Evaluation of a rapid readout biological indicator for 121 degrees C gravity and 132 degrees C vacuum-assisted steam sterilization cycles.
OBJECTIVE
A biological indicator (BI), based on fluorescent detection of a spore-associated enzyme, has been developed. We evaluated the new BI against five conventional self-contained BIs in a 121 degrees C gravity-displacement sterilizer and, packaged in towel packs and disposable steam test packs, in a 132 degrees C vacuum-assisted sterilizer.


METHODS
In the 121 degrees C gravity-displacement sterilizer, rapid readout BIs and conventional BIs were tested together in an otherwise empty chamber. Exposure times were 5, 10, and 15 minutes. In the 132 degrees C vacuum-assisted steam sterilizer, BIs were contained in towel packs or disposable steam test packs. Surgical packs were added to represent a full load. Exposure times were 0, 1, and 2 minutes.


RESULTS
In gravity-displacement 5-minute cycles, the rapid readout BIs yielded 100% positive results within 30 minutes. The conventional BIs ranged from 72% to 100% positive in 48 hours. At 10 minutes, the rapid readout BIs were 83% positive after 3 hours, whereas the conventional BIs ranged from 0% to 37% positive after 48 hours. All indicators were negative after 15-minute exposures. In vacuum-assisted cycles, all indicators were negative after 3 minutes. After 1-minute exposures, the rapid readout BIs were 40% to 60% positive, whereas the conventional BIs were 15% to 20% positive.


CONCLUSIONS
The rapid readout BIs are a more sensitive indicator of marginal steam sterilization cycles than conventional self-contained BIs. They yield results within 3 hours, as compared to 24 to 48 hours for the conventional BIs.
Vesley
D
D
School of Public Health, University of Minnesota, Minneapolis 55455, USA.
Nellis
M A
MA
Allwood
P B
PB
D005069:Evaluation Studies as Topic; D001411:Geobacillus stearothermophilus; D006801:Humans; D007202:Indicators and Reagents; D013170:Spores; D013227:Steam; D013242:Sterilization / Q000295:instrumentation / Q000379:methods*; D013696:Temperature; D013997:Time Factors
D007202:Indicators and Reagents; D013227:Steam