ABSTRACT
The first use of biological indicators in industrial sterilization is attributed to Kilmer, who inoculated spores of Bacillus anthracis in the center of packages of gauze dressings to verify the efficacy of sterilization (1). Today biological indicators are available in a variety of different formats ranging from spore suspensions employed to inoculate product according to the method pioneered by Kilmer to rapid readout biological indicators that provide an indication of the efficacy of a sterilization process within hours of processing (2). Despite the progress that has been made in the field of biological indicator technology, biological indicators are often a source of frustration to those who are not familiar with their characteristics and idiosyncrasies. As noted by Spicher (3):
We use monitors to obtain objective information on the efficacy of microbiocidal procedures. The judgement of the microorganisms is infallible. In this case the responsibility for any errors rests on the maker of the biological indicators, the employer of the biological indicators, the tester for surviving organisms, namely man, alone! There are numerous opportunities for making errors.
