Positive Spore Test: What Happens to the Loads and the Patients
You are the lead RDH at a six-operatory practice. On Monday the biological indicator (Geobacillus stearothermophilus spore test) from autoclave #2 came back positive. The office manager says the building's humidity has been high, “it's probably a false positive,” and that staff ran a new cycle Monday night and “the strip looked fine.” Between Monday and Wednesday the practice used instruments from autoclave #2 on 41 patients, and no patients have been contacted. Meanwhile you notice the ultrasonic cleaner has not been drained or disinfected in three weeks, instruments sit in a glutaraldehyde tray that is changed “about monthly,” and staff do not flush handpiece lines between patients. No one keeps a written log of spore tests or of autoclave maintenance.
1. What is the correct immediate response to the positive biological indicator and to the loads and patients involved?
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Take autoclave #2 out of service immediately: tag it, stop running patient loads, and call the service technician. The controlling concept is “last known good” - everything processed in that unit since the last passing biological indicator is suspect.
Sequence:
- Reconstruct. Identify every load between the last negative BI and Monday, what instruments were in each, and which patients were treated with them. Forty-one patients over three days is a starting number, not a rounding error.
- Reprocess anything from those loads still in inventory.
- Notify. The decision to notify patients is a clinical and risk decision made with the dentist and the practice's risk manager or insurer - not a decision for the office manager or a sterilization technician. The default should be transparency: tell patients what happened, what the plausible risk is, and what to watch for.
- Re-challenge before reuse. The unit does not return to service until it is inspected and repaired as needed and challenged with biological indicators that pass, typically consecutive negative runs per the manufacturer's and CDC's guidance.
Your role: escalate in writing, with dates and names, and do not accept “we'll watch it.” If the practice keeps running the unit, decline to treat with instruments from it and consider a complaint to LARA.
2. Evaluate the office manager's reasoning and describe what a defensible sterilization monitoring program looks like.
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The reasoning fails on three counts.
“Probably a false positive.” A biological indicator is the accepted test of whether the sterilizer actually killed spores. A false positive is possible, but it is a laboratory and technique question to be investigated - control organism, incubation temperature, processing error - not a conclusion to assume because investigating is inconvenient.
“The strip looked fine.” This confuses a chemical indicator with a biological one. Chemical indicators show that a package was exposed to heat/steam; they say nothing about whether sterilization occurred. A color change is not evidence of sterility.
“We reran the cycle.” Running one more cycle without repair or investigation is not a re-challenge. The unit needs inspection and documented repeat BI testing before it is trusted again.
A defensible program includes: biological indicators at least weekly and with every load containing implants; a written log recording date, load contents, result, and corrective action; chemical indicators inside and outside every package; cycle parameters (time, temperature, pressure) read and recorded; manufacturer's load configuration and drying times followed; written policy for a positive result; and retention of those logs consistent with the practice's record policy. Ownership matters - if the office manager owns this process, the owner-dentist must be told in writing that the manager's response was inadequate.
3. Address the ultrasonic cleaner, the glutaraldehyde tray, and the handpiece lines. What are the standards, and what are your professional obligations as the hygienist?
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Three separate failures, all upstream or downstream of the sterilizer.
Ultrasonic cleaner. It is a cleaning device and must be drained, cleaned, and disinfected at the manufacturer's specified interval, with the solution changed on schedule. Three weeks of standing solution means instruments come out dirtier than they went in, and the sterilizer downstream is being asked to do work it cannot do - sterilization does not remove debris.
Glutaraldehyde. It is a high-level disinfectant, not a sterilant in the sense staff are using the word. It requires minimum effective concentration testing with test strips (at least daily, more often with heavy use), the labeled immersion time, a covered container, and MIOSHA-compliant handling and ventilation. “Changed about monthly” with no MEC testing is unverifiable and cannot be defended.
Handpiece lines. Flush and maintain per manufacturer instructions between patients; the internal line is a documented source of retraction contamination.
Your obligations. The licensee who uses the instruments is accountable for the chain that produced them. Document the deficiencies with dates, put your concerns to the owner-dentist in writing, and decline to treat with instruments whose sterility you cannot vouch for. If nothing changes, a complaint to LARA is appropriate - Michigan's infection-control requirements for dental settings and MIOSHA's bloodborne pathogens standard are the legal hooks, and “I was just the hygienist” is not a defense the Board has ever accepted.