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9: Biological Testing of Your Sterilization Process |
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By - Pauline W. Fallis,
With all we do for infection control, one of the important aspects is
monitoring your sterilization process. There are three types of monitors
that you use. Mechanical indicators that are the gauges and other
mechanical devices that are on your sterilizer. Chemical indicators that
use a chemical change to indicate that the parameters of time and
temperature have been reached. And biological indicators (BI) or spore
strips that verify that the microorganisms have really been killed.
Biological indicators use live bacterial spores to measure the ability of
the sterilization cycle to actually kill bacteria. Biological testing
products are impregnated with the microorganism Bacillus stearothermophilus
spores. They are the organism that challenges your sterilizer, as they are
more resistant and in numbers far greater then your sterilizer will most
likely encounter. If this spore is killed then most anything can be
killed.
The frequency of using biological indicators is according to your usage of
the sterilizer. The AAMI standard indicates that the sterlizer should be
tested at least weekly. Routine testing is mandatory.
There are two types of biological testing products available. The first is
the spore strip that are strips of paper impregnated with Bacillus
stearothermophilus spores that must be sent to a testing facility for
testing which takes considerable time before you get a result. The second
is an ampoule which holds a broth containing the Bacillus
stearothermophilus spores. These you incubate yourself and have the result
within 48 hours.
If you choose to use a biological indicator that you incubate yourself be
aware that Bacillus stearothermophilus does not incubate at the
temperatures found in the standard laboratory incubator. Special
biological indicator incubators are available from the manufacturer of the
BI. Remember to incubate an unsterilized BI as a control at the same time.
If the microorganism in the BI does not grow after incubation then the
sterilization process has been successful.
What do you do if you have a positive result
A positive result is when the Bacillus stearothermophilus grows during
incubation. If the test is positive the following actions must be taken:
1. All items that were sterilized since the last negative test are
considered unsterile.
2. Retrieve all suspected items to be reprocessed.
3. Compile a written record of your activities. This report should include
the time and date of the failed sterilization cycle, a description of the
sterilizer, the load number (if you lot number your loads), any results
from a chemical indicator and if your sterilizer has mechanical monitoring
devices that information also. The information about what you did about
the failure should also be included.
4. If it is determined that the sterilizer malfunctioned, it should be
repaired and a negative result from a biological test must be obtained
before it is used again.
Testing with a biological indicator
Biological indicators are placed in the centre of the chamber, basket or
cassette. Run your normal sterilization cycle using a full sterilizer
load. When the cycle is completed remove the indicator from the
sterilizer. Test according the BI manufacturer's instructions (send out
for testing or incubate yourself).
The absence of microbial growth is a clear indication that the sterilizer
operated efficiently. This is the only way that you can be assured that
the process of sterilization is successful and that the items sterilized
are safe for use on your clients. Client safety is your prime concern.
References
AAMI Steam Sterilization and Sterility Assurance in Office Based,
Ambulatory Care, Medical and Dental Facilities. Association for the
Advancement of Medical Instrumentation, Arlington VA, 1992
Doruette, W.H.L. ed The Central Service Technical Manual, International
Association of Hospital Central Service Management, Chicago, Illinois 1981
Fallis, P.W., Handbook of Infection Control in Office based Health Care
and Allied Services, Canadian Standards Association, PLUS112, Toronto, 1994
INFECTION CONTROL ARTICLES
- PREPARING FOR THE PATIENT/CLIENT
Spring 2001, Volume 8, Number 1
- PREVENTING INFECTION FOR ELECTROLYSIS
Fall 2000, Volume 7, Number 2
- INFLUENZA
Spring 2000, Volume 7, Number 1
- MICROORGANISMS AND INFECTIOUS DISEASE
Summer 1999, Volume 6, Number 2
- BLOOD BORNE INFECTIOUS DISEASES AND PERSONAL PROTECTION
Spring 1999, Volume 6, Number 1
- MICROORGANISMS & INFECTION
Fall 1998, Volume 5, Number 2.
- BIOLOGICAL TESTING OF YOUR STERILIZATION PROCESS
Spring 1998, Volume 5, Number 1
- STEAM STERILIZATION
Fall 1997, Volume 4, Number 2
- CHEMICAL STERILIZATION
Spring 1997, Volume 4, Number1
- DRY HEAT STERILIZATION
Fall 1996, Volume 3, Number 2
- STERILIZATION
Spring 1996, Volume 3, Number 1
- IS YOUR USE OF NEEDLES SAFE IN YOUR PRACTICE?
Fall 1995, Volume 2, Number 2
- PREPARING INSTRUMENTS FOR STERILIZATION
Spring 1995, Volume 2, Number 1
- WHY ARE GLASS BEAD STERILIZERS NOT RECOMMENDED FOR USE IN ELECTROLOGY?
Fall 1994, Volume 1, Number 2
- STERILIZATION: HOW, WHEN, AND WHAT WITH
Spring 1994, Volume 1, Number1
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