Factors that influence the presence of fecal indicator bacteria from three potential exposure pathways

Abstract

Fecal indicator bacteria (FIB) are good predictors for the presence of pathogens associated with fecal contamination in recreational waters and criteria have been created as a benchmark to assess risk to human health. The two most traditionally used FIB for this purpose are culturable Escherichia coli in freshwaters and enterococci in marine settings and members of the Order Bacteroidales have been mentioned heavily in the literature as supplementary indicators. It has been well documented in the literature that fecal indicator bacteria can be modulated by a number of factors, such as temperature, ultraviolet light, land use, and rainfall. This collection of studies yielded information on a how factors could modulate FIB from a variety of transport pathways to human exposure. In surface waters, concentration- and loading-based results for E. coli and Bacteroidales were highest in summer and spring, and lowest in the winter and fall, respectively. Bacteroidales concentrations were positively correlated with temperature and total suspended solids and negatively correlated with dissolved oxygen. In beach sand, E. coli concentrations were highest in the upper 0-10 cm of the foreshore samples where beachgoers typically congregate. For substrate types typically used in stormwater infrastructure, plate count concentrations increased considerably from initial spiking dose, but results were dependent on strain of bacteria and substrate type (concrete, metal, PVC).