Predicting Salmonella Populations from Biological, Chemical, and Physical Indicators in Florida Surface Waters

Abstract

ABSTRACTColiforms,Escherichia coli, and various physicochemical water characteristics have been suggested as indicators of microbial water quality or index organisms for pathogen populations. The relationship between the presence and/or concentration ofSalmonellaand biological, physical, or chemical indicators in Central Florida surface water samples over 12 consecutive months was explored. Samples were taken monthly for 12 months from 18 locations throughout Central Florida (n= 202). Air and water temperature, pH, oxidation-reduction potential (ORP), turbidity, and conductivity were measured. Weather data were obtained from nearby weather stations. Aerobic plate counts and most probable numbers (MPN) forSalmonella,E. coli, and coliforms were performed. Weak linear relationships existed between biological indicators (E. coli/coliforms) andSalmonellalevels (R2< 0.1) and between physicochemical indicators andSalmonellalevels (R2< 0.1). The average rainfall (previous day, week, and month) before sampling did not correlate well with bacterial levels. Logistic regression analysis showed thatE. coliconcentration can predict the probability of enumerating selectedSalmonellalevels. The lack of good correlations between biological indicators andSalmonellalevels and between physicochemical indicators andSalmonellalevels shows that the relationship between pathogens and indicators is complex. However,Escherichia coliprovides a reasonable way to predictSalmonellalevels in Central Florida surface water through logistic regression.