Spore Suspensions
Spore Suspensions are diluted aliquots from our primary spore crop (batch). They are used to directly inoculate (and therefore challenge) a material or solution with a known concentration of spores. US FDA requires medical device and pharmaceutical manufacturers to challenge their products directly with spores prior to approving them for sale. This challenge is intended to determine if the device's carrier material or pharmaceutical's properties (viscosity, salt content, etc.) has any sporicidal or preservative effect that will impact the manufacturer's ability to sterilize the product and to determine instructions on how the user can sterilize the device if reusable.
Suspensions offered in a 40% ethanol solution or 100% deionized H2O.
Some hydrophobic materials would cause a drop (0.1ml) to bead on its surface. As this bead dries, the spores would be clumped on top of each other. For these types of materials it would be to your advantage to use the ethanol solution so the spores spread more evenly over the surface. The same is also true when inoculating into a solution, where a water inoculum may not be miscible.
Species
Mesa manufactures many species of non-pathogenic spore-forming bacteria. Most are used for various types of sterilization, though some have other uses. Following is a brief description of the most common uses:
G. stearothermophilus1 (reference # 7953) for steam, B. atrophaeus1 (reference # 9372) for dry heat and EO and B. pumilus1 (reference # 27142) for gamma irradiation are standard products.
B. subtilis1 (reference # 6633) – Used to test the growth promotion ability of bacteriological media (specified in USP and other compendial monographs). We do not certify this organism with any resistance characteristics.
B. subtilis1 (called “Designate 5230”) is used in steam sterilization procedures below 121° C. Some pharmaceutical products are sterilized at 106° to 115° C for longer times because they are heat labile and would be damaged at 121°C or higher temperatures. This species has been used as a challenge to the lower temperatures in steam, where G. stearothermophilus would be too great a challenge. In using a lesser challenge (C. sporogenes species and environmental isolates are also used) it is necessary to have an extremely high level of control over the manufacturing process, environment, and bioburden of components. This organism is certified with a Steam D and z-value so its resistance at the lower temperatures can be determined.
G. stearothermophilus1 (reference # 12980) is widely used in the validation of Hydrogen Peroxide (H2O2) vapor sterilization of barrier isolators and clean areas in pharmaceutical production. This species is typically inoculated onto steel carriers so it is compatible with the H2O2 process and similar in material to items typically found in these production areas. This organism is certified with an H2O2 D-value.
G. stearothermophilus1 (reference # 10149) is used to detect residual antibiotics in dairy products. This organism is not certified for any resistance characteristics.
B. thuringiensis1 (reference # 29730) – This species has a protein crystal on the spore coat that makes the spores toxic to various insect larvae. In some areas, trees are sprayed with a spore suspension to protect them from certain larvae. Geneticists have engineered this protein to be expressed in some varieties of corn (referred to as Bt-corn). B. thuringiensis has also been used as a surrogate to B. anthracis or other more hazardous organisms in testing decontamination processes. We do not certify this organism with any resistance characteristics.
B. cereus and B. megaterium would be used in a similar manner to B. subtilis designate 5230 (lower temperature steam sterilization at 106° to 115°C). B. cereus is also used as a surrogate for B. anthracis and other more dangerous organisms in testing decontamination processes. We do not certify this organism with any resistance characteristics, but one can be provided upon request for a fee.
Related Information
Note:
1 Derived from recognized reference strains as specified within USP, ISO or EN guidelines. These products are not certified as being representative of the reference strain and they should therefore not be used where a reference culture is specified.