Continuing from our last post around routine monitoring, let’s jump into biological indicators (BI) and process challenge devices (PCD). BIs contain a microorganism resistant to an intended sterilization cycle and are used to confirm its lethality. For terminal sterilization using H2O2, it always contains at least a million viable spores of Geobacillus stearothermophilus. The BI result tells us if the indicator was exposed to conditions sufficient to kill all the spores it contains. Combined with our CI results, we now know two things: the sterilant was present at the CI locations and it was able to kill all organisms in the BI. But what about scopes or hard-to-reach places? Was the cycle capable of getting its deadly sterilant everywhere it needed to go? The BI could have been easier to sterilize than some medical devices, and this is where the PCD completes the picture.
PCDs for H2O2 processes contain a BI and are designed to mimic the resistance to the sterilization process of the most challenging instrument routinely processed. They emulate the toughest maze our sterilant could have to solve, and thus confirm the presence of adequate cycle conditions to sterilize even the most challenging devices. However, knowing that adequate cycle conditions were present is still insufficient to guarantee devices’ sterility, as it also relies on compliance to all previous processing steps (e.g. cleaning), as described in the validated IFUs. Nonetheless, the use of an appropriate PCD containing a BI is a powerful tool for detecting sterilization failure. Even though a PCD should be used at least daily, it is best used in every load.
Altogether, the combination of rigorous validation of the sterilizer cycles, compliance to the validated IFUs and routine monitoring of the sterilization cycle can provide confidence that a sterilization process has successfully rendered a given instrument sterile.