B. Atrophaeus and G. Stearothermophilus Biological Indicators for Chlorine Dioxide Gas Decontamination

In anticipation of a validation program for the use of chlorine dioxide (CD) gas in the decontamination of laminar flow biological safety cabinets, the use of Bacillus atrophaeus (BA) and Geobacillus stearothermophilus (GS) endospores for biological indicators (BIs) of CD gas decontaminations were studied. This work includes studies of BIs having either paper or steel substrates. BI analyses were performed with both enumeration and fractionation methods. Among the conclusions it was found that in using paper GS BIs, results from enumeration analysis proved to be too variable to monitor CD decontaminations. Targeted CD exposure levels provided significantly less than a 6-log spore reduction of GS spores on steel substrates, but were very effective for GS BIs with paper substrates. BA spores on paper proved to be suitable and repeatable for validation work with either enumeration or fractionation analysis. Formaldehyde decontamination conditions used in standard practices were largely ineffective to decontaminate the GS indicators.