Controlling Bacteria In Space
Preventing the spread of bacteria throughout the solar system and protecting the health of human space travelers are important issues that require the control of microbes in spacecraft.
A silane quaternary ammonium salt (QAS) was applied to aluminum and tested against three species of bacteria to determine its value as an antimicrobial surface shield.
Right: Bacteria under microscope
|
|
 |
Methods
Aluminum coupons were treated with the ÆGIS Microbe ShieldTM and the antimicrobial agent’s effectiveness was examined. For one hour, treated and untreated coupons were independently exposed to three types of bacteria: Bacillus subtilis, Staphylococcus epidermidis and Escherichia coli. Bacterial growth was recorded using the pour-plate method
 .
Above: The pour-plate method using tryptic soy agar.
Results
For B. subtilis and S. epidermidis, the numbers of live bacteria were greatly reduced when exposed to the coupons treated with the QAS. The results were inconclusive for E. coli. The effectiveness of the QAS surfacing agent appeared to decline after repeated uses as evidenced by a decreased bacterial killing.
Above: (Left) Setup for surface test and preparation of the initial bacteria concentrations. (Right) Flasks in agitator at T=0 for surface test
Conclusions
The results from the B. subtilis and S. epidermis correlated with the expected antimicrobial effects of the QAS. E. coli, however, was less affected by the treatment. This result is most likely explained by the loss of effectiveness of the QAS after repeated uses. As the aluminum coupons were reused and autoclaved between uses, the activity of the microbe shield seemed to be reduced. This finding is contrary to the company claim that the QAS is non-leaching and permanent. It is supposed to withstand temperatures well over the autoclaving temperature of 121°C. The surface darkened after autoclaving in the spent media, suggesting that some sort of change occurred on the metal.
Acknowledements
Thank you to Randall Sumner and the Environmental Microbiology Laboratory at Kennedy Space Center for assistance and advice in the preparation of this project. Thank you to Jason Johns and Arvye Davis for laboratory assistance and to Adam Santone and Dr. Daniel Woodard for their guidance.
Author: Daniel Blustein, Kalamazoo College
Principal Investigators:
Nona Hinkle, Bionetics Corporation, NASA - Kennedy Space Center
Ami Smith, Bionetics Corporation, NASA - Kennedy Space Center
Click here to download a printable Microsoft PowerPoint version of this research.
|
