Title: Comparing dependencies of E. coli, Salmonella, and Enterococci survival on temperature in surface waters Authors
Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: March 29, 2013
Publication Date: April 18, 2013
Citation: Blaustein, R.A., Pachepsky, Y.A., Hill, R., Whelan, G., Shelton, D.R. 2013. Comparing dependencies of E. coli, Salmonella, and Enterococci survival on temperature in surface waters. BARC Poster Day. Technical Abstract: Microbial water quality is attracting substantial attention due to the documented role of produce in microbial food contamination, shellfish industry concerns, and recreation disruptions. In particular, irrigated produce accounted for nearly half of all food-borne illnesses in the USA from 1998 to 2008. E. coli and Enterococci are leading indicators of pathogen presence in waters. Understanding and modeling survival of these organisms is critical for estimating the risk of microbial contamination of water and making appropriate management evaluations. The objectives of this study were to develop models of temperature effects on survival of these microbial indicators in surface waters, and to evaluate the survival of these indicators in comparison to Salmonella survival. We assembled a unique database consisting of approximately 500 survival datasets from peer-reviewed papers on inactivation of E. coli, Salmonella, and Enterococci in water from various sources. We concentrated on 170 inactivation curves taken from experiments performed in laboratories under dark conditions to exclude the effects of sunlight and other field factors that would cause additional variability in the results. The datasets were converted to a format so that “log concentration vs. time” comparisons could be evaluated. About two-fifths of the dependencies began with a section of fast inactivation followed by a section of slow inactivation, just over a quarter were approximately linear throughout, just under a quarter started with a lag period followed by inactivation, and a small number of graphs started with a lag period followed by a section fast inactivation that concluded with a section of slow inactivation. The first order inactivation rate constants were calculated from the approximately linear sections of all survival datasets and the data was grouped into categories based on the origin of the water studied. Data from experiments on rivers, seawater, and estuaries was grouped together for each microorganism in order to make comparisons. Dependencies of the survival of E. coli and Salmonella on temperature in lake water were evaluated. Temperature dependencies of E. coli and Salmonella survival in different water types were also examined. The Q10 temperature-dependence model was applied to the grouped datasets. Dependencies of the inactivation of E. coli, Salmonella, and Enterococci on temperature displayed similar response patterns. Changes in inactivation rates with temperature were generally the same for all microorganisms. However, site-specific variability in the data was observed and illustrated the uncertainty encountered in estimating the risk of microbial contamination in surface waters. This study will be extended to provide additional guidance on the calibration of indicator fate and transport modeling systems that are used to support environmental management decisions regarding the use of surface water sources in agriculture, aquaculture, and recreation.