Indicators for sterilization control

To control sterilization cycles, special indicators are used, which can be divided into two groups:

• Biological indicators
• Chemical indicators

Biological indicators

They are indicators that allow us to evaluate the effectiveness of sterilization, therefore the killing of microorganisms in the vegetative or spore phase. In fact, these are bacterial spores inoculated onto different types of support which, in addition to allowing their appropriate use, best emulate the process that leads to the reduction of the microbial load. The spores are selected by type and above all resistance to specific sterilizing agents, such as steam, dry heat, ethylene oxide, radiation, etc.

Strip, spore suspensions, ampoules, self-containde indicators, discs...

Chemical indicators

These are a wide variety of indicators based on the reactivity of color changing inks; one part simply has the function of indicating that exposure to the sterilization process has taken place, they essentially serve to distinguish products that have undergone the cycle from those that have not. An example is the indicator tape that is applied to baskets or packages of material to be sterilized. Other systems, however, show greater sensitivity, reacting with the color change only in the presence of certain minimum conditions relating to the critical parameters of the cycle, for example specific combinations of time-temperature-quality of the steam in the case of steam sterilization. ISO 11140-1:2005 defines a non-hierarchical subdivision into 6 classes, which allows chemical indicators to be distinguished based on their purpose.

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