Q-219. Drought and Storm Impacts on Loading of Salmonella spp. and Campylobacter spp. in a Georgia Coastal Plain Watershed

G. Martin1, D. Cole2,1, E. K. Lipp1;
1Univ. of Georgia, Athens, GA, 2Georgia Dept. of Pub. Hlth., Atlanta, GA.

Salmonella and Campylobacter spp. are among the top enteric food and waterborne disease causing organisms in the United States. Several rural counties in the South Georgia coastal plain, spanned by the Little River Watershed, were identified as reporting the highest salmonellosis rates in the state and far exceeding the national average (78.1 vs. 15.4 per 100,000 people, respectively). Environmental transmission, possibly from contaminated surface waters, is suspected in many of these cases due to their seasonal and sporadic nature and no identified contaminated food source. We hypothesized that microbial loading during storm events may contribute significantly to surface water contamination. The primary objective of this study was to elucidate the effects of discrete storm events on microbial loading of the Little River Watershed. Samples were collected from stations representing 3 different stream orders with varying land use. Baseline samples were collected after at least 7 days of no significant rain. Storm samples were taken after at least a half inch of consistent rainfall. This was adjusted due to a severe drought in Georgia during the last half of 2007, resulting in 23 cm less rain (22% deficit) than the previous 10 year average for this area. Campylobacter levels were determined by direct plating followed by PCR confirmation of suspected colonies. Salmonella spp. were detected using a 5-tube, 3-Step MPN assay; and were confirmed by biochemical testing and serotyping at a commercial reference lab. All data were log transformed to approximate a normal distribution. Over all sites, mean Salmonella storm event levels were significantly higher than baseline samples, 1.06 MPN L-1 vs. 0.44 respectively (p=0.023). Mean Campylobacter storm levels were also higher than baseline levels, 2.22 CFU ml-1 vs.1.05 respectively (p=0.005). One-Way Analysis of Means demonstrated mean Salmonella and Campylobacter levels were higher at lower stream orders (p=0.05), suggesting smaller streams may be more heavily impacted by microbial loading. This study constitutes a step in understanding the effects of climate on environmental levels of these pathogens and the potential impact on human health.