COMPARISON OF ION-PLASMA, VAPORIZED HYDROGEN-PEROXIDE, AND 100-PERCENT ETHYLENE-OXIDE STERILIZERS TO THE 12 88 ETHYLENE-OXIDE GAS STERILIZER/

OBJECTIVE: The performance of a standard gas sterilizer, which uses a mixture of 12% ethylene oxide (EtO) and 88% chlorofluorocarbon as the sterilizing gas (12/88), was compared to selected gas, ion plasma, and vaporized hydrogen peroxide (H2O2) sterilizers that do not use chloro fluorocarbons. The effect of serum and salt an sterilizer performance was evaluated. DESIGN: Test carriers (porcelain and stainless steel pe nicylinders, or 125-cm lengths of plastic tubing [internal diameter of 3.2 mm]) were inoculated with Escherichia coli, Enterococcus faecalis , Pseudomonas aeruginosa, Mycobacterium chelonei, Bacillus stearotherm ophilus spores, Bacillus subtilis spores, and Bacillus circulans spore s and then subjected to sterilization using 12/88, 100% EtO, ion plasm a, or vaporized H2O2. The bacterial inoculum was prepared with and wit hout 10% serum and 0.65% salt, and the residual bacterial load after s terilization as determined using viable counts. RESULT: All of the ste rilizers tested effected a six-log(50) reduction of the bacterial inoc ulum on penicylinders, unless 10% serum and 0.65% salt were present, i n which case the 100% EtO, vaporized H2O2, and ion plasma sterilizers were not as effective as the 12/88 sterilizer. None of the sterilizers could eradicate 10(6) CFU of all of the bacteria in 10% serum and 0.6 5% salt when inoculated inside a narrow lumen. CONCLUSIONS: The margin of safety for the 100% EtO, vaporized H2O2, and ion plasma sterilizer s is less than that of the 12/88 sterilizer. The inability of all ster ilizers, including the 12/88, to kill organisms in narrow lumens relia bly when serum and salt were present raises concern about the current practice of gas sterilization of flexible endoscopes.