miércoles, 18 de abril de 2012

Descontaminación para el espacio

Estación Espacial Internacional
Los actuales métodos de descontaminación para equipo y componentes espaciales utilizan calentamiento seco para reducción microbiana, a temperaturas >110°C por largos periodos para prevenir la contaminación en destinos extraplanetarios. Este proceso es efectivo y reproducible, pero es largo, costoso y excluye su uso en materiales sensibles al calor. Las agencias espaciales han identificado la necesidad de un método alternativo para la reducción microbiana. En este estudio se evaluaron dos procesos de descontaminación gaseosa, peroxido de hidrógeno en vapor y dióxido de cloro, colocados en una cámara de exposición a 20m(3).

Ver la referencia:
Pottage T, Macken S, Giri K, Walker J, Bennett A. Low Temperature Decontamination for Space Applications -- A Comparison of Hydrogen Peroxide and Chlorine Dioxide. Appl Environ Microbiol. 2012 Apr 6.
También recomendamos leer:
Li YJ, Zhu N, Jia HQ, Wu JH, Yi Y, Qi JC. Decontamination of Bacillus subtilis var. niger spores on selected surfaces by chlorine dioxide gas. J Zhejiang Univ Sci B. 2012 Apr;13(4):254-60.
Abstract
The currently used microbial decontamination method for spacecraft and components uses dry heat microbial reduction, at temperatures >110°C for extended periods to prevent contamination of extraplanetary destinations. This process is effective and reproducible, but, is long, costly and precludes the use of heat-labile materials. The need for an alternative to dry heat microbial reduction has been identified by space agencies. Investigations assessing the biological efficacy of two gaseous decontamination technologies, Vapour Hydrogen Peroxide (Steris) and Chlorine Dioxide (ClorDiSys) were undertaken within a 20m(3) exposure chamber. Five spore forming Bacillus spp. were exposed on stainless steel coupons to vaporised hydrogen peroxide and chlorine dioxide gas. Exposure for 20 minutes to vapour hydrogen peroxide resulted in a 6 and 5 log reduction in recovery of Bacillus atrophaeus and Geobacillus stearothermophilus respectively. However, in comparison, chlorine dioxide required an exposure period of 60 minutes to reduce both B. atrophaeus and G. stearothermophilus by 5 logs. Of the 3 other Bacillus spp. tested Bacillus thuringiensis proved the most resistant to hydrogen peroxide and chlorine dioxide with D-values of 175.4 seconds and 6.6 hours respectively. Both low temperature decontamination technologies proved effective at reducing the Bacillus spp. tested within the exposure ranges by over 5 logs with the exception of B. thuringiensis which was more resistant to both technologies. The results highlight that a review of the indicator organism choice and loading could provide a more appropriate and realistic challenge for sterilisation procedures used in the space industry.
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