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Applied and Environmental Microbiology, March 2009, p. 1248-1255, Vol. 75, No. 5
0099-2240/09/$08.00+0     doi:10.1128/AEM.01648-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Distribution, Diversity, and Seasonality of Waterborne Salmonellae in a Rural Watershed

Bradd J. Haley,^1, Dana J. Cole,^1,2 and Erin K. Lipp^1*

University of Georgia, Department of Environmental Health Science, Athens, Georgia 30602,¹ Georgia Division of Public Health, Epidemiology Section, Atlanta, Georgia 30303²

Received 17 July 2008/ Accepted 23 December 2008

Salmonella outbreaks from contaminated water and nonanimal foods (e.g., produce) are increasingly reported. To address the environment as a potential source of pathogenic Salmonella, we investigated levels of salmonellae and the geographic and temporal variation of Salmonella serotypes from surface waters in a region of Georgia (United States) with a history of high salmonellosis case rates. Monthly water samples were collected from six stations in the Little River (Upper Suwannee Basin) for 12 months (April 2005 to April 2006). Salmonellae were enumerated using a three-step most-probable-number (MPN) assay. Salmonellae were detected in 57 of the 72 water samples collected (79.2%). Monthly Salmonella densities ranged from an MPN of 2.5 liter^–1 in April 2005 to 36.3 liter^–1 in August 2005; concentrations were significantly higher in the summer months compared to other seasons (P < 0.05). Concentrations were not significantly different between stations. Levels of salmonellae were correlated with average daily watershed rainfall for the 1 and 2 days preceding each sample collection (r = 0.77 and 0.68, respectively; P < 0.005). Additionally, water temperature was also positively associated with total Salmonella levels (r = 0.44; P < 0.05). In total, 13 S. enterica serotypes were identified among 197 Salmonella isolates. Eighty (40.6%) were identified as S. enterica subsp. arizonae. Muenchen and Rubislaw were the most frequently identified serotypes of the remaining 117 isolates (28 and 26 isolates, respectively). Serotype diversity peaked in the summer, with 9 serotypes observed in August compared to only one serotype (S. enterica subsp. arizonae) observed in April (2005 and 2006) (P < 0.05). Furthermore, all samples collected in August (6/6) contained multiple serotypes (two to five per sample). The results of this study suggest that Salmonella abundance and diversity in the environment vary temporally and are strongly influenced by seasonal precipitation and water temperature.

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* Corresponding author. Mailing address: Department of Environmental Health Science, The University of Georgia, 206 Environmental Health Science Bldg., Athens, GA 30602. Phone: (706) 583-8138. Fax: (706) 542-7472. E-mail: elipp{at}uga.edu

Published ahead of print on 5 January 2009.

Present address: College of Life and Chemical Sciences, University of Maryland, 3241 Biosciences Research Building, College Park, MD 20742.

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Applied and Environmental Microbiology, March 2009, p. 1248-1255, Vol. 75, No. 5
0099-2240/09/$08.00+0     doi:10.1128/AEM.01648-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.