A failed biological indicator is a documentation event before it is a sterility event. When a BC dental clinic received a positive spore test on a Monday morning, the logbook, not the sterilizer, told them what had happened: the load had been a full, tightly packed cassette cycle run at the end of the day, and the indicator had been placed on the chamber floor rather than inside a process challenge device. The clinic repeated the cycle with a fresh indicator in a PCD, recorded a negative result, and the sterilizer returned to service the same day. This case review walks through the investigation in the order the team actually worked it, because the sequence is what keeps a single positive from turning into a closed operatory.
What should a clinic do first when a biological indicator fails?
The first move is quarantine, not disassembly. Instruments from the affected load are held, not used and not discarded, because a positive result does not automatically mean the instruments are contaminated — it means the cycle result is unverified. The sterilizer is taken out of service, the load is labelled with the date and cycle number, and the logbook is pulled so the physical evidence can be read alongside the result.
In the BC case, the team also photographed the chamber and the load configuration before anything was moved. That single step is why the root cause was identifiable within an hour instead of a day.
Which physical factors do most investigation protocols check?
After quarantine, the checklist is mechanical and repeatable. The usual order is:
- Was the biological indicator inside a process challenge device, and was it placed where the load is hardest to penetrate?
- Was the chamber loaded within the manufacturer's stated capacity, or was it packed to the door?
- Did the cycle reach the correct temperature and pressure for the full holding time?
- Was the indicator within its expiry date and stored away from heat and moisture?
- Was the incubator at the correct temperature, and was a control indicator run?
Most positives traced in dental settings resolve to load configuration or indicator placement rather than a mechanical failure. That pattern matters for Canadian clinics because the RCDSO requires a biological indicator for each sterilizer on every day it is used — daily monitoring, not weekly. The weekly baseline is the CDC / AAMI ST79 standard in most US states, so teams that read American guidance can under-test without realising it.
| Investigation step | What it rules out | Typical record kept |
|---|---|---|
| Quarantine the load | Unverified instruments entering use | Load label, date, cycle number |
| Check PCD placement | Indicator in a non-challenging position | Photo, placement note |
| Review chamber load | Overloading and blocked steam penetration | Load diagram |
| Verify cycle parameters | Aborted or shortened cycle | Cycle printout or chart |
| Re-run with fresh indicator | Persistent sterilizer fault | Repeat result and control |
What changed at the BC clinic afterwards?
Three changes came out of the review, and none of them required new equipment. First, every wrapped load now carries an indicator inside a process challenge device in the emptiest part of the chamber, not on the floor. Second, the clinic set a hard ceiling on cassette loads and stopped adding one more tray at the end of the day. Third, the spore test result is entered in the logbook at the moment it is read, with the incubator temperature beside it, so the record and the result cannot drift apart.
The follow-up period was uneventful. The clinic has kept the same sterilizer, the same pouch brand and the same staff; what changed was the discipline around placement, load size and record keeping.
Related reading
Sterilization compliance hub; sterilizer validation versus routine monitoring; a Canadian lab spore test failure review; 24-hour rapid-readout biological indicators. Ordering for a clinic, lab or care home? Wholesale and multi-site ordering covers case pricing and account setup, and the B2B wholesale collection lists the lines stocked for institutional buyers.
Frequently Asked Questions
Can we use the instruments from a load with a positive spore test?
No. Hold the load until a repeat cycle with a fresh indicator, placed in a process challenge device, gives a negative result with a valid control. Record the repeat result beside the original in the logbook.
How often must a dental office run a spore test in Ontario?
The RCDSO requires a biological indicator for each sterilizer on every day it is used — daily monitoring, not weekly. The weekly baseline is the CDC / AAMI ST79 standard in most US states.
Does a single positive result mean the sterilizer is broken?
Usually not. Most investigated positives trace to indicator placement or load configuration rather than a mechanical fault. A repeat cycle with a correctly placed indicator is what confirms the sterilizer is working.
CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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