What if the sterilizer fails

Biological indicators (BI) are the most valid method for monitoring the sterilization process. Regular use of spore tests helps to support the primary goal of sterilization

By Charles John Palenik

Biological indicators (BI) are the most valid method for monitoring the sterilization process. Regular use of spore tests helps to support the primary goal of sterilization — patient safety through the universal delivery of sterile instruments chairside.

Monitoring evaluates both sterilizer and office personnel performance and the materials that are used. This is especially valuable when new types of packaging are selected or when different loading procedures are employed. Also, spore testing is an essential part of the evaluation of any repaired sterilizer prior to placing it back into use. At least weekly spore testing is recommended.

The desired outcome of biological testing is the killing of the spore challenge. The results of a "negative" test indicate sterilization. Failure to kill the spores (a "positive" test, bacterial growth) is a significant event that requires immediate action. A review of the monitoring process would be useful. The list of questions in the box at right is to be asked of the practice's compliance coordinator and to the practice's monitoring service in the event of a positive spore test.

Some practices use monitoring systems that allow in-house incubation. In such cases, proper processing and interpretation of the results must be carefully completed.

Action plan

If operational (for example, time, temperature, and pressure) and chemical (internal and external) indicators suggest that the sterilizer is functioning properly, then a single spore strip failure likely does not indicate sterilizer malfunction. However, the spore test should be immediately repeated. A second failure indicates the likelihood of a mechanical or procedural problem.

A number of factors may be involved with a sterilization failure. Many are due to some type of human error. Overloading, improper wrapping or packaging, and insufficient exposure times are common operator mistakes. However, all potential causes of sterilization failure — including mechanical breakdown — must be investigated. Following is a list of four steps that are recommended after a spore test failure.

Step One — Take the unit out of service. After receiving the second positive spore test, immediately take the sterilizer out of service until the cause of the problem has been determined and proper changes made. Items processed since the last spore test may not have been sterilized. All unused items need to be collected and processed again in another sterilizer.

Step Two — Review sterilization procedures. All monitoring records, including printouts of operational parameters, chemical indicator results, and spore testing since the last negative BI test should be examined.

The sterilizer's operations manual as well as the practice's written instrument sterilization policies should be reviewed. This would include procedures used by all personnel that recycle instruments. The review should include both candid discussion and direct observation. Confirm that all involved people are aware of and routinely practice the proper procedures and use the correct materials. A review of the practice's BI monitoring process would also be appropriate.

If a review indicates potential areas of concern they should be addressed. However, sometimes the review does not determine an obvious cause of a BI test failure.

Step Three — Retest and observe operational parameters. All repaired or replacement sterilizers must be spore tested before being placed into service. The sterilizer must be operated according to the manufacturer's recommendations. All operational parameters (for example, time, temperature, and pressure) should be observed. It is important that they remain constant throughout the entire cycle. If the color change of the chemical indicators is correct and the BI test reports spore kill, the sterilizer can be used.

Step Four — Determine the fate of the sterilizer. Sometimes sterilizers operated properly continue to fail spore tests. In such cases, the practice should consider the purchase of a new unit.

More information about sterilization monitoring is available from the Organization for Safety & Asepsis Procedures (OSAP) website (www.osap.org/issues/pages/ position/pp-ip.htm).


Monitoring checklist

• Was the proper type of biological indicator (BI) used?
• Did the practice store the BIs properly?
• Did all the BIs have the same lot number?
• Were the BIs used before their expiration date?
• Was the control strip left unprocessed?
• Were all the BIs mailed back together?
• Were all the BIs incubated at the proper temperature and for the appropriate time?
• Did the unprocessed control BI demonstrate growth after culturing?
• Did the monitoring service microbiologically confirm all positive results?


Charles John Palenik, MS, PhD, is an assistant director of Infection Control Research and Services at the Indiana University School of Dentistry. Dr. Palenik has authored numerous articles, book chapters and monographs, and is the co-author of the popular Infection Control and Management of Hazardous Materials for the Dental Team. He serves on the Executive Board of OSAP, dentistry's resource for infection control and safety.Questions about this article or any infection control issue may be directed to office@osap.org.

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