The use of indicators for quality control of sterilizing processes in hospital practice: a review

The development over the last 100 years of spore preparations to challenge sterilization processes using steam is reviewed briefly, and efforts to standardize such biological indicators (BIs) in the last 30 years are reviewed in more detail. A similar review of BIs for the ethylene oxide processes is presented with discussion of spore test resistances compared to the potential resistances of organisms commonly found as contaminants in the materials being sterilized. The development and need for quick-reading chemical indicators (CIs) that produce color changes only when exposed to moist heat or ethylene oxide plus moisture, as planned, are discussed. It is emphasized that BIs and CIs can only indicate that the sterilization process has worked as planned. They do not indicate that the materials being sterilized are completely sterile.