Occurrence and Diversity of Enterococci Species in Creeks as Indications of Non-Point Sources of Fecal Contamination.

Tracing non-point sources of water contamination has been a challenge. We hypothesize that the quantity and species diversity of fecal indicator bacteria vary in space and time, which may be linked to potential contamination sources. Enterococci spp. in creeks were evaluated with respect to temporal and spatial variations. From seven sampling sites along three creeks in Stillwater area of central Oklahoma, 42 samples were taken during base-flow; and 21 were taken during the high-flow period. Counts of Enterococci were tested first with the IDEXX Enterolert™ System. A total of 525 Enterococci isolates were obtained from the positive Enterolert™ wells and were subsequently verified by Enterococcosel agar plates (black colonies) and brain heart infusion agar (BHIA) plates supplemented with 6.5% NaCl. Positive isolates were further confirmed to be catalase negative, gram positive, and shown to be spherical or ovoid cells under a phase contrast microscope. Subsequently, these isolates were also confirmed by polymerase chain reaction (PCR) amplification using primers that are specific for Enterococci species. Genetic diversity of the obtained isolates were evaluated by examining internally transcribed spacer (ITS) region by analysis of PCR amplicons obtained using primers that were directed to the ITS region. Overall, 359 out of the 525 isolates obtained were positive Enterococci. Counts of Enterococci ranged from 2.17 to 3.36 log(MPN) 100 mL^-1 in surface water and 4.22 to 6.18 log(MPN) 100 mL^-1 in sediments. All surface water showed Enterococci counts exceeding the recommendation made for recreation water by the United State Environmental Protection Agency and Oklahoma Department of Environmental Quality (DEQ) (<33 counts per 100 mL^-1). Counts of Enterococci in the surface water during high-flow period were approximately 100 times higher than those during base-flow period. Therefore, effective management of storm water is critical in maintaining water quality in the environment.