Q-236. Monitoring the Pathogenicity and Transport Behavior of Escherichia coli O157:H7 and Salmonella enterica spp. in Packed Bed Column Systems

B. Z. Haznedaroglu, S. L. Walker;
Univ. of California, Riverside, CA.

This comprehensive study focuses on bacterial transport and the extent of pathogenicity in groundwater. The intention was to determine to what extent solution chemistry and cell concentration affect transport trends and pathogenicity of Escherichia coli and Salmonella. For this purpose, S. pullorum, S. typhimurium (wild type and dysfunctional flagellated mutant strain), and E. coli O157:H7 were injected into a packed bed column with real aquifer sand over a range of solution ionic strength. Pathogenicity, antibiotic resistance, and in vitro infectivity assays (inoculating Hep-2 cell lines) were conducted with bacteria exposed to groundwater for various time periods and solution chemistry. Transport experiments showed that E. coli O157:H7 was more adhesive than S. pullorum, with deposition rate coefficients calculated for E. coli O157:H7 higher than those of S. pullorum. Comprehensive cell surface characterization techniques including size, surface charge density, extracellular polymeric substances, electrophoretic mobility, and hydrophobicity analyses were conducted to explain observed transport trends. The two pathogens’ size measurement and hydrophobicity values did not show differences, whereas they varied in acidity with E. coli O157:H7 having a higher surface charge density than S. pullorum. Electrophoretic mobility calculations, in agreement with titration analysis and column experiment results, revealed that than S. pullorum was more electronegative than E. coli O157:H7. Packed bed column and cell surface characterization experiments indicate that S. pullorum can be transported more than E. coli O157:H7 in groundwater environments. These results agree with travel distances calculated theoretically. Initial studies of antibiotic resistance show dysfunctional flagellated mutant strain of S. typhimurium is more resistant to several antibiotics than the wild type. The findings of this study contribute to the understanding of fate and transport of important pathogens in groundwater.