Bacterial spores as biological indicators for sterilization by low temperature steam and formaldehyde

• Main Author: Hoxey, Eamonn V.
• Published: University of Bath 1984
• Subjects: 579; Microbiology
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.348019

This thesis reports on the study of a number of strains of bacterial spores to identify potential biological indicators for sterilization by Low Temperature Steam and Formaldehyde. The introduction includes a summary of the kinetics of sterilization processes together with methods of process validation including biological monitoring. Current theories explaining the resistance of bacterial spores and factors which affect resistance to both heat and chemicals are discussed. The experimental is divided into five sections. The first reports on the growth and sporulation of twenty strains of Bacillus species on three chemically defined sporulation media and the germination index of the resultant spores. In the second section experiments are reported where the moist heat resistance of these spores in aqueous suspension was determined and spores of six strains were selected for detailed investigation. The moist heat resistance of these spores over a range of temperatures from 120°C to 70°C is then described. The third section reports a detailed investigation into the resistance of B. subtilis Trav 5230 to formaldehyde in aqueous solution and compares the resistance of all six strains to this treatment. The design and construction of an experimental apparatus to expose spores to Low Temperature Steam and Low Temperature Steam and Formaldehyde is then described. The final two experimental sections describe methods used to examine the resistance of spores of the six selected strains to LTS and LTSF using this apparatus. The findings of these experimental sections are discussed in relation to concepts of bacterial spore inactivation and compared to published work.