Q-215. Culture-Based and Molecular Methods to Determine the Fate of Selected Pathogens when Added as Cross-Contamination Inocula into Space-Mission Simulated Food Trash Compartment Waste

M. P. Hummerick, M. N. Birmele, J. T. Richards, R. F. Strayer, M. S. Roberts;
Dynamac Corp., Kennedy Space Center, FL.

Solid waste treatment technologies are being considered by NASA to reduce microbial loads in solid wastes generated during long-term space travel and habitation. The project objective is to quantify the effect of treatment technologies on microbial fate in food waste stored for varying durations in habitation compartments. Current research is focused on the addition of indicator microorganisms, introduced via cross-contamination from human waste sources, selected to challenge the solid waste treatment technology, and includes those that could be introduced via cross-contamination from human waste sources. Challenge microorganisms included: Escherichia coli, Salmonella enterica serovar typhimurium, Staphylococcus aureus, Aspergillus niger, Pseudomonas aeruginosa, and Bacillus pumilus. B. pumilus has been detected on/in spacecraft and is resistant to UV radiation, desiccation, and heat. All test organisms were confirmed by DNA sequencing. All microbiological and molecular methods were qualified with a preliminary study. Simulated wastes were inoculated with saliva and buccal samples from donors and food waste was inoculated with a mixture of the 6 test microorganisms at 1 x 109 total cells. The inoculated waste was stored at 25 oC for 0 or 7 days in heat sealed foil bags. All selective media were shown to recover the target organism. Colony counts of S. aureus indicated that this organism decreased by 20% between sample days whereas E. coli (Petri film) and S. enterica (Brilliant Green Agar) increased over the 7 day period by between 2 to 3 orders of magnitude. These results indicate that E. coli and S. enterica grew on the food waste. Concentrated community samples from the dilution liquid from day 0 and 7 food wastes were tested by qPCR with species-specific primer sets. All optimized primers were found to successfully detect the specific target microorganism for both days and did not cross-amplify DNA from the non-target test microorganisms. These results will be used to select and optimize pre-storage waste treatment technologies and will provide methods for testing technologies for the ability to limit contaminant survival and growth / proliferation.