Practical Matters: Routinely assess sterilizer efficacy with indicator strips and spore tests

Jul 01, 2005

To be sure that an entire surgical pack has been sterilized, place indicator tape on the outside of surgical packs and indicator strips on the inside, as well. We use different chemical indicator strips inside the packs than the tape used on the outside to give us increased evaluation of sterilization, and we use appropriate indicator strips for each type of sterilizer used (steam, gas, chemical). The strips indicate whether proper sterilization parameters (temperature, pressure, concentration, time, humidity) have been met inside the surgical packs.

Make sure to check these indicators before beginning a surgical procedure. Do not open any other surgical items or begin the surgery until the internal indicators have been checked and are satisfactory. Periodically, we have found that the internal strips do not adequately change color, even though the outer tapes have changed, indicating that proper sterilization temperature, time, concentration, or pressure was not reached.

We also test the sterilizers weekly with spore tests. These are the definitive tests for sterility. These tests consist of spores of Bacillus atrophaeus (highly resistant to ethylene oxide gas and dry heat) and Geobacillus stearothermophilus (highly resistant to moist heat and chemical vapors). If the sterilization parameters are not met, the bacteria will grow, indicating a problem with the sterilizer that should be checked.

Dean Gahring, DVM, DACVS
San Carlos Veterinary Hospital
8618 Lake Murray Blvd.
San Diego, CA 92119