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Sterilization of heat-resistant instruments with infrared radiation
Victor Hugo Mata-Portuguez1, Leonor Sánchez Pérez, Enrique Acosta-Gío
1Microbiology and Infection Control Laboratory, National University of Mexico Dental School, Mexico City.
Objective:
To evaluate the lethality profile of an infrared radiation (IR) prototype sterilizer.
Method:
Simulated use and D value tests were conducted with Bacillus subtilis spores American Type Culture Collection-9372. A spore suspension (1.06 +/- 0.03 x 10(6)) in 5% bovine serum albumin was air dried on stainless steel instruments. IR cycles were completed and the instruments were immersed in tryptic soy broth for 120 hours at 37 degrees C. Direct enumeration of survivors was performed to evaluate IR death. Instrument loads contained carriers laden with spores (1.06 +/- 0.3 x 10(6)). The spores were seeded on tryptic soy agar and survivors were counted after 120 hours of incubation at 37 degrees C.
Results:
All instruments exposed to IR (n = 50) were culture negative. In contrast, all unprocessed instruments (n = 30) showed B. subtilis growth. The prototype's D value was 0.56, and the death rate's slope was -1.76 (r = -0.99741; P < .0001). The 10(6) sterility assurance level was reached after 8 minutes and 40 seconds of exposure, from cold start.
Conclusions:
IR destroys B. subtilis spores. Instrument sterilization with IR may provide another technology for infection control.