The Importance of the Sterilizer Monitoring Process

Typically sterilizer monitoring is accomplished through a combination of mechanical, chemical, and biological procedures formulated to evaluate sterilizing conditions and procedural effectiveness.

1.  Mechanical sterilization monitoring techniques include assessing cycle time, temperature, and pressure of sterilization equipment.  Correct readings do not ensure sterilization but incorrect readings are often a first indication of a problem within the sterilization process.

2. Chemical indicators, both internal and external, use chemicals to assess physical properties like temperature, during the sterilization process.  Internal chemical indicators are placed in every sterilization package to ensure that the sterilization agent has penetrated packaging material and reached the instruments inside.  If the internal indicator cannot be seen from outside the package then an external indicator needs to be used.  

Single-parameter internal indicators monitor only one sterilization parameter and are available for steam, dry heat, and unsaturated chemical vapor.  Multi-parameter internal indicators measure two to three parameters providing a more reliable indication that sterilization conditions have been met.  Multi-parameter internal indicators are only available for steam sterilizers like autoclaves. 

Chemical indicators do not prove that sterilization has been successful hence a biological indicator, specifically a spore test, is required. 

3.  Biological (BIs) indicators are the most accepted means of sterilizer monitoring because the biological process directly determines whether the most resistant micro-organisms are present.  BIs are the most accurate means of ensuring that the sterilization pre-conditions necessary for sterilization have been met.  The spores used in BIs are more resistant and more numerous than common microbial contaminants found on patient care equipment.  Thus an inactivated BI indicates that all pathogens and potential pathogens in the load have been killed.

Regardless of the sterilization method, it is important that the process follow the device manufacture’ instructions.  These instructions should be referenced each time the device is sterilized.  

How Often Should I Perform Sterilizer Monitoring?

According to the Centers for Disease Control and Prevention (CDC),sterilization procedures should be monitored through a combination of mechanical, chemical, and biological techniques designed to evaluate the sterilizing conditions and the procedure's effectiveness.

The most common testing procedures include:

1)    leak rate test,

2)    bowie Dick type air removal test,

3)    chemical indicators, biological indicators,

4)    process challenge devices,

5)    physical tests.

Mechanical techniques for monitoring sterilization include assessing the cycle time, temperature, and pressure of sterilization equipment by observing the gauges or displays on the sterilizer.

Chemical indicators, internal and external, use sensitive chemicals to assess physical conditions.  Because chemical indicators do not prove sterilization has been achieved, a biological indicator like a spore test is required.

Biological indicators (BIs) are the most accepted means of monitoring the sterilization process because they directly determine whether the most resistant microorganisms like the Geobacillus or Bacillus species, are present. Chemical and mechanical indicators merely determine whether the physical and chemical conditions necessary for sterilization have been met.

Biological monitoring (BI), spore testing, should be done on a weekly basis, to verify the correct functioning of sterilization cycles. Weekly testing is the minimum and more frequent testing may be required.  Follow manufacturing directions with respect to correct placement of the BI in the sterilizer.  When monitoring, a control BI not processed through the sterilizer but from the same lot as the test indicator, should be incubated with the test BI. The control should yield positive results for bacterial growth.

In addition to routine biological monitoring, additional testing is necessary and should be conducted after:

1)    a new type of packaging material or tray is used,

2)    training new sterilization personnel,

3)    a sterilizer has been repaired,

4)    changes in the sterilizer loading procedures.

Ultimately, monitoring frequency is the responsibility of the user, but should follow manufacturing guidelines.