What Causes An Autoclave To Fail A Spore Test?

From The Doctor – to the Technicians – to the Patients: Everyone is at risk if the instruments & hand pieces used in your practice are not sterilized properly. It’s also the law. To protect everyone, the mandated spore test is a way to ensure that your autoclave is functioning properly and is achieving the desired level of sterilization. HOW IS STERILIZATION CONFIRMED?


After a spore strip is processed in a sterilizer, it is mailed to a monitoring service. In a laboratory setting, the spore strip is aseptically removed from its protective envelope and placed in a tube of culture media. It is then incubated for 7 days. For each of the 7 days, the tube of culture media is inspected for cloudiness.



If the spores are live and have not been killed, cloudiness is noted in the culture media. If no cloudiness is noted in the culture media, then sterilization is confirmed.


The most common reason for the test to fail is not due to mechanical failure, but is actually due to operator error. If your autoclave has failed the spore test, this is a good time to review your sterilization procedures with your staff. Observe the technician who is responsible for sterilizing the hand pieces and/or instruments and look for the following problem areas:


  • Is the autoclave being overloaded? Refer to the manufacturers specifications and make sure the technician is not putting in too many items at one time.
  • Is the right temperature being achieved and maintained? Inadequate Temperature: Set the temperature control knob so that it reaches and maintains 270-degrees. Check on it periodically during the cycle to make sure this temperature is not fluctuating more than a couple of degrees.
  • Is the right amount of pressure being reached and maintained? Inadequate Pressure: The chamber pressure should be maintaining approximately 30psi (or manufacturer specifications).
  • Is the cycle being allowed to run for the right amount of time? Inadequate Time: The normal processing cycle varies somewhat by the autoclave manufacturer. Follow the manufactures guidelines. Shortening the cycle endangers everyone, so don’t.
  • Improper packaging of instruments (follow manufacturers recommendations)


If any of the above shortcuts are being taken because the autoclave cannot keep up with your demand, it is time to either increase your inventory of handpieces and/or instruments, or to get an autoclave that processes them faster A question I am frequently asked is If the Chemical Monitoring is Sufficient.. crcst certification



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