.
The MeCo line of validation tools is designed to provide consistency between validation cycles by enabling controlled placement of a biological indicator along with the thermocouple. These devices can be used with spore strips and have different sizes and configurations for use in piping and on flat surfaces. For additional information about this solution, please read Spore News Vol 14, No 2.
The EZTest Steam biological indicator is also perfectly suited for applications such as these. We offer an array of specially manufactured gaskets which will securely hold the BI in place. For additional information about Sterilization in Place (SIP) validation efforts, please read the following Spore News.
When trying to verify or duplicate someone else’s data, rule number 1 is to eliminate as many potential sources for variation as possible. Essentially, you want to execute the test in as close to an identical manner as was performed to obtain the original data. Population procedures are located on each product page.
For additional information, please read Spore News Volume 4, Number 6 and Spore News Volume 10, Number 2 at the following links.
The spores haven’t changed their resistance capability; rather the test conditions have been altered. To measure D-value, the spores must be placed onto a carrier material. Together, the spores and carrier form a system. If one changes the carrier material used, the system has changed and the measured resistance will also be impacted. For a detailed discussion, please review Spore News Volume 5, Number 1 at the following link.
The bacterial spores used to inoculate Mesa Labs biological indicators are nonpathogenic, naturally occurring soil bacteria that are probably already present in a facility due to being carried in by people via soiled shoes, clothing and general every day human use of the facility. The bacterial spores on the biological indicators are probably in a higher concentration than what would be introduced by people but will not be a problem in a facility that employs Good Lab Practices (GLP) and aseptic handling. For additional information, please read Spore News Volume 4, Number 5: Will BI Spores Contaminate My Production Environment.
Mesa Labs performs D-value testing on EZTest steam at 121ᵒC, 124ᵒC, 127ᵒC, 132ᵒC, 134ᵒC and 135ᵒC. The Certificate of Analysis lists the D-values at 121ᵒC, 132ᵒC, 134ᵒC and 135ᵒC. The z-value listed on the Certificate of Analysis is calculated using the D-values at 121ᵒC, 124ᵒC and 127ᵒC per the ISO 11138-3”2017 requirement of using three D-values between 110ᵒC and 138ᵒC to calculate the z-value.
Mesa Labs performs D-value testing on MesaStrips and Spore Strips for steam at 121ᵒC, 124ᵒC, 127ᵒC, and then extrapolates the D-value at 134ᵒC. The Certificate of Analysis lists the D-value at 121ᵒC and the extrapolated D-value at 134ᵒC. The z-value listed on the Certificate of Analysis is calculated using the D-values at 121ᵒC, 124ᵒC and 127ᵒC per the ISO 11138-3”2017 requirement of using three D-values between 110ᵒC and 138ᵒC to calculate the Z-value.
It is very difficult to pour or pipette all the liquid out of the MagnaAmp ampoule. It is also very difficult to rinse all the spores off the inside glass surface of the ampoule. It is best to place the ampoules in a 250 mL Wheaton jar or other Pyrex jar. Crush the ampoule with a sterile stainless steel rod. This allows the capture of all of the media and allows the washing of the inside of the glass surfaces. Follow the link below to the MagnaAmp population assay instructions.
And for additional information, please read Spore News Volume 10, Number 2 at the following link: Spore News Vol. 10 No. 2: Total Viable Spore Counts
NO. There are three critical variables in a steam sterilization cycle, time, temperature and saturated steam. A liquid BI placed in the chamber will only be monitoring time and temperature and not saturated steam.
As the temperature inside the chamber rises, so will the temperature inside of the liquid BI which in turn will create a steam environment inside of the BI and possibly kill the spores. The spores inside of the BI may be killed but the bioburden on the dry goods may not be killed if there was not saturated steam inside of the sterilizer chamber. Since the liquid BI does not monitor saturated steam, the dead spores may simply create a false sense of security because in reality the dry goods may not be sterile. Saturated steam is about 10 times more lethal than dry heat so the time and temperature may appear sufficient but in reality the cycle is not sufficient if there is not saturated steam.
For example, steam sterilization of porous loads of fabrics or hard goods loads of glass or metal instruments or machine parts are extremely sensitive to the presence of residual air in the autoclave. SterilAmp, MagnaAmp and ProSpore are not sensitive to the presence of residual air in autoclaves. Air will accumulate in the coolest location in the chamber and that is usually in lumens of devices or in the center of porous loads. Sterilization is MUCH slower in a trapped air pocket versus saturated steam. The SterilAmp, MagnaAmp and ProSpore will only respond to temperature. Since they are sealed liquid ampoules they generate their own saturated steam inside to kill the spores. These sealed ampoules placed in air pockets could be killed when spores on paper carriers such as EZTest® or spore strips demonstrate survivors.
For additional information, please read Spore News Volume 12, Number 5 at the following link. Spore News Vol. 12 No. 5: Biological Indicator Selection
Mesa Labs cannot know the requirements of every regulatory agency around the world, so it may be worth checking with your regulating body to see if they have any specifications or recommendations concerning the frequency of BI use. However, if a BI is not used to evaluate cycle performance, the load is being released based only on the physical data available about the cycle, i.e. parametric release. In a properly validated sterilization process the expectation is that the BIs will be killed but if a BI is not used in every load, an assumption is being made that biological kill was achieved. Relying on assumptions puts one at risk of releasing a load that would have been quarantined had the BI been used and it detected conditions that probes can miss. At Mesa Labs, we tell customers that BIs are your insurance to sterility assurance.
Process Challenge Devices (PCDs) are used in routine production sterilization cycles as an external test pack. They are designed to help medical device manufacturers and contract sterilization providers efficiently and accurately confirm EO sterility assurance. PCD patented products nominally consist of any commercial Biological Indicator strip, disc or Self-Contained BI (SCBI) in a proprietary EO barrier pouch. Directions for use can be found here.
Laboratory testing of our various PCD ‘types’ (particular polymeric film/pouch specifications) is done using the Stumbo-Murphy-Cochran (SMC) fractional method in a Biological Indicator Evaluator Resistometer (BIER) vessel. The values listed are nominal and should be used for reference and comparison only. Actual D values vary dependent upon the type of BI and other inherent process variabilities. Please review our PCD Selection Guide or contact usfor further information.
Based on real-time studies conducted, the shelf life of BIs in our PCD packaging is equal to, or greater than, the BI manufacturer’s published expiration date.