Alternative fast analysis method for cellulose sponge surface sampling wipes with low concentrations of Bacillus Spores

Abstract

Environmental sampling is a critical component of the post decontamination verification process following a bioterrorism event. The current work was performed to produce a less labor-intensive method for processing cellulose sponge-wipes used for sampling areas potentially contaminated with low concentrations (i.e., post-decontamination) of Bacillus anthracis spores. An alternative fast-analysis processing method was compared to the processing protocol validated by the Centers for Disease Control and Prevention (CDC) for the Laboratory Response Network (LRN). Glazed tile coupons (1102 cm2) were inoculated with 50, 500, or 5000 spores of Bacillus thuringiensis subsp. kurstaki (Btk), then sampled with cellulose sponges. Sampling was limited to a 25- by 25-cm area and performed in the same manner as the CDC sampling method. Samples were then processed using either the alternative “Fast Analysis” method or the “CDC method”. Three different analysts repeated the tests at each concentration utilizing each method. Mean recoveries, labor time, and potentially hazardous waste produced were compared for the two methods. The mean percent recoveries and standard errors for the samples processed using the “CDC method” were 39.9 ± 6.7, 43 ± 7.6, and 36.8 ± 10.1 for the 5000, 500, and 50 spore loading levels, respectively; compared to 54.2 ± 12.9, 64.2 ± 21.7, and 45.2 ± 8.6 for the “Fast Analysis” method. At each titer tested the “Fast Analysis” method resulted in a statistically significant higher percent recovery. Furthermore, analysts processed samples utilizing the “Fast Analysis” method in less than half the time and generated half as much potentially hazardous waste compared to the “CDC method”.