Sterilization of Products Contaminated with Pyronema domesticum

Product recalls due to non-sterility occurred between 1993 and 1994 among manufacturers that were sterilizing cotton products sourced from China using ethylene oxide (EO). The primary contaminant was identified as a pyrophilous mold from the class Discomycetes, Pyronema domesticum. Multiple references suggest this organism has special needs for reproducing and maintaining the two assumed resistant stages of this organism (ascospores and sclerotia). Sterilization resistance studies were performed using a China-sourced cotton product that was naturally contaminated with P. domesticum. These studies showed the organisms to have: 1) a low resistance to moist heat sterilization at 250°F (121°C); 2) a resistance to radiation no greater than that predicted by the bioburden-based resistance model (i.e., Population C) used for dose determination Method 1 described in ANSI/AAMI/ISO 11137-2:2006—Sterilization of health care products—Radiation—Part 2: Establishing the sterilization dose; and 3) a high resistance to EO processing.