N-184. Factors Affecting Enterococcus-Like Organisms in the Great Salt Lake: Influence of Water Depth, Season and Additional Physical Parameters
Historically, Enterococcus species have been used as indicators of fecal contamination, especially for investigations of longer-term contamination of the water being sampled. Since Enterococcus species are halotolerant and supposedly survive longer than indicator organisms such as Escherichia coli, their presence in the Great Salt Lake (GSL) in Utah is of interest and elucidation of factors which influence their survival in that setting is important. Previous studies in our lab had indicated that the numbers of Enterococcus-like organisms isolated from the GSL marina varied seasonally. Yet, the reasons for these differences were not apparent. Thus, the purpose of this investigation was to study the influence of water depth, seasons and other physical parameters on the numbers of Enterococcus-like organisms isolated from the GSL. A device was made to accurately sample from the surface and specific sub-surface depths. Water samples were collected from the south arm of the GSL near the marina throughout the year. Numbers of Enterococcus-like organisms were determined by membrane filtration using m-Enterococcus agar. Enterococci were identified as Gram positive, catalase negative cocci, which grew on bile esculin agar, hydrolyzing esculin. Physical characteristics of the water such as temperature, salinity and pH were measured. Enumeration of Enterococcus-like organisms indicated that water depth, season of collection, and saline concentration all influence the number of enterococci present in the GSL water. In vitro studies of Enterococcus demonstrated survival for over one week in sterilized GSL water that contained over 10% total dissolved solids. Persistence of Enterococcus-like organisms in the GSL through all seasons suggests that other halotolerant pathogens, such as Staphylococcus aureus, may survive as well. Thus, there is a need to be vigilant about usage of these waters for recreation.