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Journal of Water and Health Vol 10 No 4 pp 504–510 © IWA Publishing 2012 doi:10.2166/wh.2012.084

Solar inactivation of four Salmonella serovars in fresh and marine waters

Alexandria B. Boehm, Cherrie Soetjipto and Dan Wang

Environmental and Water Studies, Department of Civil and Environmental Engineering, Stanford, California 94305 USA E-mail: aboehm@stanford.edu
Dept. Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Y2E2 room 189, Stanford, CA 94305, USA


Sunlight-mediated disinfection of water is of interest to both the drinking and recreational water quality community of researchers due to its potential to reduce microbial contamination and waterborne illness. Photo-inactivation of enteric bacteria has primarily been investigated using Escherichia coli and laboratory strains of model bacteria. The present study sought to document the photo-inactivation of environmental isolates of Salmonella in filter-sterilized natural seawater and freshwater and to test the hypothesis that diverse Salmonella serovars decay at similar rates both within and between water matrices. The inactivation of Salmonella enterica Typhimurium LT2, Typhimurium ST19, Heidelberg, and Mbandaka was examined in sunlit and dark microcosms. First order decay was observed in sunlit microcosms; the time until 90% inactivation was of the order of 10 min. A significant shoulder, of the order of 1 hr in length, was observed in the freshwater microcosms during which concentrations were stable. Serovar Mdandaka decayed more slowly than other serovars in both seawater and freshwater. The serovars were extremely stable in the dark microcosms showing little to no decay over 53 days. The results document intra-species variation in photo-inactivation, likely owing to differences in intracellular concentrations of photo-sensitizing molecules or molecules that quench reactive species.

Keywords: disinfection; enteric pathogens; microbial pollution; photo-inactivation; Salmonella; sunlight

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