An evaluation of three biological indicator systems in flash sterilization.

An evaluation of two flash-sterilization-specific biological indicators (BI) and a traditional spore strip indicator was performed to assess sensitivity and reliability as reflected in survive/kill ratios. The BIs tested included: 3M's Attest #1261, Amsco's Proof Flash, and Castle Tec Test. Survival after "come-up" time alone, (0 exposure) and one-, two-, and three-minute exposures at 273 degrees F in a gravity displacement sterilizer was measured by media color change or turbidity after incubation at 55 degrees C. Each cycle was replicated three times on two separate days with six of each BI per run. Positive BIs were subcultured as necessary. Proof Flash presented technical difficulties due to incomplete or impossible crushing of media vials, unexpected media color changes, and evaporation of media. Tec Test was not sufficiently resistant as survivors were not detected at any exposure time. The Attest had 100% survival at zero and one-minute exposures and 94% survival after the two-minute exposure. No survivors were detected after the three-minute exposure. Although each institution should evaluate BIs for their own use independently, the data indicate that Attest #1261 monitored the three-minute flash cycles more satisfactorily than the other BIs tested.