Purpose: To investigate the water quality of vegetable irrigation ponds in the Suwannee River watershed and analyze the relationship between environment factors and the occurrence and distribution of the human pathogens Salmonella spp., Escherichia coli O157:H7 and Campylobacter jejuni.
Methods: Two water samples were collected from each of 10 vegetable irrigation ponds every month from January, 2011. Population densities and/or occurrence of Salmonella, E. coli O157:H7, C. jejuniand 22 environmental variables were measured for each pond. Denaturing gradient gel electrophoresis was conducted for the analysis of bacterial communities. Correlation coefficients were calculated to evaluate the correlations between the environmental factors and the population or occurrence of the three human pathogens. Partial least square analysis was used for discriminant analysis and generating a predictive model.
Results: All ponds were positive for Salmonella and E. coli O157:H7 mainly in summer and fall of 2011. C. jejuni was detected in 9 ponds, especially during spring. Temporal distribution of the pathogens differed among the ponds. Temperature was positively correlated to Salmonella, while dissolved oxygen concentration and oxidation-reduction potential (ORP) were negatively correlated. Presence of Salmonella was related to bacterial community composition. No correlations were found between Salmonella and fecal indicators. Populations of fecal coliforms, copiotrophic bacteria, and temperature were positively correlated to E. coli O157:H7 incidence, while the total nitrogen concentration (TN) and ORP were negatively correlated. TN and ORP were positively correlated to population and occurrence of C. jejuni. The occurrences of E. coli O157:H7 and Salmonellawere positively correlated.
Significance: This research will provide a research-based comparison of indicator organisms and these human pathogens in a major fruit and vegetable growing area.