Biological Indicator for Steam Sterilization, Paper Carrier

» Biological Indicator for Steam Sterilization, Paper Carrier, is a defined preparation of viable spores made from a culture derived from a specified strain of Bacillus stearothermophilus, on a suitable grade of paper carrier, individually packaged in a suitable container readily penetrable by steam, and characterized for predictable resistance to steam sterilization. The packaged Biological Indicator for Steam Sterilization, Paper Carrier, has a particular labeled spore count per carrier of not less than 104 and not more than 109 spores. When labeled for and subjected to steam sterilization conditions at a particular temperature, it has a survival time and kill time appropriate to the labeled spore count and to the decimal reduction value (D value, in minutes) of the preparation, specified by:

Survival time (in minutes) = not less than (labeled D value) × (log labeled spore count per carrier

2); and

Kill time (in minutes) = not more than (labeled D value) × (log labeled spore count per carrier + 4).

Packaging and storage— Preserve in the original package under the conditions recommended on the label, and protect it from light, toxic substances, excessive heat, and moisture. The packaging and 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 less than 18 months from the date of manufacture, the date of manufacture being the date on which the first determination of the total viable spore count was made.

Labeling— Label it to state that it is a Biological Indicator for Steam Sterilization, Paper Carrier; to indicate its D value, the method used to determine such D value, i.e., by spore count or fraction negative procedure after graded exposures to the sterilization conditions; the survival time and kill time under specified sterilization conditions stated on the label; its particular total viable spore count with a statement that such count has been determined after preliminary heat treatment; and its recommended storage conditions. State in the labeling the size of the paper carrier, the strain and ATCC number from which the spores were derived, and instructions for spore recovery and for safe disposal of the indicator. Indicate in the labeling that the stated D value is reproducible only under the exact conditions under which it was determined, that the user would not necessarily obtain the same result and that the user should determine the suitability of the biological indicator for the particular use.

Identification— The biological indicator organism complies substantially with the morphological, cultural, and biochemical characteristics of the strain of Bacillus stearothermophilus, ATCC No. 7953 or 12980, whichever is stated in the labeling: under microscopic examination it consists of Gram-positive rods with oval endospores in subterminally swollen cells; when incubated in nutrient broth for 17 hours and used to inoculate appropriate solid media, growth occurs when the inoculated media are incubated aerobically for 24 hours at 55

to 60

, and similar inoculated media incubated concomitantly at 30

to 35

show no evidence of growth in the same period. When examined under conventional biochemical tests for microbial characterization, it shows a delayed weak positive catalase reaction, it does not utilize citrate, propionate or hippurate, it reduces nitrate, but it does not liquefy gelatin, and it gives a negative result with the Voges-Proskauer test. Organisms derived from ATCC strain No. 7953 show negative egg yolk and starch hydrolysis reactions, while those derived from ATCC strain No. 12980 show positive reactions in both tests.

Resistance performance tests—

D value— Proceed as directed for the relevant procedure for D Value under Biological Indicators—Resistance Performance Tests

. The requirements of the test are met if the determined D value is within 20% of the labeled D value for the selected sterilizing temperature, and if the confidence limits of the estimate are within 10% of the determined D value.

Survival time and kill time— Follow the procedure for Survival Time and Kill Time in the section Steam Sterilization, Paper Carrier, under Biological Indicators—Resistance Performance Tests

. The requirements of the test are met if all of the specimens subjected to the steam sterilization for the survival time show evidence of growth, while none of the specimens subjected to the steam sterilization for the kill time shows growth. If for either the survival time test or the kill time test, not more than 1 specimen out of both groups fails the survival requirement or the kill requirement (whichever is applicable), continue the corresponding test with 4 additional groups, each consisting of 20 specimens, according to the procedure described. If all of the additional specimens subjected to steam sterilization either meet the survival requirement for the survival time test or meet the kill requirement for the kill time test, whichever is applicable, the requirements of the test are met.

Total viable spore count— Proceed as directed for Total Viable Spore Count in the section Steam Sterilization, Paper Carrier, under Biological Indicators—Resistance Performance Tests

. The requirements of the tests 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.

Purity—

Presence of contamination by other microorganisms— By examination of the spores on a suitable plate culture medium, there is no evidence of contamination with other microorganisms.

Disposal— Prior to destruction or discard, sterilize it by steam at 121

for not less than 30 minutes, or by not less than an equivalent method recommended by the manufacturer. This includes a test strip employed in any test procedures for the strips themselves.

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

Topic/Question	Contact	Expert Committee
Monograph	Radhakrishna S Tirumalai, Ph.D. Senior Scientist 1-301-816-8339	(MSA05) Microbiology and Sterility Assurance

USP32–NF27 Page 1678