General
When biological indicators are purchased from a commercial source, their suitability for use in a specific sterilization process should be established through developmental sterilization studies unless existing data are available to support their use in the process.Evaluation of the biological indicator must be performed at the time of each validation exercise or with a new lot number or with a change in vendor/manufacturer of biological indicators. The user should establish in-house acceptance standards for biological indicator lots and consider rejection in the event the biological indicator lot does not meet the established in-house performance standards.
Upon initial receipt of the biological indicator from a commercial supplier, the user should verify the morphology of the purchased biological indicator microorganism. A microbial count to determine the mean count per biological indicator unit should be conducted.
Purity
By examination of the spores on a suitable plate culture medium, there should be no evidence of contamination with other microorganisms that will adversely affect the performance of the indicator organism.Resistance performance tests
Proceed as given in IS. Resistance Performance Tests.Medium Suitability in Self·contained Biological Indicators
Sterility
Incubate 10 self-contained biological indicator systems at the optimal recovery temperature specified by the manufacturer for 48 hours, making sure that there is no contact between the individual inoculated spore paper carrier and the supplied growth medium. Examine the incubated medium visually (for change in color indicator or turbidity) and microscopically (for the absence of microbial growth).Growth promotion of medium prior to sterilization treatment
Submerge 10 self-contained units in a water bath maintained at 95° to 100° for 15 minutes. Cool rapidly in an ice water-bath at 0° to 4°. Remove the units from the ice water bath, immerse the paper carrier in the self-contained medium and incubate at the optimal temperature specified by the manufacturer. Examine visually after 48 hours. All the specimens under test show growth. If one or more specimens do not show growth, repeat the test with 20 additional units.Ability of medium to support growth after exposure to the Sterilization conditions
Take 10 units after they have been exposed for a kill time as stated in the Certificate of Analysis. Aseptically remove and pool the medium from each unit. Prepare a suspension of the indicator microorganism as directed for Total Viable Spore Count. Prepare a dilution of that suspension and inoculate the pooled medium with enough suspension to contain a total of 100 to 1000 microorganisms in a 10 ml aliquot obtained from the pooled volume. Incubate the inoculated pooled medium at the optimal temperature specified by the manufacturer. Clear evidence of growth is obtained within 7 days.Also see: New Genetically Engineered Biological Indicators
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