Submitted to: Environmental Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/16/2008
Publication Date: 3/15/2009
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2285.pdf
Citation: Haznedaroglu, B.Z., Kim, H.N., Bradford, S.A., Walker, S.L. 2009. Relative Transport Behavior of Escherichia coli O157:H7 and Salmonella enterica serovar Pullorum in Packed Bed Column Systems: Influence of Solution Chemistry and Cell Concentration. Environmental Science and Technology. 43(6):1838-1844. Interpretive Summary: Salmonella pullorum and Escherichia coli O157:H7 have been associated with food- and water-borne disease outbreaks in the United States. The objective of this study was to investigate the influence of cell concentration and ionic strengthen on the relative transport and retention of these two bacterial pathogens. Characterization of the cell surface properties was used to help examine differences in transport behavior. Under similar experimental conditions, Salmonella pullorum was transported to a greater extent than E. coli O157:H7 due to its more negative surface charge. Scientist and engineers may use this information to assess the relative risk of Salmonella pullorum and Escherichia coli O157:H7 to food and water supplies.
Technical Abstract: The influence of solution chemistry and cell concentration on bacterial pathogen transport has been examined using Salmonella pullorum and Escherichia coli O157:H7. A packed bed column was employed to determine the transport behavior and deposition kinetics on real aquifer sand particles over a range of electrolyte ionic strength and cell injection concentration. E. coli O157:H7 was found to be more adhesive than S. pullorum, with calculated deposition rate coefficients higher than those of S. pullorum. Comprehensive cell surface characterization techniques including size, surface charge density, extracellular polymeric substance content, electrophoretic mobility, and hydrophobicity analyses were conducted to explain observed transport trends. The two pathogen’s size measurement and hydrophobicity values did not show significant differences; whereas they varied in acidity, for which E. coli O157:H7 had 19 times average higher surface charge density than S. pullorum. Electrophoretic calculations, in general agreement with titration analysis and column experiment results, revealed that the S. pullorum was more negative than E. coli O157:H7. These combinations of column and cell surface characterization experiments indicate that S. pullorum can be transported to a greater extent than E. coli O157:H7 in groundwater environments. This study is the first comprehensive work comparing the transport behavior of two important outbreak causing pathogens in aquifer systems.