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 ne w BI against five conventional self-contained BIs in a 121 degrees C g ravity-displacement sterilizer and, packaged in towel packs and dispos able steam test packs, in a 132 degrees C vacuum-assisted sterilizer. DESIGN:In the 121 degrees C gravity-displacement sterilizer, rapid rea dout BIs and conventional Bls were tested together in an otherwise emp ty chamber. Exposure times were 5, 10, and 15 minutes. In the 132 degr ees C vacuum-assisted steam sterilizer, BIs were contained in towel pa cks or disposable steam test packs. Surgical packs were added to repre sent a full load. Exposure times were 0, 1, and 2 minutes. RESULTS: In gravity-displacement 5-minute cycles, the rapid readout BIs yielded 1 00% positive results within 30 minutes. The conventional BIs ranged fr om 72% to 100% positive in 48 hours. At 10 minutes, the rapid readout BIs were 83% positive after 3 hours, whereas the conventional BIs rang ed from 0% to 37% positive after 48 hours. All indicators were negativ e after 15-minute exposures. In vacuum-assisted cycles, all indicators were negative after 3 minutes. After 1-minute exposures, the rapid re adout BIs were 40% to 60% positive, whereas the conventional BIs were 15% to 20% positive. CONCLUSION: The rapid readout BIs are a more sens itive indicator of marginal steam sterilization cycles than convention al self-contained BIs. They yield results within 3 hours, as compared to 24 to 48 hours for the conventional BIs.