Entwicklung neuartiger Bioindikatoren für die Dampfsterilisation

Sterilization techniques are used in food and pharmaceutical industries as well as in hygienic areas to protect humans and animals from infections with pathogenic microorganisms. Bioindicators are systems, including selected spore forming microorganisms of the species Bacillus or Geobacillus, which are positioned on a suited carrier. Due to their enormous resistance towards heat and their low pathogenicity, bioindicators are used for the evaluation of sterilization processes. The EN ISO DIN 11138 and 14161 as well as the European pharmacopoeia provide guidance for the manufacturing and the implementation of bioindicators. However, these requirements limit the significance of bioindicators because of their claim to inactivate all appointed spores during sterilization. When a statistically relevant amount of individual populations is used, surviving spores allow not only a qualitative evaluation of the sterilization process but also a quantitative evaluation of the effectiveness. Furthermore, commercially available bioindicators are usually designed in a way so that the sterilizing agent cannot reach all spores equally, due to inhomogeneous application of the spores or the lack of steam penetration into the system. When using those designs, no accurate calculation of the D-value, which is a measure for the spore resistance, is possible because the reproducibility of the cell rate and the resistance is restricted. The existing uncertainties while using bioindicators do not allow users to recognize a lack of quality and testing laboratories to state a comparable result. A correct application and evaluation of bioindicators is therefore not always guarantied. This is why an innovative bioindicator is needed which is able to ease the application and enhance the significance of the used system. This work presents a series of experiments to examine sporulation and germination factors of Geobacillus stearothermophilus. In this process a highly resistant laboratory isolate was identified with a maximum D-value of 4,14 ± 0,11 min. Applying a reasonable initial spore population with such high D-values allows the survival of individual spores. To obtain a homogenous response from the sterilization process the spores were arranged in a monolayer with sufficient liability to the substrate. As the application of individual spore populations is not adequate for the evaluation of the sterilization efficiency, a method was developed during this work to transfer multiple populations on one carrier. Based on this new system an optical evaluation system was devised for the interpretation of the individual populations on that particular bioindicator. The combination of all outcomes presented in this work result in an innovative prototype with seven individual populations positioned on one carrier. This novel bioindicator guaranties the highest possible security for the application and evaluation of sterilization processes