Biological Indicators for Moist Heat, Dry Heat, and Gaseous Modes of Sterilization, Nonpaper Carriers
» Biological indicators for moist heat, dry heat, and gaseous modes of sterilization may be nonpaper carriers inoculated with a culture of viable spores derived from one of several sterilization-resistant microorganisms, based on the intended sterilization use. Cultures used for inoculation of carriers include, among others, Clostridium sporogenes, Geobacillus stearothermophilus (formerly B. stearothermophilus), Bacillus atrophaeus (formerly B. subtilis), or Bacillus coagulans. The carriers should be individually packaged for use either within the package or for use upon removal from the package as an unpackaged biological indicator. The packaged biological indicator on the carrier has a particular labeled spore count of not less than 103 and not more than 109 spores per carrier. It has a survival time and kill time appropriate to the labeled spore count and to the decimal reduction value (D value, in minutes), specified by:
Survival time (in minutes) = not less than (labeled D value) × (log of labeled spore count per carrier – 2), and
Kill time (in minutes) = not more than (labeled D value) × ( log of labeled spore count per carrier + 4).
Packaging and storage— Preserve in the original package under the conditions recommended on the label, and protect the package from light, toxic substances, excessive heat, and high relative humidity or moisture. The packaging or container materials do not adversely affect the performance of the article used as directed in the labeling.
Expiration date— The expiration date is determined on the basis of stability studies and is not more than 18 months from the date of manufacture. The date of manufacture is the date on which the first determination of the total viable count was made.
Labeling— Label the package or package insert to state that it is a biological indicator prepared on a carrier for use in label-specified applications for moist heat, dry heat, and/or gaseous sterilization. State the biological indicator D value obtained under defined exposures to stated sterilization conditions using the Survival Curve method, Spearman-Karber method, or Stumbo-Murphy-Cochran method of D value analysis. State the survival time and kill time for the biological indicator carrier under specified conditions on the label. The total viable spore count per carrier following heat shock treatment must also appear on the label or package insert. State in the labeling the strain and ATCC number of the spore suspension used to inoculate the carriers and instructions for spore recovery and for safe disposal of the carriers. Indicate in the labeling that the stated D value is reproducible only under the exact conditions determined by the manufacturer and that the user would not necessarily obtain the same results if different exposure conditions were used. State that the user should determine the suitability of the carrier biological indicator for the user's particular purpose and exposure conditions.
Identification— Identification for the biological indicator is of less importance than the more relevant concerns of population and resistance to the sterilization processes. The manufacturer should identify the species used.
D value— Proceed as directed in the relevant procedure for D Value Determination under Biological Indicators—Resistance Performance Tests 55. The requirements of the test are met if the determined D value is within 20% of the labeled D value for the selected sterilizing conditions, and if the confidence limits of the estimate are within 10% of the determined D value. The D-value determination method used should be that identified by the biological indicator manufacturer.
Survival time and kill time— Follow the procedure in the subsection Survival Time and Kill Time in the section D-Value Determination under the chapter Biological Indicators—Resistance Performance Tests 55. The requirements of the test are met if all of the carriers subjected to sterilization exposure conditions intended to indicate survival show evidence of growth among the exposed carriers, while none of the carriers subjected to conditions designed to induce total kill show growth. If for either the survival test or the kill time test, not more than one carrier out of both groups fails the survival or kill requirements, continue the corresponding test with four additional groups, each consisting of 10 carriers, according to the procedure described. If all of the additional specimens subjected to the specific sterilization process either meet the survival requirements for the survival test time or meet the kill requirement for the kill test, whichever is applicable, the requirements are met.
Total viable spore count— Proceed as directed in the subsection Biological Indicators for Moist Heat, Dry Heat, and Gaseous Modes of Sterilization, Nonpaper Carriers in the section Total Viable Spore Count under the chapter Biological Indicators—Resistance Performance Tests 55. The requirements of the test are met if the average number of viable spores per carrier are within 50% and +300% of the labeled count per carrier or within a lesser range that may be stated by the manufacturer.
Purity— There is no evidence of contamination with other microorganisms following examination of spores recovered from the carriers using a suitable plate culture medium.
Disposal— Prior to destruction or discarding the carriers, sterilize by moist heat sterilization to ensure that the carrier surface is exposed to 121 for not less than 30 minutes, or by an equivalent method recommended by the manufacturer.
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Topic/Question Contact Expert Committee
Monograph Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
(MSA05) Microbiology and Sterility Assurance
USP32–NF27 Page 1677
Pharmacopeial Forum: Volume No. 30(1) Page 63