Q & 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?
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.