Monitoring of Decontamination Methods

Biological and chemical indicators are used to monitor the lethality of a sterilization process and ensure the effectiveness of sterilization. They are also used to routinely monitor a sterilizer’s performance according to practices developed and published by the “Association for the Advancement of Medical Instrumentation” (AAMI), the “Association for peri-Operative Registered Nurses” (AORN) and the “Centers for Disease Control” (CDC).
Biological indicators (BI) contain large number of highly resistant spores of Geobacillus stearothermophilus . Destroying and killing of these spores in the BI by the tested sterilization processes implies that the sterilization process is effective enough to kill other potential pathogens. BIs are commercially available as test kits, and they are used to assess the sterility level of water, food containers, and medical and surgical tools and instruments in hospital rooms. When the test kit is incubated, the spores of G.Stearothermophilusgerminate in the kit and produce α-glucosidase enzymes that react with the fluorescent media (4-methyl-umbelliferyl-α-D-glucopyranoside) in the kit and produces a fluorescent signal, which is then detected by the detector in the incubator. The advantage of BIs is that they are quite quick tests, only requiring 20 minutes for both incubation and detection ([BSI], 2014a; ANS, 2017; Gordon, 2013; Swenson, 2012).
In contrast to BIs, chemical indicators (CIs) do not contain resistant spores, and instead use special chemicals or pigments that change physical properties or color when specific environmental conditions have been attained. As such, they are able to monitor decontamination methods based on the fulfillment of one or more of the parameters required for a satisfactory sterilization process. This physical or chemical change is interpreted as a pass or fail result. For example, when using steam for sterilization such as in an autoclave, a solid CI that converts to liquid upon exposure to steam can be used to confirm the quality of sterilization. When pigments are used, they chemically react with some critical parameters of the sterilization process and consequently the color changes to its endpoint color, indicating that the parameters for sterilization have been met. ([BSI], 2001, 2014b; ANS, 2017).