Biological monitoring of sterilizer function depends on the sterilizer killing the test organism.  Because bacterial spores are the most resistant form of bacteria, spores have been the most common test material.  The test strips supplied by the Sterilizer Monitoring Service are imbedded with spores of two species of bacteria; Geobacillus stearothermophis and Bacillus atrophaeus.  Why use two species? Bacillus atrophaeus spores are notoriously resistant to heat, making them perfect for testing heat only sterilizers like ovens.  Geobacillus stearothermophis is a thermophilic bacteria, original isolates in the thermal pools of Yellowstone.  They are cultured at 55 C°, too hot for almost every other bacterial species.  This reduces the chance of a false positive result to essentially zero.  G. stearothermophis is the test species for steam and chemical sterilizer units.

Your records are stored in an encrypted data base on site.  If you need a copy of your record for a specific period, just call us but your email record of results is satisfactory for verification of compliance.  In December, you will receive a hard copy of the past years record, along with your certificate of participation in the monitoring service. 

All states require verification of sterilizer function

Most states require weekly monitoring; a few still allow monthly tests.  Check with your local Board of Dentistry for the standard of practice in your area.  Oregon, Washington and California require weekly tests.  Medical offices are required to test monthly. In Oregon, business doing electrolysis, or tattooing and piercing are also required to monitor sterilizer function on a monthly basis.

For almost 40 years, the Sterilizer Monitoring Service at the Oregon Health Sciences University (SMS) has been a source of third-party biological monitoring for dental, medical and other offices.  Dental and medical offices are required by statute to verify the sterilizers used meet current standards.  In Oregon, weekly sterilizer monitoring is required for dental offices (see Section 818-012-0040).  Medical offices are required to monitor sterilization equipment monthly.

New clients should register with us by phone at  503-494-4641. You will be asked to provide information about your office and the type and number of sterilizers you use. Each sterilizer is assigned a unique identifying number in our database. You will receive packets of test strips and sheets of barcodes for each sterilizer. Simply add the test strip to a load and sterilize as usual. Place the barcode on the sterilized test strip and mail it to us. That’s it!  Once you are a registered client, all you have to do to get more test strips is send us a test strip order form  by mail or fax and we will send you a new supply.

Because of the special culture process developed by the SMS, we will have your results within 24 hours of the strip getting to us.  You will receive an email with the test results.  If the test is not sterile, you will also get a phone call from us to ensure the most rapid retesting possible.

Q and A

Q: Is biological monitoring (spore test strips) acceptable for all methods of sterilization?
A:  Steam, chemical and oven sterilization can all be verified by the dual species test strips used by the  SMS at OHSU.  Steam and chemical sterilization is verified by the spores of Geobacillus stearothermophis, cultured at 55 C°.  Oven sterilization is verified by spores of Bacillus atrophaeus, cultured at 37 C°.  The spores of both species are found on the test strips used by SMS.  One type of test strips for all sterilizers.

Q:  Isn’t the indicator tape sufficient to show sterilization?
A:  No.  Autoclave tape only shows heat, not pressure and certainly not chemical sterilization reagents.  It isn’t even that good for heat.  Exposure to sunlight will cause the tape to turn.  

Q:  Are steam sterilizers better than chemical sterilizers?
A: Both steam and chemical sterilizers are effective and efficient.  The difference is that chemical sterilizers are more sensitive to over crowding of the chamber.  Steam uses head and pressure so distribution within the chamber is not as important as it is with chemical sterilizers.

Q: How do I order test strips?
A: If you are a new client, call us at 503-494-4641. You will need to provide us with information about what kind of sterilizers you have and how many. To order more test strips, fill out a client order form and send it to us by FAX or mail. Payment can be made by check made out to OHSU Sterilizer Monitoring Service and mailed to our address, or we can bill you through OHSU's billing office if you prefer.

Sterilizer Monitoring Service
OHSU School of Dentistry
SD-SMS 2730 SW Moody Ave.
Portland, Ore., 97201-5042

Q: What are control strips?
A: Control strips are not like the controls you might have used in an experimental setting somewhere along the line. Control strips act as a positive control for the test strips.  They are not run through the sterilizer and show that the spore germination process is working correctly on our end of the process.  Control strips are not mandated by the state. That leaves it to us to determine when to use a control strip. 

Control strips are supposed to control for variation in strip storage conditions in the office. In most office, all the strips are stored together, test and control. A strip is removed from storage, sterilized, barcoded and sent to us.  What a control strip is actually monitoring is the trip from your office to ours.  One envelope with however many test strips needs only one control strip.  If you are storing strips in multiple locations, a control strip in all locations could be used.  The test strips are extremely stable and remain viable for many years.  Accidental inactivation of the spores is practically impossible.  With weekly testing, by the time a not sterile test strip is discovered and reported, the next week's tests are in the works.

Use of control by offices with a large number of sterilizers (four or more by my calculation) address the very small possibility of false negative aggregated by an increased number of simultaneous tests. The probability of a false negative is still vanishingly small, but that's a decision for the one whose license is on the line.

Q: What happens if I miss a testing period?
A: If you don't get a test recorded for a testing period, a week or a month, depending where you are located, the testing record can't be filled in. Even if you did the test but didn't get it sent, don't send it with the next period's test strip. If we get two strips for the same sterilizer at the same time, we will run the strip with the most recent test date. In Oregon (and most other states), weekly testing is the standard of practice and Oregon takes it seriously.

In addition to sterilizer testing, SMS also does water line testing.