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.

The influence of solution chemistry and cell concentration on bacterial transport has been examined using Salmonella pullorum SA1685 and Escherichia coli O157:H7. A column was employed to determine the transport behavior and deposition kinetics with aquifer sand over a range of ionic strengths and cell concentrations. O157:H7 was found to be more adhesive than SA1685, with calculated deposition rate coefficients higher than those of SA1685. Comprehensive cell surface characterization techniques including size, surface charge density, extracellular polymeric substance content, electrophoretic mobility, and hydrophobicity analyses were conducted to explain observed transporttrends. The pathogens' size and hydrophobicity were not significantly different, whereas they varied in acidity, for which O157:H7 had 19 times higher surface charge density than SA1685. Electrophoretic mobilities, in general agreement with titration analysis and column experiments, revealed SA1685 to be more negative than O157:H7. This combination of column and characterization experiments indicates that SA1685 can be transported to a greater extent than O157:H7 in groundwater environments. This study is the first comprehensive work comparing the transport behavior of two important pathogens in aquifer systems.