P3-221 Evaluation of E. coli and Other Indicators as Predictors of Foodborne Pathogens in Irrigation Water

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Amy Kahler , Centers for Disease Control and Prevention, Division of Foodborne, Waterborne and Environmental Diseases , Atlanta , GA
Candace Miller , ORISE , Atlanta , GA
Mia Mattioli , Centers for Disease Control and Prevention, Division of Foodborne, Waterborne and Environmental Diseases , Atlanta , GA
Moukaram Tertuliano , University of Georgia , Tifton , GA
Karen Levy , Emory University , Atlanta , GA
George Vellidis , University of Georgia , Tifton , GA
Vincent Hill , Centers for Disease Control and Prevention, Division of Foodborne, Waterborne and Environmental Diseases , Atlanta , GA
Introduction: Currently, produce growers in the U.S. use the fecal indicator bacteria Escherichia coli to evaluate irrigation water quality, using standards developed for recreational water monitoring. Evidence is lacking to demonstrate whether the FSMA E. colistandards accurately reflect the presence of foodborne pathogens in irrigation water. Alternative indicators may provide growers with a better understanding of the microbial quality of water used in produce production.

Purpose: This study examined whether the current E. coli standards were associated with pathogen presence in irrigation water. We then evaluated the utility of E. coli, other traditional fecal indicator microorganisms, and molecular microbial source tracking (MST) markers as tools for predicting the presence of pathogens.

Methods: Irrigation water was collected from three ponds in a southern Georgia growing region over one year. Samples were analyzed for Salmonella and fecal indicators E. coli, enterococci, and male-specific bacteriophages. Samples were also analyzed for MST markers of fecal contamination including: human, avian, ruminant, pig, and chicken specific targets. Logistic and linear regression were conducted to compare detection rates and concentrations of Salmonellaand indicators.

Results: Salmonella presence was not associated with E. coli concentrations above the USEPA recreational water geometric mean standard of 126 MPN/100 mL or the statistical threshold value of 410 MPN/100 mL. There were no associations between the presence of any indicator to Salmonella presence. However, E. coli and enterococci concentrations were positively associated with Salmonella presence. E. coli, enterococci, and bacteriophage concentrations were also positively correlated with Salmonella concentration. The MST markers were not associated with Salmonellapresence or concentration.

Significance: Our results show that recreational water quality standards for E. coli were not predictive of Salmonella presence in the irrigation ponds studied in southern Georgia. Further research is needed to evaluate E. coli guideline values and consider alternative agricultural water quality indicators.