Objectives: Dental instrument sterilization with steam autoclaves is critical to
maintaining infection control standards in dental practice, and preventing patient-to-patient
transmission of pathogenic bacteria and viruses. The American Dental
Association and the United States Centers for Disease Control and Prevention
recommend, and many state dental laws require, weekly use of biological spore tests to
verify dental instrument sterilization outcomes. However, the most widely used
biological spore test needs microbial culture incubation for 2 days after autoclave
exposure, which limits swift identification of sterilization failure.
To address this issue, this study evaluated the reliability of a new rapid biological
spore test for determining the sterilization efficacy of dental steam autoclaves within 20
minutes.
Methods: Two commercial biological spore tests were evaluated in Temple
University dental school steam autoclaves, 1.) the Steris Celerity 20 Steam Biologic
Indicator with a 20-minute outcome time requirement, and 2.) the 3M Attest 1262
Biological Indicator with a 48-hour outcome time requirement. Both biological spore
tests employed live thermoresistant Geobacillus stearothermophilus spores as an
indicator of whether sterilization conditions in steam autoclaves were met or not. To
compare their efficacy, a total of 157 pairs of the two biological spore tests were placed
into dental steam autoclaves with dental instrument cassettes, and subjected to
manufacturer-recommended steam autoclave temperature and air pressure operating
conditions for an adequate sterilization time of 15 minutes. Two additional groups of 10
pairs each of the two biological indicators were subjected to appropriate steam autoclave
temperature and air pressure settings, but only for aborted non-sterilizing time periods of
10 and 5 minutes, respectively. Subsequent aseptic processing and laboratory incubation
of both biological indicators was initiated within 2-24 hours, and followed manufacturer
recommendations.
After autoclave exposure, Steris Celerity 20 Steam Biologic Indicator test
ampoules were incubated in a specialized instrument for 20 minutes at 57 °C, which also
spectrophotometrically evaluated the microbial culture medium for fluorescent α-
glucosidase enzyme signal changes. No change in fluorescent intensity represented
successful sterilization, whereas increased fluorescence indicated survival of viable G.
stearothermophilus spores germinating into vegetative bacterial cells after failed
sterilization.
3M Attest 1262 Biological Indicator ampoules were incubated for 48 hours in a
laboratory heating block at 57 °C, after which a pH-based color change in the microbial
culture broth was visually assessed. No change in the color of the culture broth (purple
color remains) indicated successful sterilization, whereas development of a yellow color
in the culture broth, as a result of viable G. stearothermophilus spore germination into
vegetative bacterial cells, denoted failed sterilization.
Results: A total of 354 biological indicators were exposed to dental steam
autoclaves sterilization cycles, incubated for either 20 minutes or 48 hours, and evaluated
for G. stearothermophilus spore growth. The Steris Celerity and 3M Attest biological
spore tests both uniformly detected successful sterilization, with no G. stearothermophilus
spore growth, after 15 minutes of steam autoclave exposure at manufacturer recommended
steam autoclave temperature and air pressure operating conditions. This
provided 100% agreement, and no statistically significant difference in the prevalence of
successful sterilization outcomes, between 157 pairs of both biological indicator types
after 15 minutes of steam autoclave exposure.
Similarly, both biological spore test systems were also in complete agreement
after only 5 minutes of steam autoclave exposure, with 100% of both biological
indicators positive for G. stearothermophilus spore growth, indicating failed sterilization.
In contrast, after 10 minutes of steam autoclave exposure, there was a complete
lack of agreement between the two types of biological indicators. All 10 Steris Celerity
spore tests were positive, whereas all 10 3M Attest ampoules were negative, for G.
stearothermophilus spore growth after 10 minutes of steam autoclave exposure. Relative
to this disagreement, a non-biological chemical indicator strip that was part of the Steris
biological indicator test system failed to have a darkened bar develop and extend into the
“Accept (OK)” portion of the strip for all Steris Celerity spore tests exposed to either 5
minutes or 10 minutes of steam autoclave exposure, indicating that adequate autoclave
steam, temperature and/or time parameters had not been attained for sterilization.
Conclusions: The Steris Celerity biological spore test was successful in rapidly
determining the sterilization efficacy of dental steam autoclaves within only a 20-minute
incubation time period, as compared to 48 hours of incubation required by the widely-used
3M Attest biological spore test. As a result, this rapid assay offers earlier detection
of steam autoclave sterilization failure before potentially contaminated dental instruments
are used in clinical patient care.
The alarming failure of 3M Attest biological spores to grow after a non-sterilizing
10-minute steam autoclave exposure time warrants further product evaluation. / Oral Biology
| Identifer | oai:union.ndltd.org:TEMPLE/oai:scholarshare.temple.edu:20.500.12613/6549 |
| Date | January 2021 |
| Creators | Lee, Andie Hyunkyung |
| Contributors | Rams, Thomas E., Page, Lawrence, Whitaker, Eugene J. |
| Publisher | Temple University. Libraries |
| Source Sets | Temple University |
| Language | English |
| Detected Language | English |
| Type | Thesis/Dissertation, Text |
| Format | 31 pages |
| Rights | IN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available., http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | http://dx.doi.org/10.34944/dspace/6531, Theses and Dissertations |
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