Spores sterilization monitoring

Section Val. 1900 includes four aseptic processes associated with monitoring and qualification programs covering determination of components bioburden before sterilization sterility test failure investigation, bacterial endotoxin determination in WFI, in-process finished product, and monitoring the bioburden, spore bioburden, and endotoxin present on stoppers and unprocessed vials. 

In other words, the D-value is a function of the previous history of the monitor as well as of the sterilizer in which it was determined. The composition of the fluid from which the spores were dried may also influence D-values by coating the spores with a layer of material through which moisture or ethylene oxide may have restricted permeability. This also gives importance to the conditions in which the spores were grown (complex or defmed media) and washed. Graham [10] quotes D-values of 2.4 min and 3.S min for the same strain of B. subtilis var niger grown in different liquid media and exposed to ethylene oxide under identical conditions. 

Graham, G. (1986). Production of spores and preparation of spore suspensions and monitors. In Proceedings of EUCOMED Workshop on Biological Monitoring of Sterilization. Kerkrade, Netherlands, April 21-23, 1986. 

Biological indicators (i.e. preparations of bacteria cultures, usually spore of selected resistant strains) are must less reliable than physical monitoring methods, except in Ethylene Oxide Sterilization. 

C. Quantitative Studies. Quantitative studies were initiated in order to quantify the extent of microbial growth on polymer surfaces. In the first set of quantitative studies, turbidity was used as an indicator of microbial growth. Polymer films were cast in the base of sterile 150 mL bottles. Sterile buffer (100 mL) and an A, niger spore suspension (1 X 10 spores) were poured over the films. Turbidity was monitored each day for two weeks by removing a small sample (3 mL) from each bottle and measuring its change in optical density (580 nm) on a Bausch and Lomb Spectronic 21. Controls were included to correct for the contribution of buffer and polymer to turbidity. All experiments were done at room temperature. 

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